Commit 01b4f510 authored by Oliver Upton's avatar Oliver Upton Committed by Paolo Bonzini
Browse files

kvm: x86: ensure pv_cpuid.features is initialized when enabling cap 



Make the paravirtual cpuid enforcement mechanism idempotent to ioctl()
ordering by updating pv_cpuid.features whenever userspace requests the
capability. Extract this update out of kvm_update_cpuid_runtime() into a
new helper function and move its other call site into
kvm_vcpu_after_set_cpuid() where it more likely belongs.

Fixes: 66570e96 ("kvm: x86: only provide PV features if enabled in guest's CPUID")
Signed-off-by: default avatarOliver Upton <oupton@google.com>
Reviewed-by: default avatarPeter Shier <pshier@google.com>
Message-Id: <20201027231044.655110-5-oupton@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 1930e5dd

arch/x86/kvm/cpuid.c

+16 −7
Original line number Diff line number Diff line
@@ -90,6 +90,20 @@ static int kvm_check_cpuid(struct kvm_cpuid_entry2 *entries, int nent) 
	return 0;

}



void kvm_update_pv_runtime(struct kvm_vcpu *vcpu)

{

	struct kvm_cpuid_entry2 *best;



	best = kvm_find_cpuid_entry(vcpu, KVM_CPUID_FEATURES, 0);



	/*

	 * save the feature bitmap to avoid cpuid lookup for every PV

	 * operation

	 */

	if (best)

		vcpu->arch.pv_cpuid.features = best->eax;

}



void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu)

{

	struct kvm_cpuid_entry2 *best;
@@ -124,13 +138,6 @@ void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu) 
		(best->eax & (1 << KVM_FEATURE_PV_UNHALT)))

		best->eax &= ~(1 << KVM_FEATURE_PV_UNHALT);



	/*

	 * save the feature bitmap to avoid cpuid lookup for every PV

	 * operation

	 */

	if (best)

		vcpu->arch.pv_cpuid.features = best->eax;



	if (!kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT)) {

		best = kvm_find_cpuid_entry(vcpu, 0x1, 0);

		if (best)
@@ -162,6 +169,8 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) 
		vcpu->arch.guest_supported_xcr0 =

			(best->eax | ((u64)best->edx << 32)) & supported_xcr0;



	kvm_update_pv_runtime(vcpu);



	vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);

	kvm_mmu_reset_context(vcpu);

arch/x86/kvm/cpuid.h

+1 −0
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ extern u32 kvm_cpu_caps[NCAPINTS] __read_mostly; 
void kvm_set_cpu_caps(void);



void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu);

void kvm_update_pv_runtime(struct kvm_vcpu *vcpu);

struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,

					      u32 function, u32 index);

int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,

arch/x86/kvm/x86.c

+2 −0
Original line number Diff line number Diff line
@@ -4611,6 +4611,8 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu, 


	case KVM_CAP_ENFORCE_PV_FEATURE_CPUID:

		vcpu->arch.pv_cpuid.enforce = cap->args[0];

		if (vcpu->arch.pv_cpuid.enforce)

			kvm_update_pv_runtime(vcpu);



		return 0;