linux-kernel - Re: [PATCH] KVM: x86: Unconditionally call x86 ops that are always implemented

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Date:   Fri, 2 Aug 2019 15:48:42 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Krish Sadhukhan <krish.sadhukhan@...cle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: x86: Unconditionally call x86 ops that are always
 implemented

On Thu, Aug 01, 2019 at 02:42:07PM -0700, Sean Christopherson wrote:
> On Thu, Aug 01, 2019 at 02:39:38PM -0700, Krish Sadhukhan wrote:
> > 
> > 
> > On 08/01/2019 09:46 AM, Sean Christopherson wrote:
> > >Remove two stale checks for non-NULL ops now that they're implemented by
> > >both VMX and SVM.
> > >
> > >Fixes: 74f169090b6f ("kvm/svm: Setup MCG_CAP on AMD properly")
> > >Fixes: b31c114b82b2 ("KVM: X86: Provide a capability to disable PAUSE intercepts")
> > >Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> > >---
> > >  arch/x86/kvm/x86.c | 8 ++------
> > >  1 file changed, 2 insertions(+), 6 deletions(-)
> > >
> > >diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > >index 01e18caac825..2c25a19d436f 100644
> > >--- a/arch/x86/kvm/x86.c
> > >+++ b/arch/x86/kvm/x86.c
> > >@@ -3506,8 +3506,7 @@ static int kvm_vcpu_ioctl_x86_setup_mce(struct kvm_vcpu *vcpu,
> > >  	for (bank = 0; bank < bank_num; bank++)
> > >  		vcpu->arch.mce_banks[bank*4] = ~(u64)0;
> > >-	if (kvm_x86_ops->setup_mce)
> > >-		kvm_x86_ops->setup_mce(vcpu);
> > >+	kvm_x86_ops->setup_mce(vcpu);
> > >  out:
> > >  	return r;
> > >  }
> > >@@ -9313,10 +9312,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> > >  	kvm_page_track_init(kvm);
> > >  	kvm_mmu_init_vm(kvm);
> > >-	if (kvm_x86_ops->vm_init)
> > >-		return kvm_x86_ops->vm_init(kvm);
> > >-
> > >-	return 0;
> > >+	return kvm_x86_ops->vm_init(kvm);
> > >  }
> > >  static void kvm_unload_vcpu_mmu(struct kvm_vcpu *vcpu)
> > 
> > The following two ops are also implemented by both VMX and SVM:
> > 
> >         update_cr8_intercept
> >         update_pi_irte
> 
> Drat, I didn't think to grep for !kvm_x86_ops.  I'll spin a v2.  Thanks!

Ah, but update_cr8_intercept is zapped by VMX if hardware doesn't support
the TPR shadow.

P.S. I meant to send this before posting v2, but I got distracted...