Re: [PATCH v8] vfio/pci: Add OpRegion 2.0+ Extended VBT support.

[Alex Williamson <alex.williamson@redhat.com>]

On Tue, 12 Oct 2021 20:48:55 +0800
Colin Xu <colin.xu@gmail.com> wrote:

> From: Colin Xu <colin.xu@intel.com>
> 
> Due to historical reason, some legacy shipped system doesn't follow
> OpRegion 2.1 spec but still stick to OpRegion 2.0, in which the extended
> VBT is not contiguous after OpRegion in physical address, but any
> location pointed by RVDA via absolute address. Also although current
> OpRegion 2.1+ systems appears that the extended VBT follows OpRegion,
> RVDA is the relative address to OpRegion head, the extended VBT location
> may change to non-contiguous to OpRegion. In both cases, it's impossible
> to map a contiguous range to hold both OpRegion and the extended VBT and
> expose via one vfio region.
> 
> The only difference between OpRegion 2.0 and 2.1 is where extended
> VBT is stored: For 2.0, RVDA is the absolute address of extended VBT
> while for 2.1, RVDA is the relative address of extended VBT to OpRegion
> baes, and there is no other difference between OpRegion 2.0 and 2.1.
> To support the non-contiguous region case as described, the updated read
> op will patch OpRegion version and RVDA on-the-fly accordingly. So that
> from vfio igd OpRegion view, only 2.1+ with contiguous extended VBT
> after OpRegion is exposed, regardless the underneath host OpRegion is
> 2.0 or 2.1+. The mechanism makes it possible to support legacy OpRegion
> 2.0 extended VBT systems with on the market, and support OpRegion 2.1+
> where the extended VBT isn't contiguous after OpRegion.
> 
> V2:
> Validate RVDA for 2.1+ before increasing total size. (Alex)
> 
> V3: (Alex)
> Split read and write ops.
> On-the-fly modify OpRegion version and RVDA.
> Fix sparse error on assign value to casted pointer.
> 
> V4: (Alex)
> No need support write op.
> Direct copy to user buffer with several shift instead of shadow.
> Copy helper to copy to user buffer and shift offset.
> 
> V5: (Alex)
> Simplify copy help to only cover common shift case.
> Don't cache patched version and rvda. Patch on copy if necessary.
> 
> V6:
> Fix comment typo and max line width.
> 
> V7:
> Keep bytes to copy/remain as size_t.
> Proper shift byte address on copy source.
> Rebase to linux-next.
> 
> V8:
> Replace min() with min_t() to avoid type cast.
> Wrap long lines.
> 
> Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
> Cc: Hang Yuan <hang.yuan@linux.intel.com>
> Cc: Swee Yee Fonn <swee.yee.fonn@intel.com>
> Cc: Fred Gao <fred.gao@intel.com>
> Signed-off-by: Colin Xu <colin.xu@intel.com>
> ---
>  drivers/vfio/pci/vfio_pci_igd.c | 234 ++++++++++++++++++++++++--------
>  1 file changed, 175 insertions(+), 59 deletions(-)

Looks good, applied to vfio next branch for v5.16.  Thanks,

Alex