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Diffstat (limited to 'content.tex')
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1 files changed, 30 insertions, 0 deletions
diff --git a/content.tex b/content.tex index 1476b0e..ee0d7c9 100644 --- a/content.tex +++ b/content.tex @@ -1736,6 +1736,33 @@ All register values are organized as Little Endian. selected by writing to \field{QueueSel}. } \hline + \mmioreg{SHMSel}{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 in bytes, as defined by the device for the region selected by + the \field{SHMSel} register. The lower 32 bits of the length + are read from \field{SHMLenLow} and the higher 32 bits from + \field{SHMLenHigh}. Reading from a non-existent + region (i.e. where the ID written to \field{SHMSel} is unused) + results in a length of -1. + } + \hline + \mmiodreg{SHMBaseLow}{SHMBaseHigh}{Shared memory region 64 bit long physical address}{0x0b8}{0x0xbc}{R}{% + The driver reads these registers to discover the base address + of the region in physical address space. This address is + chosen by the device (or other part of the VMM). + The lower 32 bits of the address are read from \field{SHMBaseLow} + with the higher 32 bits from \field{SHMBaseHigh}. Reading + from a non-existent region (i.e. where the ID written to + \field{SHMSel} is unused) results in a base address of + 0xffffffffffffffff. + } + \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. @@ -1825,6 +1852,9 @@ 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. +Drivers 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}. |