linux-kernel - Re: [PATCH 3/6] KVM: nSVM: Introduce svm_copy_nonvmloadsave

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Date:   Wed, 07 Jul 2021 13:29:32 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Cathy Avery <cavery@...hat.com>,
        Emanuele Giuseppe Esposito <eesposit@...hat.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Michael Roth <mdroth@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] KVM: nSVM: Introduce svm_copy_nonvmloadsave_state()

On Mon, 2021-07-05 at 14:08 +0200, Paolo Bonzini wrote:
> On 28/06/21 12:44, Vitaly Kuznetsov wrote:
> > Separate the code setting non-VMLOAD-VMSAVE state from
> > svm_set_nested_state() into its own function. This is going to be
> > re-used from svm_enter_smm()/svm_leave_smm().
> > 
> > Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> > ---
> >   arch/x86/kvm/svm/nested.c | 36 +++++++++++++++++++++---------------
> >   arch/x86/kvm/svm/svm.h    |  2 ++
> >   2 files changed, 23 insertions(+), 15 deletions(-)
> > 
> > diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> > index 1c6b0698b52e..a1dec2c40181 100644
> > --- a/arch/x86/kvm/svm/nested.c
> > +++ b/arch/x86/kvm/svm/nested.c
> > @@ -697,6 +697,26 @@ int nested_svm_vmrun(struct kvm_vcpu *vcpu)
> >   	return ret;
> >   }
> >   
> > +void svm_copy_nonvmloadsave_state(struct vmcb_save_area *from_save,
> > +				  struct vmcb_save_area *to_save)
> 
> Probably best to name this svm_copy_vmrun_state and perhaps (as a 
> cleanup) change nested_svm_vmloadsave to svm_copy_vmloadsave_state.

I agree with that. I would also add a comment to both 
svm_copy_vmloadsave_state and svm_copy_vmrun_state stating what they
are doing, like "this function copies state save area fields which
are used by vmrun"

Best regards,
	Maxim Levitsky


> 
> Paolo
> 
> > +{
> > +	to_save->es = from_save->es;
> > +	to_save->cs = from_save->cs;
> > +	to_save->ss = from_save->ss;
> > +	to_save->ds = from_save->ds;
> > +	to_save->gdtr = from_save->gdtr;
> > +	to_save->idtr = from_save->idtr;
> > +	to_save->rflags = from_save->rflags | X86_EFLAGS_FIXED;
> > +	to_save->efer = from_save->efer;
> > +	to_save->cr0 = from_save->cr0;
> > +	to_save->cr3 = from_save->cr3;
> > +	to_save->cr4 = from_save->cr4;
> > +	to_save->rax = from_save->rax;
> > +	to_save->rsp = from_save->rsp;
> > +	to_save->rip = from_save->rip;
> > +	to_save->cpl = 0;
> > +}
> > +
> >   void nested_svm_vmloadsave(struct vmcb *from_vmcb, struct vmcb *to_vmcb)
> >   {
> >   	to_vmcb->save.fs = from_vmcb->save.fs;
> > @@ -1360,21 +1380,7 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
> >   
> >   	svm->nested.vmcb12_gpa = kvm_state->hdr.svm.vmcb_pa;
> >   
> > -	svm->vmcb01.ptr->save.es = save->es;
> > -	svm->vmcb01.ptr->save.cs = save->cs;
> > -	svm->vmcb01.ptr->save.ss = save->ss;
> > -	svm->vmcb01.ptr->save.ds = save->ds;
> > -	svm->vmcb01.ptr->save.gdtr = save->gdtr;
> > -	svm->vmcb01.ptr->save.idtr = save->idtr;
> > -	svm->vmcb01.ptr->save.rflags = save->rflags | X86_EFLAGS_FIXED;
> > -	svm->vmcb01.ptr->save.efer = save->efer;
> > -	svm->vmcb01.ptr->save.cr0 = save->cr0;
> > -	svm->vmcb01.ptr->save.cr3 = save->cr3;
> > -	svm->vmcb01.ptr->save.cr4 = save->cr4;
> > -	svm->vmcb01.ptr->save.rax = save->rax;
> > -	svm->vmcb01.ptr->save.rsp = save->rsp;
> > -	svm->vmcb01.ptr->save.rip = save->rip;
> > -	svm->vmcb01.ptr->save.cpl = 0;
> > +	svm_copy_nonvmloadsave_state(save, &svm->vmcb01.ptr->save);
> >   
> >   	nested_load_control_from_vmcb12(svm, ctl);
> >   
> > diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> > index f89b623bb591..ff2dac2b23b6 100644
> > --- a/arch/x86/kvm/svm/svm.h
> > +++ b/arch/x86/kvm/svm/svm.h
> > @@ -463,6 +463,8 @@ void svm_leave_nested(struct vcpu_svm *svm);
> >   void svm_free_nested(struct vcpu_svm *svm);
> >   int svm_allocate_nested(struct vcpu_svm *svm);
> >   int nested_svm_vmrun(struct kvm_vcpu *vcpu);
> > +void svm_copy_nonvmloadsave_state(struct vmcb_save_area *from_save,
> > +				  struct vmcb_save_area *to_save);
> >   void nested_svm_vmloadsave(struct vmcb *from_vmcb, struct vmcb *to_vmcb);
> >   int nested_svm_vmexit(struct vcpu_svm *svm);
> >   
> >