Re: [RFC PATCH kernel 2/2] KVM: SEV: PreventHostIBS enablement for SEV-ES and SNP guest

[Nikunj A. Dadhania]

On 06/02/23 11:35, Manali Shukla wrote:
> Currently, the hypervisor is able to inspect instruction based samples
> from a guest and gather execution information. SEV-ES and SNP guests
> can disallow the use of instruction based sampling by hypervisor by
> enabling the PreventHostIBS feature for the guest.  (More information
> in Section 15.36.17 APM Volume 2)
> 
> The MSR_AMD64_IBSFETCHCTL[IbsFetchEn] and MSR_AMD64_IBSOPCTL[IbsOpEn]
> bits need to be disabled before VMRUN is called when PreventHostIBS
> feature is enabled. If either of these bits are not 0, VMRUN will fail
> with VMEXIT_INVALID error code.
> 
> Because of an IBS race condition when disabling IBS, KVM needs to
> indicate when it is in a PreventHostIBS window. Activate the window
> based on whether IBS is currently active or inactive.
> 
> Signed-off-by: Manali Shukla <manali.shukla@xxxxxxx>

Looks good.

Reviewed-by: Nikunj A Dadhania <nikunj@xxxxxxx>