Re: [edk2-devel] 回复: [edk2-devel] [PATCH v2 03/13] OvmfPkg:PlatformCI: Support virtio-rng-pci

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

On Fri, May 17, 2024 at 09:27:53AM GMT, Ard Biesheuvel wrote:
> On Fri, 17 May 2024 at 05:27, Doug Flick via groups.io
> <dougflick=microsoft.com@groups.io> wrote:
> >
> > On ARM, we can actually do better than this: I have taken Doug's v2 and applied some changes on top to make it work with ArmVirtQemu.
> >
> > https://github.com/ardbiesheuvel/edk2/tree/doug-v2
> >
> > Ard, would you be comfortable with this patch series if I take the commits you're suggesting? I'm being asked to see what it would take to get these commits in for this release.
> 
> I won't object to that, but I'd like Gerd's take as well, given that a
> similar concern appears to apply to OVMF/x86 IIUC.

I think including RngDxe in OvmfPkg is not an option.  That would
be a silent regression on the random number quality delivered by
EFI_RNG_PROTOCOL because OvmfPkg uses BaseRngLibTimerLib.

Switching to BaseRngLib is an easy way out for physical platforms
with a sufficient recent processor.  OVMF can not assume the rdrand
instruction is available, so that is not possible.

So short-term (i.e. 2024-05 stable tag) the only option I see is
depending on virtio-rng.  Which is a regression too (network booting
without '-device virtio-rng-pci' breaks), but it is an obvious failure
with an easy fix.  Not an ideal solution, but much better than a
regression which can easily go unnoticed.

Longer term it probably makes sense to have a EFI_RNG_PROTOCOL driver
using the rdrand instruction and runtime detection whenever the
instruction is available or not.  Either by adapting RngDxe accordingly,
or by having an OVMF-specific driver handling the runtime detection.

take care,
  Gerd



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