diff options
| author | mstsirkin <mstsirkin@0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652> | 2015-04-22 08:26:11 +0000 |
|---|---|---|
| committer | mstsirkin <mstsirkin@0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652> | 2015-04-22 08:26:11 +0000 |
| commit | fdc047cb06529edebed75a185b2bab7383161470 (patch) | |
| tree | 8b56dc6bed5398a2ef05c7fd81c7ee483b9545f4 /content.tex | |
| parent | a75a70b428f33cf2b684f09a4b0dcc7985726b02 (diff) | |
pci: missing documentation for dealing with 64 bit config fields
pci spec says what width access to use for 32, 16 and 8
bit fields, but does not explicitly say what to do for
32 bit fields. As we have text that says driver must
treat 64 bit accesses as non-atomic, this seems
to imply driver should always do two 32 bit wide accesses.
Let's make this an explicit requirement, and require
devices to support this.
VIRTIO-139
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@508 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
Diffstat (limited to 'content.tex')
| -rw-r--r-- | content.tex | 19 |
1 files changed, 14 insertions, 5 deletions
diff --git a/content.tex b/content.tex index 48d735d..95ae23e 100644 --- a/content.tex +++ b/content.tex @@ -1083,14 +1083,23 @@ Structure PCI Capabilities. Fields of different sizes are present in the device configuration regions. -All 32-bit and 16-bit fields are little-endian. +All 64-bit, 32-bit and 16-bit fields are little-endian. +64-bit fields are to be treated as two 32-bit fields, +with low 32 bit part followed by the high 32 bit part. \drivernormative{\subsubsection}{PCI Device Layout}{Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout} -The driver -MUST access each field using the ``natural'' access method, i.e. -32-bit accesses for 32-bit fields, 16-bit accesses for 16-bit -fields and 8-bit accesses for 8-bit fields. +For device configuration access, the driver MUST use 8-bit wide +accesses for 8-bit wide fields, 16-bit wide and aligned accesses +for 16-bit wide fields and 32-bit wide and aligned accesses for +32-bit and 64-bit wide fields. For 64-bit fields, the driver MAY +access each of the high and low 32-bit parts of the field +independently. + +\devicenormative{\subsubsection}{PCI Device Layout}{Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout} + +For 64-bit device configuration fields, the device MUST allow driver +independent access to high and low 32-bit parts of the field. \subsection{Virtio Structure PCI Capabilities}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / Virtio Structure PCI Capabilities} |