The only thing that makes me unhappy about this is that the KVM_SET_SREGS ioctl may modify some VCPU state before returning -EINVAL. I could hoist the call to kvm_set_apic_base, but that only works for one mutator. If this doesn't bother anyone else, I'll just leave it where it is. On Wed, Aug 9, 2017 at 2:13 AM, David Hildenbrand <david@xxxxxxxxxx> wrote: > On 09.08.2017 01:27, Jim Mattson wrote: >> Host-initiated writes to the IA32_APIC_BASE MSR do not have to follow >> local APIC state transition constraints, but the value written must be >> valid. >> >> Signed-off-by: Jim Mattson <jmattson@xxxxxxxxxx> >> --- >> arch/x86/kvm/x86.c | 10 ++++++---- >> 1 file changed, 6 insertions(+), 4 deletions(-) >> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >> index d734aa8c5b4f..fb786d9feef1 100644 >> --- a/arch/x86/kvm/x86.c >> +++ b/arch/x86/kvm/x86.c >> @@ -313,10 +313,11 @@ int kvm_set_apic_base(struct kvm_vcpu *vcpu, struct msr_data *msr_info) >> u64 reserved_bits = ((~0ULL) << cpuid_maxphyaddr(vcpu)) | >> 0x2ff | (guest_cpuid_has_x2apic(vcpu) ? 0 : X2APIC_ENABLE); >> >> + if ((msr_info->data & reserved_bits) != 0 || >> + new_state == X2APIC_ENABLE) > > I'd drop the != 0 here and fit it into one line. > >> + return 1; >> if (!msr_info->host_initiated && >> - ((msr_info->data & reserved_bits) != 0 || >> - new_state == X2APIC_ENABLE || >> - (new_state == MSR_IA32_APICBASE_ENABLE && >> + ((new_state == MSR_IA32_APICBASE_ENABLE && >> old_state == (MSR_IA32_APICBASE_ENABLE | X2APIC_ENABLE)) || >> (new_state == (MSR_IA32_APICBASE_ENABLE | X2APIC_ENABLE) && >> old_state == 0))) >> @@ -7444,7 +7445,8 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu, >> kvm_x86_ops->set_efer(vcpu, sregs->efer); >> apic_base_msr.data = sregs->apic_base; >> apic_base_msr.host_initiated = true; >> - kvm_set_apic_base(vcpu, &apic_base_msr); >> + if (kvm_set_apic_base(vcpu, &apic_base_msr)) >> + return -EINVAL; > > I assume we don't have to document this new behavior. > >> >> mmu_reset_needed |= kvm_read_cr0(vcpu) != sregs->cr0; >> kvm_x86_ops->set_cr0(vcpu, sregs->cr0); >> > > From what I can tell, this looks good to me. > > -- > > Thanks, > > David
