Re: [PATCH 1/2] KVM: VMX: Drop obsolete branch hint prefixes from inline asm

[Andrew Cooper]

On 11/02/2026 4:17 pm, Sean Christopherson wrote:
> On Wed, Feb 11, 2026, Andrew Cooper wrote:
>> On 11/02/2026 3:44 pm, Sean Christopherson wrote:
>>> On Wed, Feb 11, 2026, Andrew Cooper wrote:
>> This change is almost certainly marginal at best.  It's not as if
>> VMREAD/VMWRITE lead to good code gen even at the best of times.
> Yeah, but adding in them in the first place was even more marginal (I added the
> hints as much for documentation purposes as anything else).  Absent proof that
> having the hints is a net positive, I'm inclined to trust the compiler folks on
> what is/isn't optimal, and drop them.

Branch mispredicts in the P4 could easily eat up 150 cycles before the
frontend got it's act together.

However, optimising VMREAD/VMWRITE and not the whole kernel seems
somewhat futile.

~Andrew