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/hyperv.c b/arch/x86/kvm/hyperv.c
index af8caf965baa291319a7e5825b27ab28f97a24cf..01d209ab5481b0edddb020bbc4b701f4c27d3055 100644 (file)
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -235,7 +235,7 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic,
        struct kvm_vcpu *vcpu = synic_to_vcpu(synic);
        int ret;
 
-       if (!synic->active)
+       if (!synic->active && !host)
                return 1;
 
        trace_kvm_hv_synic_set_msr(vcpu->vcpu_id, msr, data, host);
@@ -295,11 +295,12 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic,
        return ret;
 }
 
-static int synic_get_msr(struct kvm_vcpu_hv_synic *synic, u32 msr, u64 *pdata)
+static int synic_get_msr(struct kvm_vcpu_hv_synic *synic, u32 msr, u64 *pdata,
+                        bool host)
 {
        int ret;
 
-       if (!synic->active)
+       if (!synic->active && !host)
                return 1;
 
        ret = 0;
@@ -1014,6 +1015,11 @@ static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data,
        case HV_X64_MSR_TSC_EMULATION_STATUS:
                hv->hv_tsc_emulation_status = data;
                break;
+       case HV_X64_MSR_TIME_REF_COUNT:
+               /* read-only, but still ignore it if host-initiated */
+               if (!host)
+                       return 1;
+               break;
        default:
                vcpu_unimpl(vcpu, "Hyper-V uhandled wrmsr: 0x%x data 0x%llx\n",
                            msr, data);
@@ -1101,6 +1107,12 @@ static int kvm_hv_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host)
                return stimer_set_count(vcpu_to_stimer(vcpu, timer_index),
                                        data, host);
        }
+       case HV_X64_MSR_TSC_FREQUENCY:
+       case HV_X64_MSR_APIC_FREQUENCY:
+               /* read-only, but still ignore it if host-initiated */
+               if (!host)
+                       return 1;
+               break;
        default:
                vcpu_unimpl(vcpu, "Hyper-V uhandled wrmsr: 0x%x data 0x%llx\n",
                            msr, data);
@@ -1156,7 +1168,8 @@ static int kvm_hv_get_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
        return 0;
 }
 
-static int kvm_hv_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
+static int kvm_hv_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata,
+                         bool host)
 {
        u64 data = 0;
        struct kvm_vcpu_hv *hv = &vcpu->arch.hyperv;
@@ -1183,7 +1196,7 @@ static int kvm_hv_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
        case HV_X64_MSR_SIMP:
        case HV_X64_MSR_EOM:
        case HV_X64_MSR_SINT0 ... HV_X64_MSR_SINT15:
-               return synic_get_msr(vcpu_to_synic(vcpu), msr, pdata);
+               return synic_get_msr(vcpu_to_synic(vcpu), msr, pdata, host);
        case HV_X64_MSR_STIMER0_CONFIG:
        case HV_X64_MSR_STIMER1_CONFIG:
        case HV_X64_MSR_STIMER2_CONFIG:
@@ -1229,7 +1242,7 @@ int kvm_hv_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host)
                return kvm_hv_set_msr(vcpu, msr, data, host);
 }
 
-int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
+int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata, bool host)
 {
        if (kvm_hv_msr_partition_wide(msr)) {
                int r;
@@ -1239,7 +1252,7 @@ int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
                mutex_unlock(&vcpu->kvm->arch.hyperv.hv_lock);
                return r;
        } else
-               return kvm_hv_get_msr(vcpu, msr, pdata);
+               return kvm_hv_get_msr(vcpu, msr, pdata, host);
 }
 
 static __always_inline int get_sparse_bank_no(u64 valid_bank_mask, int bank_no)

diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
index 837465d69c6d894ae895680deda4675184811ac6..d6aa969e20f19f518e420be2ff9d8b7f91282994 100644 (file)
--- a/arch/x86/kvm/hyperv.h
+++ b/arch/x86/kvm/hyperv.h
@@ -48,7 +48,7 @@ static inline struct kvm_vcpu *synic_to_vcpu(struct kvm_vcpu_hv_synic *synic)
 }
 
 int kvm_hv_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host);
-int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata);
+int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata, bool host);
 
 bool kvm_hv_hypercall_enabled(struct kvm *kvm);
 int kvm_hv_hypercall(struct kvm_vcpu *vcpu);

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2b812b3c50881d2b42738792a7ef1a72cdcb9d66..6f0fabdb21092852b3e4f0b6a67a7b69197d3689 100644 (file)
--- 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