linux-kernel - Re: [PATCH v2 11/13] KVM: nSVM: Simplify nested_svm

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Message-ID: <aThz5p655rk8D1KS@google.com>
Date: Tue, 9 Dec 2025 11:09:26 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Yosry Ahmed <yosry.ahmed@...ux.dev>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Jim Mattson <jmattson@...gle.com>, kvm@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 11/13] KVM: nSVM: Simplify nested_svm_vmrun()

On Tue, Dec 09, 2025, Yosry Ahmed wrote:
> On Tue, Dec 09, 2025 at 08:11:41AM -0800, Sean Christopherson wrote:
> > On Mon, Nov 10, 2025, Yosry Ahmed wrote:
> > > Call nested_svm_merge_msrpm() from enter_svm_guest_mode() if called from
> > > the VMRUN path, instead of making the call in nested_svm_vmrun(). This
> > > simplifies the flow of nested_svm_vmrun() and removes all jumps to
> > > cleanup labels.
> > > 
> > > Signed-off-by: Yosry Ahmed <yosry.ahmed@...ux.dev>
> > > ---
> > >  arch/x86/kvm/svm/nested.c | 28 +++++++++++++---------------
> > >  1 file changed, 13 insertions(+), 15 deletions(-)
> > > 
> > > diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> > > index a48668c36a191..89830380cebc5 100644
> > > --- a/arch/x86/kvm/svm/nested.c
> > > +++ b/arch/x86/kvm/svm/nested.c
> > > @@ -1020,6 +1020,9 @@ int enter_svm_guest_mode(struct kvm_vcpu *vcpu, u64 vmcb12_gpa, bool from_vmrun)
> > >  
> > >  	nested_svm_hv_update_vm_vp_ids(vcpu);
> > >  
> > > +	if (from_vmrun && !nested_svm_merge_msrpm(vcpu))
> > 
> > This is silly, just do:
> 
> Ack. Any objections to just dropping from_vmrun and moving
> kvm_make_request(KVM_REQ_GET_NESTED_STATE_PAGES) to svm_leave_smm()? I
> like the consistency of completely relying on from_vmrun or not at all

Zero objections.  When I was initially going through this, I actually thought you
were _adding_ the flag and was going to yell at you :-)