RE: [PATCH v4] KVM: x86/xen: Update Xen CPUID Leaf 4 (tsc info) sub-leaves, if present

[Durrant, Paul]

> -----Original Message-----
> From: Sean Christopherson <seanjc@xxxxxxxxxx>
> Sent: 27 June 2022 16:19
> To: Durrant, Paul <pdurrant@xxxxxxxxxxxx>
> Cc: x86@xxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; David Woodhouse
> <dwmw2@xxxxxxxxxxxxx>; Paolo Bonzini <pbonzini@xxxxxxxxxx>; Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>;
> Wanpeng Li <wanpengli@xxxxxxxxxxx>; Jim Mattson <jmattson@xxxxxxxxxx>; Joerg Roedel <joro@xxxxxxxxxx>;
> Thomas Gleixner <tglx@xxxxxxxxxxxxx>; Ingo Molnar <mingo@xxxxxxxxxx>; Borislav Petkov <bp@xxxxxxxxx>;
> Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>; H. Peter Anvin <hpa@xxxxxxxxx>
> Subject: RE: [EXTERNAL][PATCH v4] KVM: x86/xen: Update Xen CPUID Leaf 4 (tsc info) sub-leaves, if
> present
> 
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> 
> On Wed, Jun 22, 2022, Paul Durrant wrote:
> > The scaling information in subleaf 1 should match the values set by KVM in
> > the 'vcpu_info' sub-structure 'time_info' (a.k.a. pvclock_vcpu_time_info)
> > which is shared with the guest, but is not directly available to the VMM.
> > The offset values are not set since a TSC offset is already applied.
> > The TSC frequency should also be set in sub-leaf 2.
> >
> > Cache pointers to the sub-leaves when CPUID is updated by the VMM and
> > populate the relevant information prior to entering the guest.
> 
> All of my comments about the code still apply.
> 
> https://lore.kernel.org/all/YrMqtHzNSean+qkh@xxxxxxxxxx
> 

Apologies. Not sure how I missed them; I'll send a response shortly.

> > Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
> > ---
> > Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
> 
> Cc: can go in the changelog, it's helpful info to carry with the commit as it
> documents who was made aware of the patch, e.g. show who may have had a cance to
> object/review.
> 
> >
> > v2:
> >  - Make sure sub-leaf pointers are NULLed if the time leaf is removed
> >
> > v3:
> >  - Add leaf limit check in kvm_xen_set_cpuid()
> >
> > v4:
> >  - Update commit comment
> 
> Please start with the most recent verison and work backardwards, that way reviewers
> can quickly see the delta for _this_ version.  I.e.
> 
> 
> v4:
> 
> v3:
> 
> v2:
> 
> v1:

Ok.

  Paul