Re: [PATCH v2 00/15] KVM: x86: Clean up kvm_<reg>_{read,write}() mess

[Yosry Ahmed]

On Thu, May 14, 2026 at 2:54 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> Add proper, explicit "raw" versions of kvm_<reg>_{read,write}(), along
> with "e" versions (for hardcoded 32-bit accesses), and convert the
> existing kvm_<reg>_{read,write}() APIs into mode-aware variants.
>
> This was prompted by commit 435741a4e766 ("KVM: SVM: Properly check RAX
> on #GP intercept of SVM instructions"), where using kvm_rax_read() to
> get EAX/RAX would have (*very* surprisingly) been wrong as it's actually
> a "raw" variant that doesn't truncate accesses when the guest is in 32-bit
> mode.
>
> Aside from my dislike of inconsistent APIs, I really want to avoid carrying
> code that's subtly relying on using kvm_register_read(...) when accessing a
> hardcoded register.
>
> Fix a handful of minor warts along the way.
>
> Oh, and introduce regs.{c,h}, which just a "minor" addendum.  Yosry pointed
> out that moving _more_ code into x86.h was rather gross (especially since the
> code split was super arbitrary), and it turns out that create regs.{c,h} isn't
> all that hard.  In the future, I think we can also add msr.{c,h}, so I very
> deliberately didn't include that functionality in regs.{c,h}.
>
> v2:
>  - Collect tags. [Yosry, Kai
>  - Fix some truly egregious goofs. [Binbin]
>  - Rename kvm_cache_regs.h => regs.h, add regs.c. [Yosry, though he'll
>    probably yell at me for saying this was his suggestion :-) ]

This is kinda sorta the opposite of what I suggested, but sure :P