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Subject[PATCH 4.18 056/123] KVM: x86: ensure all MSRs can always be KVM_GET/SET_MSRd
Date
4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Paolo Bonzini <pbonzini@redhat.com>

commit 44883f01fe6ae436a8604c47d8435276fef369b0 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/kvm/hyperv.c | 27 ++++++++++++++++++++-------
arch/x86/kvm/hyperv.h | 2 +-
arch/x86/kvm/x86.c | 15 +++++++++------
3 files changed, 30 insertions(+), 14 deletions(-)

--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -235,7 +235,7 @@ static int synic_set_msr(struct kvm_vcpu
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
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_
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_vcp
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_
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_vcp
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_vcp
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_vcp
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)
--- a/arch/x86/kvm/hyperv.h
+++ b/arch/x86/kvm/hyperv.h
@@ -48,7 +48,7 @@ static inline struct kvm_vcpu *synic_to_
}

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);
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2185,10 +2185,11 @@ static int set_msr_mce(struct kvm_vcpu *
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:
@@ -2576,7 +2577,7 @@ int kvm_get_msr(struct kvm_vcpu *vcpu, s
}
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;
@@ -2591,7 +2592,7 @@ static int get_msr_mce(struct kvm_vcpu *
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;
@@ -2724,7 +2725,8 @@ int kvm_get_msr_common(struct kvm_vcpu *
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
@@ -2745,7 +2747,8 @@ int kvm_get_msr_common(struct kvm_vcpu *
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

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