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Subject: RE: [PATCH v5] virtio-blk: add secure erase feature to specification
> From: Yadong Qi <yadong.qi@intel.com>
>
> There are user requests to use the Linux BLKSECDISCARD ioctl on virtio-blk
> device. A secure discard is the same as a regular discard except that all copies of
> the discarded blocks that were possibly created by garbage collection must also
> be erased. This requires support from the device. And "secure erase" is more
> commonly used in industry to name this feature. Hence in this proposal, extend
> virtio-blk protocol to support secure erase command.
>
> Introduced new feature flag and command type:
> VIRTIO_BLK_F_SECURE_ERASE
> VIRTIO_BLK_T_SECURE_ERASE
>
> This feature is a passthrough feature on backend because it is hard to emulate a
> secure erase. So virtio-blk will report this feature to guest OS if backend device
> support such kind of feature. And when guest OS issues a secure erase command,
> backend driver will passthrough the command to host device blocks.
>
> Introduced new fields in virtio_blk_config for secure erase commands:
> struct virtio_blk_config {
> ...
> max_secure_erase_sectors;
> max_secure_erase_seg;
> secure_erase_sector_alignment;
> };
>
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/125
> Signed-off-by: Yadong Qi <yadong.qi@intel.com>
> ---
> v1 -> v2:
> - add separated queue limits for secure discard.
>
> v2 -> v3:
> - reword "secure discard" to "secure erase".
> - adjust offset of new fields
>
> v3 -> v4
> - unify the wording to "secure erase"
>
> v4 -> v5
> - fix typo
> - adjust position of changelog
>
> ---
> content.tex | 41 +++++++++++++++++++++++++++++++++--------
> 1 file changed, 33 insertions(+), 8 deletions(-)
>
> diff --git a/content.tex b/content.tex
> index 5d112af..d380c51 100644
> --- a/content.tex
> +++ b/content.tex
> @@ -4435,6 +4435,11 @@ \subsection{Feature bits}\label{sec:Device Types /
> Block Device / Feature bits}
>
> \item[VIRTIO_BLK_F_LIFETIME (15)] Device supports providing storage lifetime
> information.
> +
> +\item[VIRTIO_BLK_F_SECURE_ERASE (16)] Device supports secure erase
> command,
> + maximum erase sectors count in \field{max_secure_erase_sectors} and
> + maximum erase segment number in \field{max_secure_erase_seg}.
> +
> \end{description}
>
> \subsubsection{Legacy Interface: Feature bits}\label{sec:Device Types / Block
> Device / Feature bits / Legacy Interface: Feature bits} @@ -4463,7 +4468,9 @@
> \subsection{Device configuration layout}\label{sec:Device Types / Block Device
> / \field{discard_sector_alignment} are expressed in 512-byte units if the
> VIRTIO_BLK_F_DISCARD feature bit is negotiated. The
> \field{max_write_zeroes_sectors} is expressed in 512-byte units if the
> VIRTIO_BLK_F_WRITE_ZEROES feature -bit is negotiated.
> +bit is negotiated. The parameters in the configuration space of the
> +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.
>
> \begin{lstlisting}
> struct virtio_blk_config {
> @@ -4496,6 +4503,9 @@ \subsection{Device configuration
> layout}\label{sec:Device Types / Block Device /
> le32 max_write_zeroes_seg;
> u8 write_zeroes_may_unmap;
> u8 unused1[3];
> + le32 max_secure_erase_sectors;
> + le32 max_secure_erase_seg;
> + le32 secure_erase_sector_alignment;
> };
> \end{lstlisting}
>
> @@ -4552,6 +4562,13 @@ \subsection{Device Initialization}\label{sec:Device
> Types / Block Device / Devic \item If the VIRTIO_BLK_F_MQ feature is
> negotiated, \field{num_queues} field
> can be read to determine the number of queues.
>
> +\item If the VIRTIO_BLK_F_SECURE_ERASE feature is negotiated,
> + \field{max_secure_erase_sectors} and \field{max_secure_erase_seg} can be
> read
> + to determine the maximum secure erase sectors and maximum number of
> + secure erase segments for the block driver to use.
> + \field{secure_erase_sector_alignment} can be used by OS when splitting a
> + request based on alignment.
> +
> \end{enumerate}
>
> \drivernormative{\subsubsection}{Device Initialization}{Device Types / Block
> Device / Device Initialization} @@ -4619,7 +4636,8 @@ \subsection{Device
> Operation}\label{sec:Device Types / Block Device / Device Ope The type of the
> request is either a read (VIRTIO_BLK_T_IN), a write (VIRTIO_BLK_T_OUT), a
> discard (VIRTIO_BLK_T_DISCARD), a write zeroes
> (VIRTIO_BLK_T_WRITE_ZEROES), a flush (VIRTIO_BLK_T_FLUSH), a get device ID
> -string command (VIRTIO_BLK_T_GET_ID), or a get device lifetime command
> +string command (VIRTIO_BLK_T_GET_ID), a secure erase
> +(VIRTIO_BLK_T_SECURE_ERASE), or a get device lifetime command
> (VIRTIO_BLK_T_GET_LIFETIME).
>
> \begin{lstlisting}
> @@ -4630,6 +4648,7 @@ \subsection{Device Operation}\label{sec:Device
> Types / Block Device / Device Ope #define VIRTIO_BLK_T_GET_LIFETIME 10
> #define VIRTIO_BLK_T_DISCARD 11
> #define VIRTIO_BLK_T_WRITE_ZEROES 13
> +#define VIRTIO_BLK_T_SECURE_ERASE 14
> \end{lstlisting}
>
> The \field{sector} number indicates the offset (multiplied by 512) where @@ -
> 4641,9 +4660,11 @@ \subsection{Device Operation}\label{sec:Device Types /
> Block Device / Device Ope requests write the contents of \field{data} to the
> block device (in multiples of 512 bytes).
>
> -The \field{data} used for discard or write zeroes commands consists of one or -
> more segments. The maximum number of segments is \field{max_discard_seg}
> for -discard commands and \field{max_write_zeroes_seg} for write zeroes
> commands.
> +The \field{data} used for discard, secure erase or write zeroes
> +commands consists of one or more segments. The maximum number of
> +segments is \field{max_discard_seg} for discard commands,
> +\field{max_secure_erase_seg} for secure erase commands and
> +\field{max_write_zeroes_seg} for write zeroes commands.
> Each segment is of form:
>
> \begin{lstlisting}
> @@ -4729,8 +4750,8 @@ \subsection{Device Operation}\label{sec:Device
> Types / Block Device / Device Ope and VIRTIO_BLK_T_OUT requests.
>
> The length of \field{data} MUST be a multiple of the size of struct -
> virtio_blk_discard_write_zeroes for VIRTIO_BLK_T_DISCARD and -
> VIRTIO_BLK_T_WRITE_ZEROES requests.
> +virtio_blk_discard_write_zeroes for VIRTIO_BLK_T_DISCARD,
> +VIRTIO_BLK_T_SECURE_ERASE and VIRTIO_BLK_T_WRITE_ZEROES requests.
>
> The length of \field{data} MUST be 20 bytes for VIRTIO_BLK_T_GET_ID requests.
>
> @@ -4738,6 +4759,10 @@ \subsection{Device Operation}\label{sec:Device
> Types / Block Device / Device Ope \field{max_discard_seg} struct
> virtio_blk_discard_write_zeroes segments in \field{data}.
>
> +VIRTIO_BLK_T_SECURE_ERASE requests MUST NOT contain more than
> +\field{max_secure_erase_seg} struct virtio_blk_discard_write_zeroes
> +segments in \field{data}.
> +
> VIRTIO_BLK_T_WRITE_ZEROES requests MUST NOT contain more than
> \field{max_write_zeroes_seg} struct virtio_blk_discard_write_zeroes segments
> in \field{data}.
> @@ -4764,7 +4789,7 @@ \subsection{Device Operation}\label{sec:Device
> Types / Block Device / Device Ope write any data.
>
> The device MUST set the \field{status} byte to VIRTIO_BLK_S_UNSUPP for -
> discard and write zeroes commands if any unknown flag is set.
> +discard, secure erase and write zeroes commands if any unknown flag is set.
> Furthermore, the device MUST set the \field{status} byte to
> VIRTIO_BLK_S_UNSUPP for discard commands if the \field{unmap} flag is set.
>
> --
> 2.25.1
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