Re: [PATCH 0/2] KVM: nSVM: Expose DecodeAssists to L1

[Jim Mattson]

On Mon, Jun 29, 2026 at 5:57 AM Tina Zhang <zhang_wei@xxxxxxxxxxxxxx> wrote:
>
> The SVM DecodeAssists feature is reported in CPUID
> Fn8000_000A_EDX[7].  When available, hardware provides the length and bytes
> of the intercepted instruction in the VMCB, allowing a hypervisor to consume
> the decode information directly instead of re-decoding the instruction in
> software on relevant VM-Exit paths.

DecodeAssists actually comprises four components:
* GPR number in EXITINFO1 for MOV-CR and MOV-DR VM-exits
* Software interrupt number in EXITINFO1 for INTn VM-exits
* Linear address in EXITINFO1 for INVLPG[A] VM-exits
* Guest instruction bytes and length in the VMCB for #NPF and #PF VM-exits

You only partially address the last component.