Re: [PATCH v2] KVM: x86: Remove AMX-TF32 enumeration

[Sean Christopherson <seanjc@google.com>]

On Thu, Jul 23, 2026, Chang S. Bae wrote:
> On 7/23/2026 11:04 AM, Sean Christopherson wrote:
> > 
> > I'm not convinced that yanking out support is the right move.  By publishing the
> > feature, for several years, Intel pretty much burned that CPUID bit.  E.g. it's
> > not impossible that someone other than Intel has implemented TF32 instructions.
> > 
> > The opcodes are fair game in the future, because their use can be qualified and
> > guarded, but the same doesn't hold true for enumeration.  E.g. similar to how
> > MPX got ripped out and its XSTATE assets got reused for APX, but the CPUID feature
> > enumeration is forever reserved for MPX (I hope).
> > 
> > If the argument is that "Intel Architecture Instruction Set Extensions and Future
> > Features" isn't binding documentation, i.e. that Intel can do take backs until a
> > feature is documented in the SDM, then I honestly don't see any option but to
> > refuse to accept new features until they land in the SDM.  Which I don't think
> > any of us want.
> One distinction I could think of is whether a feature ever ships in
> implementations. If a feature is actually implemented and is later
> deprecated or removed, then I agree the bit should remain reserved. That
> appears quite clear.

Per Christian, who's mail client apparently doesn't use In-Reply-To and breaks
threading for me and lore, TF32 made it into a shipped product[*].

So "officially", NAK.

[*] https://lore.kernel.org/all/CAKSQd8V%3DwfVrUxeU%2BfDRgKJBLdiyCkkY2SRY%2BOoRBNE68LFnCg@mail.gmail.com