Re: [edk2-devel] [PATCH v3 1/4] OvmfPkg/Sec: Setup MTRR early in the boot process.

["Gerd Hoffmann" <kraxel@redhat.com>]

On Thu, Feb 01, 2024 at 06:10:26AM +0000, Sun, Yi Y wrote:
> Hi, all,
> 
> Per our test, this issue only happens when the mdev/vdev is assigned
> to VM. But PF(physical function)/VF(virtual function) assignment is
> good. Per Jiaqing's investigation, it is because that the mdev/vdev
> passthrough flow is different with PF/VF. For vdev/mdev passthrough to
> VM, the enforce_cache_coherency was enabled after device bound to
> iommufd. But it doesn't update the kvm coherency state after that.
> This makes the memory type be UNCACHABLE which causes the reading is
> very slow.
> 
> So, what is your opinion to fix it? Which side to fix it is better,
> ovmf or vfio? Thanks!

Both?  For OVMF it surely makes sense to properly setup MTRRs.  And if
the cache coherency behavior of vfio is not correct that should be fixed
too of course.

take care,
  Gerd



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