Re: [PATCH v2 08/15] KVM: x86: Add Arch LBR MSRs to msrs_to_save_all list

[Yang, Weijiang]

On 1/28/2023 5:43 AM, Sean Christopherson wrote:
> On Thu, Nov 24, 2022, Yang Weijiang wrote:
> > Arch LBR MSR_ARCH_LBR_DEPTH and MSR_ARCH_LBR_CTL are queried by
> > userspace application before it wants to {save|restore} the Arch LBR
> > data. Other LBR related data MSRs are omitted here intentionally due
> > to lengthy list(32*3). Userspace can still use KVM_{GET|SET}_MSRS to
> > access them if necessary.
> Absolutely not.  "there are a lot of them" isn't sufficient justification.  If
> the MSRs need to be migrated, then KVM needs to report them.  If the expectation
> is that XSAVES will handle them, then KVM needs to take a dependency on XSAVES
> when enabling arch LBRs.

OK, will add the full MSR list.