[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]
Subject: Re: [virtio-dev] [RFC PATCH v3] virtio-blk: add zoned block device specification
On Thu, 4 Aug 2022 at 18:41, Dmitry Fomichev <dmitry.fomichev@wdc.com> wrote: Hi Dmitry, I think RFC can be removed from the Subject line for the next revision of this patch. For instructions on how to bring this to a Technical Committee vote, see: https://github.com/oasis-tcs/virtio-spec#use-of-github-issues > > Introduce support for Zoned Block Devices to virtio. > > Zoned Block Devices (ZBDs) aim to achieve a better capacity, latency > and/or cost characteristics compared to commonly available block > devices by getting the entire LBA space of the device divided to block > regions that are much larger than the LBA size. These regions are > called zones and they can only be written sequentially. More details > about ZBDs can be found at > > https://zonedstorage.io/docs/introduction/zoned-storage . > > In its current form, the virtio protocol for block devices (virtio-blk) > is not aware of ZBDs but it allows the guest to successfully scan a > host-managed drive provided by the host. As the result, the > host-managed drive appears at the guest as a regular drive that will > operate erroneously under the most common write workloads. > > To fix this, the virtio-blk protocol needs to be extended to add the > capabilities to convey the zone characteristics of host ZBDs to the > guest and to provide the support for ZBD-specific commands - Report > Zones, four zone operations and (optionally) Zone Append. The proposed > standard extension aims to provide this functionality. > > This patch extends the virtio-blk section of virtio specification with > the minimum set of requirements that are necessary to support ZBDs. > The resulting device model is a subset of the models defined in ZAC/ZBC > and ZNS standards documents. The included functionality mirrors > the existing Linux kernel block layer ZBD support and should be > sufficient to handle the host-managed and host-aware HDDs that are on > the market today as well as ZNS SSDs that are entering the market at > the moment of this patch submission. > > I have developed a proof of concept patch series that adds ZBD support > to virtio-blk Linux kernel driver by implementing the protocol > extensions defined in the spec patch. I would like to receive feedback > on this specification patch before posting that series to the block > LKML. > > I would like to thank the following people for their useful feedback > and suggestions while working on the initial iterations of this patch. > > Damien Le Moal <damien.lemoal@opensource.wdc.com> > Matias Bjørling <Matias.Bjorling@wdc.com> > Niklas Cassel <Niklas.Cassel@wdc.com> > Hans Holmberg <Hans.Holmberg@wdc.com> > > v1 -> v2: > > Address Stefan's review comments: > > - move normative clauses to normative sections > > - remove the "partial" bit in zone report > > - change layout of virtio_blk_zoned_req. The "all" flag becomes a bit > in "zone" bit field struct. This leaves 31 bits for potential future > extensions. Move the status byte to be the last one in the struct > > - set ZBD-specific error codes in the status field, not in > "zoned_result" field. The former "zoned_result" member now becomes > "append_sector" > > - make a few editorial changes > > v2 -> v3: > > A few changes made as the result of off-list discussions with Stefan, > Damien and Hannes: > > - drop virtblk_zoned_req for zoned devices and define a union for > virtio request in header that is specific to ZONE APPEND request > > - drop support for ALL bit in all zone operations except for RESET > ZONE. For this zone management operation, define a new request type, > VIRTIO_BLK_T_ZONE_RESET_ALL. This way, the zone management out > request header is no longer necessary > > - editorial changes > > Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com> > --- > content.tex | 660 +++++++++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 658 insertions(+), 2 deletions(-) > > diff --git a/content.tex b/content.tex > index 7508dd1..cfb8727 100644 > --- a/content.tex > +++ b/content.tex > @@ -4557,6 +4557,13 @@ \subsection{Feature bits}\label{sec:Device Types / Block Device / Feature bits} > maximum erase sectors count in \field{max_secure_erase_sectors} and > maximum erase segment number in \field{max_secure_erase_seg}. > > +\item[VIRTIO_BLK_F_ZONED(17)] Device is a Zoned Block Device, that is, a device > + that follows the zoned storage device behavior that is also supported by > + industry standards such as the T10 Zoned Block Command standard (ZBC r05) or > + the NVMe(TM) NVM Express Zoned Namespace Command Set Specification 1.1b > + (ZNS). For brevity, these standard documents are referred as "ZBD standards" > + from this point on in the text. > + > \end{description} > > \subsubsection{Legacy Interface: Feature bits}\label{sec:Device Types / Block Device / Feature bits / Legacy Interface: Feature bits} > @@ -4589,6 +4596,75 @@ \subsection{Device configuration layout}\label{sec:Device Types / Block Device / > \field{max_secure_erase_sectors} \field{secure_erase_sector_alignment} are expressed > in 512-byte units if the VIRTIO_BLK_F_SECURE_ERASE feature bit is negotiated. > > +If the VIRTIO_BLK_F_ZONED feature is negotiated, then in > +\field{virtio_blk_zoned_characteristics}, > +\begin{itemize} > +\item \field{zone_sectors} value is expressed in 512-byte sectors. > +\item \field{max_append_sectors} value is expressed in 512-byte sectors. > +\item \field{write_granularity} value is expressed in bytes. > +\end{itemize} > + > +The \field{model} field in \field{zoned} may have the following values: > +VIRTIO_BLK_Z_NONE(0), VIRTIO_BLK_Z_HM(1) and VIRTIO_BLK_Z_HA(2). > + > +\begin{lstlisting} > +#define VIRTIO_BLK_Z_NONE 0 > +#define VIRTIO_BLK_Z_HM 1 > +#define VIRTIO_BLK_Z_HA 2 > +\end{lstlisting} > + > +Depending on their design, zoned block devices may follow several possible > +models of operation. The three models that are standardized for ZBDs are > +drive-managed, host-managed and host-aware. > + > +While being zoned internally, drive-managed ZBDs behave exactly like regular, > +non-zoned block devices. For the purposes of virtio standardization, > +drive-managed ZBDs can always be treated as non-zoned devices. These devices > +have the VIRTIO_BLK_Z_NONE model value set in the \field{model} field in > +\field{zoned}. > + > +Devices that offer VIRTIO_BLK_F_ZONED feature while reporting VIRTIO_BLK_Z_NONE > +zoned model commonly do so for testing and development purposes. > + > +Host-managed zoned block devices have their LBA range divided to Sequential > +Write Required (SWR) zones that require some additional handling from the host > +for sustainable operation. All write requests to SWR zones must be sequential > +and the zones with some data need to be reset before that data can be rewritten. > +Host-managed devices support a set of ZBD-specific I/O requests that can be used > +by the host to manage device zones. Host-managed devices report VIRTIO_BLK_Z_HM > +in the \field{model} field in \field{zoned}. > + > +Host-aware zoned block devices have their LBA range divided to Sequential > +Write Preferred (SWP) zones that support the random write access, similar to > +regular non-zoned devices. However, the device I/O performance might not be > +optimal if SWP zones are used in a random I/O pattern. SWP zones also support > +the same set of ZBD-specific I/O requests as host-managed devices that allow > +host-aware devices to be managed by any host that supports zoned block devices > +to achieve its optimum performance. Host-aware devices report VIRTIO_BLK_Z_HA > +in the \field{model} field in \field{zoned}. > + > +Both SWR zones and SWP zones are sometimes referred as sequential zones. > + > +During device operation, sequential zones can be in one of the following states: > +empty, implicitly-open, explicitly-open, closed and full. The state machine that > +governs the transitions between these states is described later in this document. > + > +SWR and SWP zones consume volatile device resources while being in certain > +states and the device may set limits on the number of zones that can be in these > +states simultaneously. > + > +Zoned block devices use two internal counters to account for the device > +resources in use, the number of currently open zones and the number of currently > +active zones. > + > +Any zone state transition from a state that doesn't consume a zone resource to a > +state that consumes the same resource increments the internal device counter for > +that resource. Any zone transition out of a state that consumes a zone resource > +to a state that doesn't consume the same resource decrements the counter. Any > +request that causes the device to exceed the reported zone resource limits is > +terminated by the device with a "zone resources exceeded" error as defined for > +specific commands later. > + > \begin{lstlisting} > struct virtio_blk_config { > le64 capacity; > @@ -4623,6 +4699,15 @@ \subsection{Device configuration layout}\label{sec:Device Types / Block Device / > le32 max_secure_erase_sectors; > le32 max_secure_erase_seg; > le32 secure_erase_sector_alignment; > + struct virtio_blk_zoned_characteristics { > + le32 zone_sectors; > + le32 max_open_zones; > + le32 max_active_zones; > + le32 max_append_sectors; > + le32 write_granularity; > + u8 model; > + u8 unused2[3]; > + } zoned; > }; > \end{lstlisting} > > @@ -4686,6 +4771,10 @@ \subsection{Device Initialization}\label{sec:Device Types / Block Device / Devic > \field{secure_erase_sector_alignment} can be used by OS when splitting a > request based on alignment. > > +\item If the VIRTIO_BLK_F_ZONED feature is negotiated, the fields in > + \field{zoned} can be read by the driver to determine the zone > + characteristics of the device. All \field{zoned} fields are read-only. > + > \end{enumerate} > > \drivernormative{\subsubsection}{Device Initialization}{Device Types / Block Device / Device Initialization} > @@ -4701,6 +4790,30 @@ \subsection{Device Initialization}\label{sec:Device Types / Block Device / Devic > The driver MUST NOT read \field{writeback} before setting > the FEATURES_OK \field{device status} bit. > > +Drivers SHOULD NOT negotiate VIRTIO_BLK_F_ZONED feature if they are incapable > +of supporting devices with the VIRTIO_BLK_Z_HM or VIRTIO_BLK_Z_HA zoned model. > + > +If the VIRTIO_BLK_F_ZONED feature is offered by the device with the > +VIRTIO_BLK_Z_HM zone model, then > +\begin{itemize} > +\item the VIRTIO_BLK_F_DISCARD feature must not be offered by the driver. > + > +\item if the driver sets both VIRTIO_BLK_F_DISCARD and VIRTIO_BLK_F_ZONED > + feature bits, the device must fail by not setting FEATURES_OK bit. > +\end{itemize} > + > +If the VIRTIO_BLK_F_ZONED feature is negotiated, then > +\begin{itemize} > +\item if the driver that can not support host-managed zoned devices > + reads VIRTIO_BLK_Z_HM from the \field{model} field of \field{zoned}, the > + driver MUST NOT set FEATURES_OK flag and instead set the FAILED bit. > + > +\item if the driver that can not support support zoned devices reads > + VIRTIO_BLK_Z_HA from the \field{model} field of \field{zoned}, the driver > + MAY handle the device as a non-zoned device. In this case, the > + driver SHOULD ignore all other fields in \field{zoned}. > +\end{itemize} > + > \devicenormative{\subsubsection}{Device Initialization}{Device Types / Block Device / Device Initialization} > > Devices SHOULD always offer VIRTIO_BLK_F_FLUSH, and MUST offer it > @@ -4712,6 +4825,74 @@ \subsection{Device Initialization}\label{sec:Device Types / Block Device / Devic > The device MUST initialize padding bytes \field{unused0} and > \field{unused1} to 0. > > +If the device that is being initialized is a not a zoned device, the device > +SHOULD NOT offer the VIRTIO_BLK_F_ZONED feature. > + > +If the VIRTIO_BLK_F_ZONED bit is not set by the driver, > +\begin{itemize} > +\item the device with the VIRTIO_BLK_Z_HA zone model SHOULD proceed with the > + initialization while setting all zoned characteristics fields to zero. > + > +\item the device with the VIRTIO_BLK_Z_HM zone model MUST fail to set the > + FEATURES_OK device status bit when the driver writes the Device Status > + field. > +\end{itemize} > + > +If the VIRTIO_BLK_F_ZONED feature is negotiated, then the \field{model} field in > +\field{zoned} struct in the configuration space MUST be set by the device > +\begin{itemize} > +\item to the value of VIRTIO_BLK_Z_NONE if it operates as a drive-managed > + zoned block device or a non-zoned block device. > + > +\item to the value of VIRTIO_BLK_Z_HM if it operates as a host-managed zoned > + block device. > + > +\item to the value of VIRTIO_BLK_Z_HA if it operates as a host-aware zoned > + block device. > +\end{itemize} > + > +If the VIRTIO_BLK_F_ZONED feature is negotiated, > +\begin{itemize} > +\item the \field{zone_sectors} field of \field{zoned} MUST be set by the device > + to the size of a single zone on the device. All zones of the device have the > + same size indicated by \field{zone_sectors} except for the last zone that > + MAY be smaller than all other zones. The driver can calculate the number of > + zones on the device as > + \begin{lstlisting} > + nr_zones = (capacity + zone_sectors - 1) / zone_sectors; > + \end{lstlisting} > + and the size of the last zone as > + \begin{lstlisting} > + zs_last = capacity - (nr_zones - 1) * zone_sectors; > + \end{lstlisting} > + > +\item The \field{max_open_zones} field of the \field{zoned} structure MUST be > + set by the device to the maximum number of zones that can be open on the > + device (zones in the implicit open or explicit open state). A value > + of zero indicates that the device does not have any limit on the number of > + open zones. > + > +\item The \field{max_active_zones} field of the \field{zoned} structure MUST > + be set by the device to the maximum number zones that can be active on the > + device (zones in the implicit open, explicit open or closed state). A value > + of zero indicates that the device does not have any limit on the number of > + active zones. > + > +\item the \field{max_append_sectors} field of \field{zoned} MUST be set by > + the device to the maximum data size of a VIRTIO_BLK_T_ZONE_APPEND request > + that can be successfully issued to the device. The value of this field MUST > + NOT exceed the \field{seg_max} * \field{size_max} value. A device MAY set > + the \field{max_append_sectors} to zero if it doesn't support > + VIRTIO_BLK_T_ZONE_APPEND requests. > + > +\item the \field{write_granularity} field of \field{zoned} MUST be set by the > + device to the offset and size alignment constraint for VIRTIO_BLK_T_OUT > + and VIRTIO_BLK_T_ZONE_APPEND requests issued to a sequential zone of the > + device. > + > +\item the device MUST initialize padding bytes \field{unused2} to 0. > +\end{itemize} > + > \subsubsection{Legacy Interface: Device Initialization}\label{sec:Device Types / Block Device / Device Initialization / Legacy Interface: Device Initialization} > > Because legacy devices do not have FEATURES_OK, transitional devices > @@ -4738,7 +4919,8 @@ \subsubsection{Legacy Interface: Device Initialization}\label{sec:Device Types / > \subsection{Device Operation}\label{sec:Device Types / Block Device / Device Operation} > > The driver queues requests to the virtqueues, and they are used by > -the device (not necessarily in order). Each request is of form: > +the device (not necessarily in order). If the VIRTIO_BLK_F_ZONED feature > +is not negotiated, then each request is of form: Is this sentence still needed? This revision of the spec seems to use struct virtio_blk_req for both zoned and non-zoned devices, so I think this sentence can be dropped. > > \begin{lstlisting} > struct virtio_blk_req { > @@ -4746,7 +4928,15 @@ \subsection{Device Operation}\label{sec:Device Types / Block Device / Device Ope > le32 reserved; > le64 sector; > u8 data[]; > - u8 status; > + union { > + u8 status; > + > + struct { > + u8 status; > + u8 reserved[3]; > + le64 append_sector; Align to 8 bytes instead of 4 bytes so that append_sector has natural alignment? > + } zone_append_in_hdr; > + }; > }; > \end{lstlisting} > > @@ -4853,6 +5043,290 @@ \subsection{Device Operation}\label{sec:Device Types / Block Device / Device Ope > command produces VIRTIO_BLK_S_IOERR. A segment may have completed > successfully, failed, or not been processed by the device. > > +The following requirements only apply if the VIRTIO_BLK_F_ZONED feature is > +negotiated. > + > +In addition to the request types defined for non-zoned devices, the type of the > +request can be a zone report (VIRTIO_BLK_T_ZONE_REPORT), an explicit zone open > +(VIRTIO_BLK_T_ZONE_OPEN), an explicit zone close (VIRTIO_BLK_T_ZONE_CLOSE), a > +zone finish (VIRTIO_BLK_T_ZONE_FINISH), a zone_append > +(VIRTIO_BLK_T_ZONE_APPEND), a zone reset (VIRTIO_BLK_T_ZONE_RESET) or a zone > +reset all (VIRTIO_BLK_T_ZONE_RESET_ALL). > + > +\begin{lstlisting} > +#define VIRTIO_BLK_T_ZONE_APPEND 15 > +#define VIRTIO_BLK_T_ZONE_REPORT 16 > +#define VIRTIO_BLK_T_ZONE_OPEN 18 > +#define VIRTIO_BLK_T_ZONE_CLOSE 20 > +#define VIRTIO_BLK_T_ZONE_FINISH 22 > +#define VIRTIO_BLK_T_ZONE_RESET 24 > +#define VIRTIO_BLK_T_ZONE_RESET_ALL 26 > +\end{lstlisting} > + > +Requests of type VIRTIO_BLK_T_OUT, VIRTIO_BLK_T_ZONE_OPEN, > +VIRTIO_BLK_T_ZONE_CLOSE, VIRTIO_BLK_T_ZONE_FINISH, VIRTIO_BLK_T_ZONE_APPEND, > +VIRTIO_BLK_T_ZONE_RESET or VIRTIO_BLK_T_ZONE_RESET_ALL may be completed by the > +device with VIRTIO_BLK_S_OK, VIRTIO_BLK_S_IOERR or VIRTIO_BLK_S_UNSUPP > +\field{status}, or, additionally, with VIRTIO_BLK_S_ZONE_INVALID_CMD, > +VIRTIO_BLK_S_ZONE_UNALIGNED_WP, VIRTIO_BLK_S_ZONE_OPEN_RESOURCE or > +VIRTIO_BLK_S_ZONE_ACTIVE_RESOURCE ZBD-specific status codes. > + > +\begin{lstlisting} > +#define VIRTIO_BLK_S_ZONE_INVALID_CMD 3 > +#define VIRTIO_BLK_S_ZONE_UNALIGNED_WP 4 > +#define VIRTIO_BLK_S_ZONE_OPEN_RESOURCE 5 > +#define VIRTIO_BLK_S_ZONE_ACTIVE_RESOURCE 6 > +\end{lstlisting} > + > +Requests of the type VIRTIO_BLK_T_ZONE_REPORT are reads and requests of the type > +VIRTIO_BLK_T_ZONE_APPEND transfer data from the device. VIRTIO_BLK_T_ZONE_OPEN, > +VIRTIO_BLK_T_ZONE_CLOSE, VIRTIO_BLK_T_ZONE_FINISH, VIRTIO_BLK_T_ZONE_RESET and > +VIRTIO_BLK_T_ZONE_RESET_ALL are non-data requests. > + > +In ZBD standards, the VIRTIO_BLK_T_ZONE_REPORT request belongs to "Zone > +Management Receive" command category and VIRTIO_BLK_T_ZONE_OPEN, > +VIRTIO_BLK_T_ZONE_CLOSE, VIRTIO_BLK_T_ZONE_FINISH and > +VIRTIO_BLK_T_ZONE_RESET/VIRTIO_BLK_T_ZONE_RESET_ALL requests are categorized as > +"Zone Management Send" commands. VIRTIO_BLK_T_ZONE_APPEND is categorized > +separately from the zone management commands and is the only request that uses > +\field{zone_append_in_hdr} structure in \field{virtio_blk_req} to return > +to the driver the sector at which the data has been appended to the zone. > + > +VIRTIO_BLK_T_ZONE_REPORT is a read request that returns the information about > +the current state of zones on the device starting from the zone containing the > +\field{sector} of the request. The report consists of a header followed by zero > +or more zone descriptors. > + > +A zone report reply has the following structure: > + > +\begin{lstlisting} > +struct virtio_blk_zone_report { > + le64 nr_zones; > + u8 reserved[56]; > + struct virtio_blk_zone_descriptor zones[]; > +}; > +\end{lstlisting} > + > +The device sets the \field{nr_zones} field in the report header to the number of > +fully transferred zone descriptors in the data buffer. > + > +A zone descriptor has the following structure: > + > +\begin{lstlisting} > +struct virtio_blk_zone_descriptor { > + le64 z_cap; > + le64 z_start; > + le64 z_wp; > + u8 z_type; > + u8 z_state; > + u8 reserved[38]; > +}; > +\end{lstlisting} > + > +The zone descriptor field \field{z_type} \field{virtio_blk_zone_descriptor} > +indicates the type of the zone. The available types are VIRTIO_BLK_ZT_CONV(1), > +VIRTIO_BLK_ZT_SWR(2) or VIRTIO_BLK_ZT_SWP(3). > + > +\begin{lstlisting} > +#define VIRTIO_BLK_ZT_CONV 1 > +#define VIRTIO_BLK_ZT_SWR 2 > +#define VIRTIO_BLK_ZT_SWP 3 > +\end{lstlisting} > + > +Read and write operations into zones with the VIRTIO_BLK_ZT_CONV (Conventional) > +type have the same behavior as read and write operations on a regular block > +device. Any block in a conventional zone can be read or written at any time and > +in any order. > + > +Zones with VIRTIO_BLK_ZT_SWR can be read randomly, but must be written > +sequentially at a certain point in the zone called the Write Pointer (WP). With > +every write, the Write Pointer is incremented by the number of sectors written. > + > +Zones with VIRTIO_BLK_ZT_SWP can be read randomly and should be written > +sequentially, similarly to SWR zones. However, SWP zones can accept random write > +operations, that is, VIRTIO_BLK_T_OUT requests with a start sector different > +from the zone write pointer position. > + > +The field \field{z_state} of \field{virtio_blk_zone_descriptor} indicates the > +state of the device zone. The available zone states are VIRTIO_BLK_ZS_NOT_WP(0), > +VIRTIO_BLK_ZS_EMPTY(1), VIRTIO_BLK_ZS_IOPEN(2), VIRTIO_BLK_ZS_EOPEN(3), > +VIRTIO_BLK_ZS_CLOSED(4), VIRTIO_BLK_ZS_RDONLY(13), VIRTIO_BLK_ZS_FULL(14) and > +VIRTIO_BLK_ZS_OFFLINE(15). > + > +\begin{lstlisting} > +#define VIRTIO_BLK_ZS_NOT_WP 0 > +#define VIRTIO_BLK_ZS_EMPTY 1 > +#define VIRTIO_BLK_ZS_IOPEN 2 > +#define VIRTIO_BLK_ZS_EOPEN 3 > +#define VIRTIO_BLK_ZS_CLOSED 4 > +#define VIRTIO_BLK_ZS_RDONLY 13 > +#define VIRTIO_BLK_ZS_FULL 14 > +#define VIRTIO_BLK_ZS_OFFLINE 15 > +\end{lstlisting} > + > +Zones of the type VIRTIO_BLK_ZT_CONV are always reported by the device to be in > +the VIRTIO_BLK_ZS_NOT_WP state. Zones of the types VIRTIO_BLK_ZT_SWR and > +VIRTIO_BLK_ZT_SWP can not transition to the VIRTIO_BLK_ZS_NOT_WP state. > + > +Zones in VIRTIO_BLK_ZS_EMPTY (Empty), VIRTIO_BLK_ZS_IOPEN (Implicitly Open), > +VIRTIO_BLK_ZS_EOPEN (Explicitly Open) and VIRTIO_BLK_ZS_CLOSED (Closed) state > +are writable, but zones in VIRTIO_BLK_ZS_RDONLY (Read-Only), VIRTIO_BLK_ZS_FULL > +(Full) and VIRTIO_BLK_ZS_OFFLINE (Offline) state are not. The write pointer > +value (\field{z_wp}) is not valid for Read-Only, Full and Offline zones. > + > +The zone descriptor field \field{z_cap} contains the maximum number of 512-byte > +sectors that are available to be written with user data when the zone is in the > +Empty state. This value shall be less than or equal to the \field{zone_sectors} > +value in \field{virtio_blk_zoned_characteristics} structure in the device > +configuration space. > + > +The zone descriptor field \field{z_start} contains the 64-bit address of the > +first 512-byte sector of the zone. > + > +The zone descriptor field \field{z_wp} contains the 64-bit sector address where > +the next write operation for this zone should be issued. This value is undefined > +for conventional zones and for zones in VIRTIO_BLK_ZS_RDONLY, VIRTIO_BLK_ZS_FULL > +and VIRTIO_BLK_ZS_OFFLINE state. > + > +Depending on their state, zones consume resources as follows: > +\begin{itemize} > +\item a zone in VIRTIO_BLK_ZS_IOPEN and VIRTIO_BLK_ZS_EOPEN state consumes one > + open zone resource and, additionally, > + > +\item a zone in VIRTIO_BLK_ZS_IOPEN, VIRTIO_BLK_ZS_EOPEN and > + VIRTIO_BLK_ZS_CLOSED state consumes one active resource. > +\end{itemize} > + > +Attempts for zone transitions that violate zone resource limits must fail with > +VIRTIO_BLK_S_ZONE_OPEN_RESOURCE or VIRTIO_BLK_S_ZONE_ACTIVE_RESOURCE > +\field{status}. > + > +Zones in the VIRTIO_BLK_ZS_EMPTY (Empty) state have the write pointer value > +equal to the start sector of the zone. In this state, the entire capacity of the > +zone is available for writing. A zone can transition from this state to > +\begin{itemize} > +\item VIRTIO_BLK_ZS_IOPEN when a successful VIRTIO_BLK_T_OUT request or > + VIRTIO_BLK_T_ZONE_APPEND with a non-zero data size is received for the zone. > + > +\item VIRTIO_BLK_ZS_EOPEN when a successful VIRTIO_BLK_T_ZONE_OPEN request is > + received for the zone > +\end{itemize} > + > +When a VIRTIO_BLK_T_ZONE_RESET request is issued to an Empty zone, the request > +is completed successfully and the zone stays in the VIRTIO_BLK_ZS_EMPTY state. > + > +Zones in the VIRTIO_BLK_ZS_IOPEN (Implicitly Open) state transition from > +this state to > +\begin{itemize} > +\item VIRTIO_BLK_ZS_EMPTY when a successful VIRTIO_BLK_T_ZONE_RESET request is > + received for the zone, > + > +\item VIRTIO_BLK_ZS_EOPEN when a successful VIRTIO_BLK_T_ZONE_OPEN request is > + received for the zone, > + > +\item VIRTIO_BLK_ZS_CLOSED when a successful VIRTIO_BLK_T_ZONE_CLOSE request is > + received for the zone, > + > +\item VIRTIO_BLK_ZS_CLOSED implicitly by the device when another zone is > + entering the VIRTIO_BLK_ZS_IOPEN or VIRTIO_BLK_ZS_EOPEN state and the number > + of currently open zones is at \field{max_open_zones} limit, > + > +\item VIRTIO_BLK_ZS_FULL when a successful VIRTIO_BLK_T_ZONE_FINISH request is > + received for the zone. > + > +\item VIRTIO_BLK_ZS_FULL when a successful VIRTIO_BLK_T_OUT or > + VIRTIO_BLK_T_ZONE_APPEND request that causes the zone to reach its writable > + capacity is received for the zone. > +\end{itemize} > + > +Zones in the VIRTIO_BLK_ZS_EOPEN (Explicitly Open) state transition from > +this state to > +\begin{itemize} > +\item VIRTIO_BLK_ZS_EMPTY when a successful VIRTIO_BLK_T_ZONE_RESET request is > + received for the zone, > + > +\item VIRTIO_BLK_ZS_EMPTY when a successful VIRTIO_BLK_T_ZONE_CLOSE request is > + received for the zone and the write pointer of the zone has the value equal > + to the start sector of the zone, > + > +\item VIRTIO_BLK_ZS_CLOSED when a successful VIRTIO_BLK_T_ZONE_CLOSE request is > + received for the zone and the zone write pointer is larger then the start > + sector of the zone, > + > +\item VIRTIO_BLK_ZS_FULL when a successful VIRTIO_BLK_T_ZONE_FINISH request is > + received for the zone, > + > +\item VIRTIO_BLK_ZS_FULL when a successful VIRTIO_BLK_T_OUT or > + VIRTIO_BLK_T_ZONE_APPEND request that causes the zone to reach its writable > + capacity is received for the zone. > +\end{itemize} > + > +When a VIRTIO_BLK_T_ZONE_EOPEN request is issued to an Explicitly Open zone, the > +request is completed successfully and the zone stays in the VIRTIO_BLK_ZS_EOPEN > +state. > + > +Zones in the VIRTIO_BLK_ZS_CLOSED (Closed) state transition from this state > +to > +\begin{itemize} > +\item VIRTIO_BLK_ZS_EMPTY when a successful VIRTIO_BLK_T_ZONE_RESET request is > + received for the zone, > + > +\item VIRTIO_BLK_ZS_IOPEN when a successful VIRTIO_BLK_T_OUT request or > + VIRTIO_BLK_T_ZONE_APPEND with a non-zero data size is received for the zone. > + > +\item VIRTIO_BLK_ZS_EOPEN when a successful VIRTIO_BLK_T_ZONE_OPEN request is > + received for the zone, > +\end{itemize} > + > +When a VIRTIO_BLK_T_ZONE_CLOSE request is issued to a Closed zone, the request > +is completed successfully and the zone stays in the VIRTIO_BLK_ZS_CLOSED state. > + > +Zones in the VIRTIO_BLK_ZS_FULL (Full) state can transition from this state to > +VIRTIO_BLK_ZS_EMPTY when a successful VIRTIO_BLK_T_ZONE_RESET request is > +received for the zone > + > +When a VIRTIO_BLK_T_ZONE_FINISH request is issued to a Full zone, the request > +is completed successfully and the zone stays in the VIRTIO_BLK_ZS_FULL state. > + > +The device may automatically transition zones to VIRTIO_BLK_ZS_RDONLY > +(Read-Only) or VIRTIO_BLK_ZS_OFFLINE (Offline) state from any other state. The > +device may also automatically transition zones in the Read-Only state to the > +Offline state. Zones in the Offline state may not transition to any other state. > +Such automatic transitions usually indicate hardware failures. The previously > +written data may only be read from zones in the Read-Only state. Zones in the > +Offline state can not be read or written. > + > +VIRTIO_BLK_S_ZONE_UNALIGNED_WP is set by the device when the request received > +from the driver attempts to perform a write to an SWR zone and at least one of > +the following conditions is met: > + > +\begin{itemize} > +\item the starting sector of the request is not equal to the current value of > + the zone write pointer. > + > +\item the ending sector of the request data multiplied by 512 is not a multiple > + of the value reported by the device in the field \field{write_granularity} > + in the device configuration space. > +\end{itemize} > + > +VIRTIO_BLK_S_ZONE_OPEN_RESOURCE is set by the device when a zone operation or > +write request received from the driver can not be handled without exceeding the > +\field{max_open_zones} limit value reported by the device in the configuration > +space. > + > +VIRTIO_BLK_S_ZONE_ACTIVE_RESOURCE is set by the device when a zone operation or > +write request received from the driver can not be handled without exceeding the > +\field{max_active_zones} limit value reported by the device in the configuration > +space. > + > +A zone transition request that leads to both the \field{max_open_zones} and the > +\field{max_active_zones} limits to be exceeded is terminated by the device with > +VIRTIO_BLK_S_ZONE_ACTIVE_RESOURCE \field{status} value. > + > +The device SHALL report all other error conditions related to zoned block model > +operation by setting the VIRTIO_BLK_S_ZONE_INVALID_CMD value in > +\field{status} of \field{virtio_blk_req} structure. > + > \drivernormative{\subsubsection}{Device Operation}{Device Types / Block Device / Device Operation} > > A driver MUST NOT submit a request which would cause a read or write > @@ -4899,6 +5373,51 @@ \subsection{Device Operation}\label{sec:Device Types / Block Device / Device Ope > successfully, failed, or were processed by the device at all if the request > failed with VIRTIO_BLK_S_IOERR. > > +The following requirements only apply if the VIRTIO_BLK_F_ZONED feature is > +negotiated. > + > +When forming a VIRTIO_BLK_T_ZONE_REPORT request, the driver sets the sector > +address of the starting zone to report to \field{sector}. This is not a MUST/SHOULD/MAY statements. This is a clue that some of these paragraphs should be moved to the non-normative section that describes how things work. The normative sections only have requirements for device and driver implementors, they don't explain how the device works. > + > +VIRTIO_BLK_T_ZONE_OPEN, VIRTIO_BLK_T_ZONE_CLOSE, VIRTIO_BLK_T_ZONE_FINISH and > +VIRTIO_BLK_T_ZONE_RESET requests make the zone operation to act on a particular > +zone specified by the zone sector address in the \field{sector} of the request. > +The zone sector address is a 64-bit value expressed in 512-byte units that > +points at the first sector in the target zone. Normally the struct virtio_blk_req sector field is expressed in bytes. If I'm interpreting this text correctly the zone management commands change the field's meaning to sector units? > + > +VIRTIO_BLK_T_ZONE_RESET_ALL request acts upon all applicable zones of the > +device. For this request, the driver MUST set the field \field{sector} to zero > +value. > + > +The \field{sector} field of the VIRTIO_BLK_T_ZONE_APPEND request MUST specify > +the first sector of the zone to which data is to be appended at the position of > +the write pointer. The zone sector address is a 64-bit value expressed in > +512-byte units that points anywhere in the target zone. The size of the data This "512-byte units" wording confuses me. I think the units should be bytes and the text should say "in multiples of 512 bytes". > +that is appended MUST NOT exceed the \field{max_append_sectors} value provided > +by the device in \field{virtio_blk_zoned_characteristics} configuration space > +structure. > + > +Upon a successful completion of a VIRTIO_BLK_T_ZONE_APPEND request, the driver > +SHOULD read the starting sector location of the written data from the request field > +\field{append_sector}. Maybe that depends on the application? If the application blindly appends and doesn't use the write pointer then there's no need to read append_sector. I think this statement can be removed and instead the non-normative section can describe the purpose of the append_sector field so that driver authors know the new write pointer value is available if they require it. > + > +All VIRTIO_BLK_T_OUT requests issued by the driver to sequential zones and > +VIRTIO_BLK_T_ZONE_APPEND requests MUST have: > + > +\begin{enumerate} > +\item the data size that is a multiple of the number of bytes reported > + by the device in the field \field{write_granularity} in the > + \field{virtio_blk_zoned_characteristics} configuration space structure. > + > +\item the value of the field \field{sector} that is a multiple of the number of > + bytes reported by the device in the field \field{write_granularity} in the > + \field{virtio_blk_zoned_characteristics} configuration space structure. > + > +\item the data size that will not exceed the writable zone capacity when its > + value is added to the current value of the write pointer of the zone. > + > +\end{enumerate} > + > \devicenormative{\subsubsection}{Device Operation}{Device Types / Block Device / Device Operation} > > A device MUST set the \field{status} byte to VIRTIO_BLK_S_IOERR > @@ -4990,6 +5509,143 @@ \subsection{Device Operation}\label{sec:Device Types / Block Device / Device Ope > simplfy passthrough implementations from eMMC devices. > \end{note} > > +If the VIRTIO_BLK_F_ZONED feature is not negotiated, the device MUST reject > +VIRTIO_BLK_T_ZONE_REPORT, VIRTIO_BLK_T_ZONE_OPEN, VIRTIO_BLK_T_ZONE_CLOSE, > +VIRTIO_BLK_T_ZONE_FINISH, VIRTIO_BLK_T_ZONE_APPEND, VIRTIO_BLK_T_ZONE_RESET and > +VIRTIO_BLK_T_ZONE_RESET_ALL requests with VIRTIO_BLK_S_UNSUPP status. > + > +The following device requirements only apply if the VIRTIO_BLK_F_ZONED feature > +is negotiated. > + > +If a request of type VIRTIO_BLK_T_ZONE_OPEN, VIRTIO_BLK_T_ZONE_CLOSE, > +VIRTIO_BLK_T_ZONE_FINISH or VIRTIO_BLK_T_ZONE_RESET is issued for a Conventional > +zone (type VIRTIO_BLK_ZT_CONV), the device MUST complete the request with > +VIRTIO_BLK_S_ZONE_INVALID_CMD \field{status}. > + > +If the zone specified by the VIRTIO_BLK_T_ZONE_APPEND request is not a SWR zone, > +then the request SHALL be completed with VIRTIO_BLK_S_ZONE_INVALID_CMD > +\field{status}. > + > +The device handles a VIRTIO_BLK_T_ZONE_OPEN request with the by attempting to > +change the state of the zone with the \field{sector} address to > +VIRTIO_BLK_ZS_EOPEN. If the transition to this state can not be performed, the > +request MUST be completed with VIRTIO_BLK_S_ZONE_INVALID_CMD \field{status}. If, > +while processing this request, the available zone resources are insufficient, > +then the zone state does not change and the request MUST be completed with > +VIRTIO_BLK_S_ZONE_OPEN_RESOURCE or VIRTIO_BLK_S_ZONE_ACTIVE_RESOURCE value in > +the field \field{status}. > + > +The device handles a VIRTIO_BLK_T_ZONE_CLOSE request by attempting to change the > +state of the zone with the \field{sector} address to VIRTIO_BLK_ZS_CLOSED. If > +the transition to this state can not be performed, the request MUST be completed > +with VIRTIO_BLK_S_ZONE_INVALID_CMD value in the field \field{status}. > + > +The device handles a VIRTIO_BLK_T_ZONE_FINISH request by attempting to change > +the state of the zone with the \field{sector} address to VIRTIO_BLK_ZS_FULL. If > +the transition to this state can not be performed, the zone state does not > +change and the request MUST be completed with VIRTIO_BLK_S_ZONE_INVALID_CMD > +value in the field \field{status}. > + > +The device handles a VIRTIO_BLK_T_ZONE_RESET request by attempting to change the > +state of the zone with the \field{sector} address to VIRTIO_BLK_ZS_EMPTY state. > +If the transition to this state can not be performed, the zone state does not > +change and the request MUST be completed with VIRTIO_BLK_S_ZONE_INVALID_CMD > +value in the field \field{status}. > + > +The device handles a VIRTIO_BLK_T_ZONE_RESET_ALL request by transitioning all > +sequential device zones in VIRTIO_BLK_ZS_IOPEN, VIRTIO_BLK_ZS_EOPEN, > +VIRTIO_BLK_ZS_CLOSED and VIRTIO_BLK_ZS_FULL state to VIRTIO_BLK_ZS_EMPTY state. > + > +Upon receiving a VIRTIO_BLK_T_ZONE_APPEND request or a VIRTIO_BLK_T_OUT > +request issued to a SWR zone in VIRTIO_BLK_ZS_EMPTY or VIRTIO_BLK_ZS_CLOSED > +state, the device attempts to perform the transition of the zone to > +VIRTIO_BLK_ZS_IOPEN state before writing data. This transition may fail due to > +insufficient open and/or active zone resources available on the device. In this > +case, the request MUST be completed with VIRTIO_BLK_S_ZONE_OPEN_RESOURCE or > +VIRTIO_BLK_S_ZONE_ACTIVE_RESOURCE value in the \field{status}. > + > +If the \field{sector} field in the VIRTIO_BLK_T_ZONE_APPEND request does not > +specify the lowest sector for a zone, then the request SHALL be completed with > +VIRTIO_BLK_S_ZONE_INVALID_CMD value in \field{status}. > + > +A VIRTIO_BLK_T_ZONE_APPEND request or a VIRTIO_BLK_T_OUT request that has the > +data range that that exceeds the remaining writable capacity for the zone, then > +the request SHALL be completed with VIRTIO_BLK_S_ZONE_INVALID_CMD value in > +\field{status}. > + > +If a request of the type VIRTIO_BLK_T_ZONE_APPEND is completed with > +VIRTIO_BLK_S_OK status, the field \field{append_sector} in > +\field{zone_append_in_hdr} field in \field{virtio_blk_req} MUST be set by > +the device to contain the start sector of the data written to the zone. > + > +A VIRTIO_BLK_T_ZONE_APPEND request that has the data size that exceeds > +\field{max_append_sectors} configuration space value, then, > +\begin{itemize} > +\item if \field{max_append_sectors} configuration space value is reported as > + zero by the device, the request SHALL be completed with VIRTIO_BLK_S_UNSUPP > + \field{status}. > + > +\item if \field{max_append_sectors} configuration space value is reported as > + a non-zero value by the device, the request SHALL be completed with > + VIRTIO_BLK_S_ZONE_INVALID_CMD \field{status}. > +\end{itemize} > + > +If a VIRTIO_BLK_T_ZONE_APPEND request, a VIRTIO_BLK_T_IN request or a > +VIRTIO_BLK_T_OUT request issued to a SWR zone has the range that has sectors in > +more than one zone, then the request SHALL completed with > +VIRTIO_BLK_S_ZONE_INVALID_CMD value in the field \field{status}. > + > +A VIRTIO_BLK_T_OUT request that has the \field{sector} value that is not aligned > +with the write pointer for the zone, then the request SHALL completed with > +VIRTIO_BLK_S_ZONE_UNALIGNED_WP value in the field \field{status}. > + > +In order to avoid resource-related errors while opening zones implicitly, the > +device MAY automatically transition zones in VIRTIO_BLK_ZS_IOPEN state to > +VIRTIO_BLK_ZS_CLOSED state. > + > +All VIRTIO_BLK_T_OUT requests or VIRTIO_BLK_T_ZONE_APPEND requests issued > +to a zone in the VIRTIO_BLK_ZS_RDONLY state SHALL be completed with > +VIRTIO_BLK_S_ZONE_INVALID_CMD \field{status}. > + > +All requests issued to a zone in the VIRTIO_BLK_ZS_OFFLINE state SHALL be > +completed with VIRTIO_BLK_S_ZONE_INVALID_CMD value in the field \field{status}. > + > +The device MUST consider the data that is read above the write pointer of a zone > +as unwritten data. The sectors between the write pointer position and the upper > +write boundary of the zone during VIRTIO_BLK_T_ZONE_FINISH request processing > +are also considered unwritten data. > + > +When unwritten data is present in the sector range of a read request, the device > +MUST process this data in one of the following ways - > + > +\begin{enumerate} > +\item Fill the unwritten data with a device-specific byte pattern. The > +configuration, control and reporting of this byte pattern is beyond the scope > +of this standard. This is the preferred approach. > + > +\item Fail the request. Depending on the driver implementation, this may prevent > +the device from becoming operational. > + > +\item Return stale, previously written data to the driver. This approach is the > +least preferred for its obvious negative security implications. > +\end{enumerate} Do these semantics come from the ZBD model? They seem kind of undesirable to me (filling with zeroes seems most sensible), but virtio-blk devices must be able to pass through real ZBD devices, so it makes sense to support same semantics as the ZBD model. > + > +If the both VIRTIO_BLK_F_ZONED and VIRTIO_BLK_F_SECURE_ERASE features are > +negotiated, then > + > +\begin{enumerate} > +\item the field \field{secure_erase_sector_alignment} in the configuration space > +of the device MUST be a multiple of \field{zone_sectors} value reported in the > +device configuration space. > + > +\item the data size in VIRTIO_BLK_T_SECURE_ERASE requests MUST be a multiple of > +\field{zone_sectors} value in the device configuration space. > +\end{enumerate} > + > +The device MUST handle a VIRTIO_BLK_T_SECURE_ERASE request in the same way it > +handles VIRTIO_BLK_T_ZONE_RESET request for the zone range specified in the > +VIRTIO_BLK_T_SECURE_ERASE request. > + > \subsubsection{Legacy Interface: Device Operation}\label{sec:Device Types / Block Device / Device Operation / Legacy Interface: Device Operation} > When using the legacy interface, transitional devices and drivers > MUST format the fields in struct virtio_blk_req > -- > 2.34.1 >
Attachment:
signature.asc
Description: PGP signature
[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]