Commit 18964092 authored Jul 08, 2020 by Xiaoyao Li Committed by Paolo Bonzini Jul 08, 2020

KVM: X86: Reset vcpu->arch.cpuid_nent to 0 if SET_CPUID* fails



Current implementation keeps userspace input of CPUID configuration and
cpuid->nent even if kvm_update_cpuid() fails. Reset vcpu->arch.cpuid_nent
to 0 for the case of failure as a simple fix.

Besides, update the doc to explicitly state that if IOCTL SET_CPUID*
fail KVM gives no gurantee that previous valid CPUID configuration is
kept.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Message-Id: <20200708065054.19713-2-xiaoyao.li@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

parent 2e8cd7a3

Documentation/virt/kvm/api.rst

+4 −0

Original line number	Diff line number	Diff line
		@@ -669,6 +669,10 @@ MSRs that have been set successfully.
		Defines the vcpu responses to the cpuid instruction. Applications
		should use the KVM_SET_CPUID2 ioctl if available.

		Note, when this IOCTL fails, KVM gives no guarantees that previous valid CPUID
		configuration (if there is) is not corrupted. Userspace can get a copy of the
		resulting CPUID configuration through KVM_GET_CPUID2 in case.

		::

		struct kvm_cpuid_entry {

arch/x86/kvm/cpuid.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -209,6 +209,8 @@ int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
		kvm_apic_set_version(vcpu);
		kvm_x86_ops.cpuid_update(vcpu);
		r = kvm_update_cpuid(vcpu);
		if (r)
		vcpu->arch.cpuid_nent = 0;

		kvfree(cpuid_entries);
		out:
		@@ -232,6 +234,8 @@ int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
		kvm_apic_set_version(vcpu);
		kvm_x86_ops.cpuid_update(vcpu);
		r = kvm_update_cpuid(vcpu);
		if (r)
		vcpu->arch.cpuid_nent = 0;
		out:
		return r;
		}