Re: [PATCH] KVM: SVM: correct the size of spec_ctrl field in VMCB save area

[Sean Christopherson <seanjc@google.com>]

On Mon, Jul 17, 2023, Tom Lendacky wrote:
> On 7/16/23 23:19, Manali Shukla wrote:
> > Correct the spec_ctrl field in the VMCB save area based on the AMD
> > Programmer's manual.
> > 
> > Originally, the spec_ctrl was listed as u32 with 4 bytes of reserved

Nit, either just "spec_ctrl" or "the spec_ctrl field", specific MSRs and fields
are essentially proper nouns when used as nouns and not adjectives.

> > area.  The AMD Programmer's Manual now lists the spec_ctrl as 8 bytes
> > in VMCB save area.
> > 
> > The Public Processor Programming reference for Genoa, shows SPEC_CTRL
> > as 64b register, but the AMD Programmer's Manual lists SPEC_CTRL as

Nit, write out 64-bit (and 32-bit) so that there's zero ambiguity (I paused for
a few seconds to make sure I was reading it correctly).  64b is perfectly valid,
but nowhere near as common in the kernel, e.g.

  $ git log | grep -E "\s64b\s" | wc -l
  160
  $ git log | grep -E "\s64-bit\s" | wc -l
  8334

> > 32b register. This discrepancy will be cleaned up in next revision of
> > the AMD Programmer's Manual.
> > 
> > Since remaining bits above bit 7 are reserved bits in SPEC_CTRL MSR
> > and thus, not being used, the spec_ctrl added as u32 in the VMCB save

Same comment about "the spec_ctrl" here.

> > area is currently not an issue.
> > 
> > Fixes: 3dd2775b74c9 ("KVM: SVM: Create a separate mapping for the SEV-ES save area")
> 
> The more appropriate Fixes: tag should the be commit that originally
> introduced the spec_ctrl field:
> 
> d00b99c514b3 ("KVM: SVM: Add support for Virtual SPEC_CTRL")
> 
> Although because of 3dd2775b74c9, backports to before that might take some
> manual work.

And

  Cc: stable@vger.kernel.org

to make sure this gets backported.

No need for a v2, I can fixup all the nits when applying.