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Subject: [PATCH v2 3/3] shared memory: Define mmio registers
From: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Define an MMIO interface to enumerate and map shared memory regions. Note: This hasn't been implemented. Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com> --- content.tex | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/content.tex b/content.tex index 9838208..c3070bd 100644 --- a/content.tex +++ b/content.tex @@ -1726,6 +1726,28 @@ All register values are organized as Little Endian. selected by writing to \field{QueueSel}. } \hline + \mmioreg{SHMId}{Shared memory id}{0x0ac}{W}{% + Writing to this register selects the shared memory region \ref{sec:Basic Facilities of a Virtio Device / Shared Memory Regions} + following operations on \field{SHMLenLow}, \field{SHMLenHigh}, + \field{SHMBaseLow} and \field{SHMBaseHigh} apply to. + } + \hline + \mmiodreg{SHMLenLow}{SHMLenHigh}{Shared memory region 64 bit long length}{0x0b0}{0x0xb4}{R}{% + These registers return the length of the shared memory + region, as defined by the device for the region selected by + the \field{SHMId} register. Reading from a non-existent + region (i.e. where the ID written to \field{SHMId} is unused) + results in a length of -1. + } + \hline + \mmiodreg{SHMBaseLow}{SHMBaseHigh}{Shared memory region 64 bit long physical address}{0x0b8}{0x0xbc}{W}{% + The driver writes these registers to indicate where it wishes + the device to map the shared memory region currently + selected. The driver shall write \field{SHMBaseLow} first + and then \field{SHMBaseHigh}. To avoid multiple remappings, the device shall not change + the mapping until it sees the write to \field{SHMBaseHigh}. + } + \hline \mmioreg{ConfigGeneration}{Configuration atomicity value}{0x0fc}{R}{ Reading from this register returns a value describing a version of the device-specific configuration space (see \field{Config}). The driver can then access the configuration space and, when finished, read \field{ConfigGeneration} again. @@ -1761,6 +1783,9 @@ driver seeing an inconsistent configuration state. The device MUST NOT access virtual queue contents when \field{QueueReady} is zero (0x0). +The device MUST NOT respond to SHM Base writes for none-existent +shared memory regions. + \drivernormative{\subsubsection}{MMIO Device Register Layout}{Virtio Transport Options / Virtio Over MMIO / MMIO Device Register Layout} The driver MUST NOT access memory locations not described in the table \ref{tab:Virtio Trasport Options / Virtio Over MMIO / MMIO Device Register Layout} @@ -1815,6 +1840,13 @@ If both values are valid, it MUST read \field{DeviceID} and if its value is zero (0x0) MUST abort initialization and MUST NOT access any other register. +Devices expecting shared memory regions MUST enumerate the +regions by selecting each region in tern and checking that the +length is not -1. + +Devices not expecting shared memory MUST NOT use the shared +memory registers. + Further initialization MUST follow the procedure described in \ref{sec:General Initialization And Device Operation / Device Initialization}~\nameref{sec:General Initialization And Device Operation / Device Initialization}. -- 2.20.1
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