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

[Ard Biesheuvel]

[ replying a second time since the first one seems to have evaporated -
apologies if you are seeing two replies that look vaguely but not
exactly the same]

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")

If not, should we revert db10cb9b574675402b too?

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.