KVM: x86: ensure all MSRs can always be KVM_GET/SET_MSR'd
Some of the MSRs returned by GET_MSR_INDEX_LIST currently cannot be sent back
to KVM_GET_MSR and/or KVM_SET_MSR; either they can never be sent back, or you
they are only accepted under special conditions. This makes the API a pain to
use.
To avoid this pain, this patch makes it so that the result of the get-list
ioctl can always be used for host-initiated get and set. Since we don't have
a separate way to check for read-only MSRs, this means some Hyper-V MSRs are
ignored when written. Arguably they should not even be in the result of
GET_MSR_INDEX_LIST, but I am leaving there in case userspace is using the
outcome of GET_MSR_INDEX_LIST to derive the support for the corresponding
Hyper-V feature.
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2b812b3..6f0fabd 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2160,10 +2160,11 @@ static int set_msr_mce(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
vcpu->arch.mcg_status = data;
break;
case MSR_IA32_MCG_CTL:
- if (!(mcg_cap & MCG_CTL_P))
+ if (!(mcg_cap & MCG_CTL_P) &&
+ (data || !msr_info->host_initiated))
return 1;
if (data != 0 && data != ~(u64)0)
- return -1;
+ return 1;
vcpu->arch.mcg_ctl = data;
break;
default:
@@ -2551,7 +2552,7 @@ int kvm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
}
EXPORT_SYMBOL_GPL(kvm_get_msr);
-static int get_msr_mce(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
+static int get_msr_mce(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata, bool host)
{
u64 data;
u64 mcg_cap = vcpu->arch.mcg_cap;
@@ -2566,7 +2567,7 @@ static int get_msr_mce(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
data = vcpu->arch.mcg_cap;
break;
case MSR_IA32_MCG_CTL:
- if (!(mcg_cap & MCG_CTL_P))
+ if (!(mcg_cap & MCG_CTL_P) && !host)
return 1;
data = vcpu->arch.mcg_ctl;
break;
@@ -2699,7 +2700,8 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
case MSR_IA32_MCG_CTL:
case MSR_IA32_MCG_STATUS:
case MSR_IA32_MC0_CTL ... MSR_IA32_MCx_CTL(KVM_MAX_MCE_BANKS) - 1:
- return get_msr_mce(vcpu, msr_info->index, &msr_info->data);
+ return get_msr_mce(vcpu, msr_info->index, &msr_info->data,
+ msr_info->host_initiated);
case MSR_K7_CLK_CTL:
/*
* Provide expected ramp-up count for K7. All other
@@ -2720,7 +2722,8 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
case HV_X64_MSR_TSC_EMULATION_CONTROL:
case HV_X64_MSR_TSC_EMULATION_STATUS:
return kvm_hv_get_msr_common(vcpu,
- msr_info->index, &msr_info->data);
+ msr_info->index, &msr_info->data,
+ msr_info->host_initiated);
break;
case MSR_IA32_BBL_CR_CTL3:
/* This legacy MSR exists but isn't fully documented in current