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From: Sean Christopherson <seanjc@google.com>
To: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: Jim Mattson <jmattson@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	 Thomas Gleixner <tglx@kernel.org>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	 Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org,  "H. Peter Anvin" <hpa@zytor.com>,
	Shuah Khan <shuah@kernel.org>,
	kvm@vger.kernel.org,  linux-kernel@vger.kernel.org,
	linux-kselftest@vger.kernel.org
Subject: Re: [PATCH v3 3/8] KVM: x86: nSVM: Set vmcb02.g_pat correctly for nested NPT
Date: Fri, 6 Feb 2026 11:14:50 -0800	[thread overview]
Message-ID: <aYY9qhsOMv_M9Ray@google.com> (raw)
In-Reply-To: <0468715595718af34a8a3551663cffa79dd3ce2e@linux.dev>

On Fri, Feb 06, 2026, Yosry Ahmed wrote:
> February 6, 2026 at 10:23 AM, "Sean Christopherson" <seanjc@google.com> wrote:
> > >  if (svm->nested.vmcb12_gpa != svm->nested.last_vmcb12_gpa) {
> > >  new_vmcb12 = true;
> > >  @@ -656,6 +653,19 @@ static void nested_vmcb02_prepare_save(struct vcpu_svm *svm, struct vmcb *vmcb12
> > >  svm->nested.force_msr_bitmap_recalc = true;
> > >  }
> > >  
> > >  + if (npt_enabled) {
> > >  + if (nested_npt_enabled(svm)) {
> > >  + if (unlikely(new_vmcb12 ||
> > >  + vmcb_is_dirty(vmcb12, VMCB_NPT))) {
> > >  + vmcb02->save.g_pat = svm->nested.gpat;
> > >  + vmcb_mark_dirty(vmcb02, VMCB_NPT);
> > >  + }
> > >  + } else {
> > >  + vmcb02->save.g_pat = vcpu->arch.pat;
> > >  + vmcb_mark_dirty(vmcb02, VMCB_NPT);
> > >  + }
> > >  + }
> > > 
> > To reduce indentation, how about this? There's a consistency check for
> > nested_npt_enabled() vs. npt_enabled, so it's guaranteed to do the right thing.
> 
> You mean the one that goes away after this patch: https://lore.kernel.org/kvm/20260115011312.3675857-16-yosry.ahmed@linux.dev/?

Heh, still fine.  All that matters is that nested_npt_enabled() can't be %true
if npt_enabled is %false.

  reply	other threads:[~2026-02-06 19:14 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-02-05 21:43 [PATCH v3 0/8] KVM: x86: nSVM: Improve PAT virtualization Jim Mattson
2026-02-05 21:43 ` [PATCH v3 1/8] KVM: x86: nSVM: Clear VMCB_NPT clean bit when updating g_pat in L2 Jim Mattson
2026-02-09 16:05   ` Yosry Ahmed
2026-02-05 21:43 ` [PATCH v3 2/8] KVM: x86: nSVM: Cache and validate vmcb12 g_pat Jim Mattson
2026-02-06 18:19   ` Sean Christopherson
2026-02-06 18:23     ` Yosry Ahmed
2026-02-06 18:32       ` Jim Mattson
2026-02-06 19:12         ` Sean Christopherson
2026-02-06 19:15           ` Yosry Ahmed
2026-02-06 19:50             ` Sean Christopherson
2026-02-06 20:56           ` Jim Mattson
2026-02-06 23:07             ` Sean Christopherson
2026-02-05 21:43 ` [PATCH v3 3/8] KVM: x86: nSVM: Set vmcb02.g_pat correctly for nested NPT Jim Mattson
2026-02-06 18:23   ` Sean Christopherson
2026-02-06 18:29     ` Yosry Ahmed
2026-02-06 19:14       ` Sean Christopherson [this message]
2026-02-05 21:43 ` [PATCH v3 4/8] KVM: x86: nSVM: Redirect IA32_PAT accesses to either hPAT or gPAT Jim Mattson
2026-02-05 21:43 ` [PATCH v3 5/8] KVM: x86: nSVM: Save gPAT to vmcb12.g_pat on VMEXIT Jim Mattson
2026-02-05 21:43 ` [PATCH v3 6/8] KVM: x86: nSVM: Save/restore gPAT with KVM_{GET,SET}_NESTED_STATE Jim Mattson
2026-02-05 21:43 ` [PATCH v3 7/8] KVM: x86: nSVM: Handle restore of legacy nested state Jim Mattson
2026-02-06 19:17   ` Sean Christopherson
2026-02-06 22:38     ` Jim Mattson
2026-02-05 21:43 ` [PATCH v3 8/8] KVM: selftests: nSVM: Add svm_nested_pat test Jim Mattson

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