linux-kernel - Re: [RFC PATCH 06/13] kvm: Add KVM_CAP_EXECONLY

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Date:   Fri, 4 Oct 2019 19:11:28 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "Christopherson, Sean J" <sean.j.christopherson@...el.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "luto@...nel.org" <luto@...nel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Hansen, Dave" <dave.hansen@...el.com>
CC:     "kristen@...ux.intel.com" <kristen@...ux.intel.com>,
        "Dock, Deneen T" <deneen.t.dock@...el.com>
Subject: Re: [RFC PATCH 06/13] kvm: Add KVM_CAP_EXECONLY_MEM

On Fri, 2019-10-04 at 09:24 +0200, Paolo Bonzini wrote:
> On 03/10/19 23:23, Rick Edgecombe wrote:
> > Add a KVM capability for the KVM_MEM_EXECONLY memslot type. This memslot
> > type is supported if the HW supports execute-only TDP.
> > 
> > Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
> > ---
> >  arch/x86/include/asm/kvm_host.h | 1 +
> >  arch/x86/kvm/svm.c              | 6 ++++++
> >  arch/x86/kvm/vmx/vmx.c          | 1 +
> >  arch/x86/kvm/x86.c              | 3 +++
> >  include/uapi/linux/kvm.h        | 1 +
> >  5 files changed, 12 insertions(+)
> > 
> > diff --git a/arch/x86/include/asm/kvm_host.h
> > b/arch/x86/include/asm/kvm_host.h
> > index 6d06c794d720..be3ff71e6227 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -1132,6 +1132,7 @@ struct kvm_x86_ops {
> >  	bool (*xsaves_supported)(void);
> >  	bool (*umip_emulated)(void);
> >  	bool (*pt_supported)(void);
> > +	bool (*tdp_xo_supported)(void);
> >  
> >  	int (*check_nested_events)(struct kvm_vcpu *vcpu, bool external_intr);
> >  	void (*request_immediate_exit)(struct kvm_vcpu *vcpu);
> > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> > index e0368076a1ef..f9f25f32e946 100644
> > --- a/arch/x86/kvm/svm.c
> > +++ b/arch/x86/kvm/svm.c
> > @@ -6005,6 +6005,11 @@ static bool svm_pt_supported(void)
> >  	return false;
> >  }
> >  
> > +static bool svm_xo_supported(void)
> > +{
> > +	return false;
> > +}
> > +
> >  static bool svm_has_wbinvd_exit(void)
> >  {
> >  	return true;
> > @@ -7293,6 +7298,7 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init
> > = {
> >  	.xsaves_supported = svm_xsaves_supported,
> >  	.umip_emulated = svm_umip_emulated,
> >  	.pt_supported = svm_pt_supported,
> > +	.tdp_xo_supported = svm_xo_supported,
> >  
> >  	.set_supported_cpuid = svm_set_supported_cpuid,
> >  
> > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> > index a30dbab8a2d4..7e7260c715f2 100644
> > --- a/arch/x86/kvm/vmx/vmx.c
> > +++ b/arch/x86/kvm/vmx/vmx.c
> > @@ -7767,6 +7767,7 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init
> > = {
> >  	.xsaves_supported = vmx_xsaves_supported,
> >  	.umip_emulated = vmx_umip_emulated,
> >  	.pt_supported = vmx_pt_supported,
> > +	.tdp_xo_supported = cpu_has_vmx_ept_execute_only,
> >  
> >  	.request_immediate_exit = vmx_request_immediate_exit,
> >  
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 2e321d788672..810cfdb1a315 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -3183,6 +3183,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long
> > ext)
> >  		r = kvm_x86_ops->get_nested_state ?
> >  			kvm_x86_ops->get_nested_state(NULL, NULL, 0) : 0;
> >  		break;
> > +	case KVM_CAP_EXECONLY_MEM:
> > +		r = kvm_x86_ops->tdp_xo_supported();
> > +		break;
> >  	default:
> >  		break;
> >  	}
> > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> > index ede487b7b216..7778a1f03b78 100644
> > --- a/include/uapi/linux/kvm.h
> > +++ b/include/uapi/linux/kvm.h
> > @@ -997,6 +997,7 @@ struct kvm_ppc_resize_hpt {
> >  #define KVM_CAP_ARM_PTRAUTH_ADDRESS 171
> >  #define KVM_CAP_ARM_PTRAUTH_GENERIC 172
> >  #define KVM_CAP_PMU_EVENT_FILTER 173
> > +#define KVM_CAP_EXECONLY_MEM 174
> >  
> >  #ifdef KVM_CAP_IRQ_ROUTING
> >  
> > 
> 
> This is not needed, execution only can be a CPUID bit in the hypervisor
> range (see Documentation/virt/kvm/cpuid.txt).  Userspace can use
> KVM_GET_SUPPORTED_CPUID to check whether the host supports it.
> 
Oh yea. I didn't see this. Definitely seems better.

Thanks,

Rick