Re: [PATCH] x86/sev: Remove bogus virtual address check

[Borislav Petkov]

On Wed, Apr 01, 2026 at 10:12:56AM +0200, Ard Biesheuvel wrote:
> 
> On Wed, 1 Apr 2026, at 10:03, Alexey Kardashevskiy wrote:
> > On 1/4/26 18:29, Ard Biesheuvel wrote:
> >> On Tue, 31 Mar 2026, at 23:30, Alexey Kardashevskiy wrote:
> >>> On 1/4/26 00:21, Ard Biesheuvel wrote:
> >>>> (add Eric back to cc)
> >>>>
> >>>> Please keep Eric on cc - I added him for a reason, thanks.
> >>>>
> >>>>
> >>>> On Tue, 31 Mar 2026, at 15:18, Ard Biesheuvel wrote:
> >>>>> On Tue, 31 Mar 2026, at 15:16, Borislav Petkov wrote:
> >>>>>> On Fri, Oct 10, 2025 at 05:10:37PM +0200, Ard Biesheuvel wrote:
> >>>>>>> From: Ard Biesheuvel <ardb@xxxxxxxxxx>
> >>>>>>>
> >>>>>>> The AES-GCM crypto library operates strictly on virtual addresses,
> >>>>>>> and never performs any H/W offload, and so calling
> >>>>>>> virt_addr_valid() is not needed.
> >>>>>>>
> >> ...
> >>>>>>
> >>>>>> This came from:
> >>>>>>
> >>>>>>     7ffeb2fc2670 ("x86/sev: Document requirement for linear mapping
> >>>>>>     of guest request buffers")
> >>>
> >>> Nah, this is because of db10cb9b574675402b virt: sevguest: Fix passing
> >>> a stack buffer as a scatterlist target
> >>>
> >> 
> >> Is that change still needed after
> >> 
> >>    f3476bc77057 ("virt: sev-guest: Use AES GCM crypto library")
> >
> > huh. You're right, looks like it is not, I missed that.
> >
> >> If not, should we revert db10cb9b574675402b too?
> >
> > Nah, we do not want these structures on stack anyway (they might get 
> > too big in the future).
> >
> >> Using the crypto API for simple operations where the algorithm is known
> >> at build time was always a mistake. But moving stack allocations to the
> >> heap just to placate a clunky API that can only be used meaningfully in
> >> an asynchronous manner in the first place is just pointless.
> >
> > True.
> >
> > Reviewed-by: Alexey Kardashevskiy <aik@xxxxxxx>
> > Tested-by: Alexey Kardashevskiy <aik@xxxxxxx>
> >
> > or should I reply with these to the original mail?
> >
> 
> Thanks. I think it should be fine like this.

And now let's invite the folks from

db10cb9b5746 ("virt: sevguest: Fix passing a stack buffer as a scatterlist target")

to the party so that the circle is complete. :-)

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette