virtio — archive

[Michael S. Tsirkin]

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> --- conformance.tex 1 + content.tex 19 ++++++++++++++ ----- 2 files changed, 15 insertions(+), 5 deletions(-) diff --git a/conformance.tex b/conformance.tex index 350d2d0..0f601d7 100644 --- a/conformance.tex +++ b/conformance.tex @@ -155,6 +155,7 @@ A PCI device MUST conform to the following normative statements: egin{itemize} item ef{devicenormative:Virtio Transport Options / Virtio Over PCI Bus} item ef{devicenormative:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Discovery} +item ef{devicenormative:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout} item ef{devicenormative:Virtio Transport Options / Virtio Over PCI Bus / Virtio Structure PCI Capabilities} item ef{devicenormative:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Common configuration structure layout} item ef{devicenormative:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Notification capability} diff --git a/content.tex b/content.tex index d66785a..fd3fd17 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} -- MST