MSR accesses can be one of:
(1) KVM internal access,
(2) userspace access (e.g., via KVM_SET_MSRS ioctl),
(3) guest access.
The ignore_msrs was previously handled by kvm_get_msr_common() and
kvm_set_msr_common(), which is the bottom of the msr access stack. It's
working in most cases, however it could dump unwanted warning messages to dmesg
even if kvm get/set the msrs internally when calling __kvm_set_msr() or
__kvm_get_msr() (e.g. kvm_cpuid()). Ideally we only want to trap cases (2)
or (3), but not (1) above.
To achieve this, move the ignore_msrs handling upper until the callers of
__kvm_get_msr() and __kvm_set_msr(). To identify the "msr missing" event, a
new return value (KVM_MSR_RET_INVALID==2) is used for that.
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
---
arch/x86/kvm/x86.c | 80 +++++++++++++++++++++++++++++++---------------
arch/x86/kvm/x86.h | 2 ++
2 files changed, 56 insertions(+), 26 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c17e6eb9ad43..b49eaf8a2ce5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -245,6 +245,29 @@ EXPORT_SYMBOL_GPL(x86_fpu_cache);
static struct kmem_cache *x86_emulator_cache;
+/*
+ * When called, it means the previous get/set msr reached an invalid msr.
+ * Return 0 if we want to ignore/silent this failed msr access, or 1 if we want
+ * to fail the caller.
+ */
+static int kvm_msr_ignored_check(struct kvm_vcpu *vcpu, u32 msr,
+ u64 data, bool write)
+{
+ const char *op = write ? "wrmsr" : "rdmsr";
+
+ if (ignore_msrs) {
+ if (report_ignored_msrs)
+ vcpu_unimpl(vcpu, "ignored %s: 0x%x data 0x%llx\n",
+ op, msr, data);
+ /* Mask the error */
+ return 0;
+ } else {
+ vcpu_debug_ratelimited(vcpu, "unhandled %s: 0x%x data 0x%llx\n",
+ op, msr, data);
+ return 1;
+ }
+}
+
static struct kmem_cache *kvm_alloc_emulator_cache(void)
{
unsigned int useroffset = offsetof(struct x86_emulate_ctxt, src);
@@ -1496,6 +1519,17 @@ static int __kvm_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data,
return kvm_x86_ops.set_msr(vcpu, &msr);
}
+static int kvm_set_msr_ignored_check(struct kvm_vcpu *vcpu,
+ u32 index, u64 data, bool host_initiated)
+{
+ int ret = __kvm_set_msr(vcpu, index, data, host_initiated);
+
+ if (ret == KVM_MSR_RET_INVALID)
+ ret = kvm_msr_ignored_check(vcpu, index, data, true);
+
+ return ret;
+}
+
/*
* Read the MSR specified by @index into @data. Select MSR specific fault
* checks are bypassed if @host_initiated is %true.
@@ -1517,15 +1551,29 @@ int __kvm_get_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data,
return ret;
}
+static int kvm_get_msr_ignored_check(struct kvm_vcpu *vcpu,
+ u32 index, u64 *data, bool host_initiated)
+{
+ int ret = __kvm_get_msr(vcpu, index, data, host_initiated);
+
+ if (ret == KVM_MSR_RET_INVALID) {
+ /* Unconditionally clear *data for simplicity */
+ *data = 0;
+ ret = kvm_msr_ignored_check(vcpu, index, 0, false);
+ }
+
+ return ret;
+}
+
int kvm_get_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data)
{
- return __kvm_get_msr(vcpu, index, data, false);
+ return kvm_get_msr_ignored_check(vcpu, index, data, false);
}
EXPORT_SYMBOL_GPL(kvm_get_msr);
int kvm_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data)
{
- return __kvm_set_msr(vcpu, index, data, false);
+ return kvm_set_msr_ignored_check(vcpu, index, data, false);
}
EXPORT_SYMBOL_GPL(kvm_set_msr);
@@ -1621,12 +1669,12 @@ EXPORT_SYMBOL_GPL(handle_fastpath_set_msr_irqoff);
*/
static int do_get_msr(struct kvm_vcpu *vcpu, unsigned index, u64 *data)
{
- return __kvm_get_msr(vcpu, index, data, true);
+ return kvm_get_msr_ignored_check(vcpu, index, data, true);
}
static int do_set_msr(struct kvm_vcpu *vcpu, unsigned index, u64 *data)
{
- return __kvm_set_msr(vcpu, index, *data, true);
+ return kvm_set_msr_ignored_check(vcpu, index, *data, true);
}
#ifdef CONFIG_X86_64
@@ -2977,17 +3025,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
return xen_hvm_config(vcpu, data);
if (kvm_pmu_is_valid_msr(vcpu, msr))
return kvm_pmu_set_msr(vcpu, msr_info);
- if (!ignore_msrs) {
- vcpu_debug_ratelimited(vcpu, "unhandled wrmsr: 0x%x data 0x%llx\n",
- msr, data);
- return 1;
- } else {
- if (report_ignored_msrs)
- vcpu_unimpl(vcpu,
- "ignored wrmsr: 0x%x data 0x%llx\n",
- msr, data);
- break;
- }
+ return KVM_MSR_RET_INVALID;
}
return 0;
}
@@ -3234,17 +3272,7 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
default:
if (kvm_pmu_is_valid_msr(vcpu, msr_info->index))
return kvm_pmu_get_msr(vcpu, msr_info->index, &msr_info->data);
- if (!ignore_msrs) {
- vcpu_debug_ratelimited(vcpu, "unhandled rdmsr: 0x%x\n",
- msr_info->index);
- return 1;
- } else {
- if (report_ignored_msrs)
- vcpu_unimpl(vcpu, "ignored rdmsr: 0x%x\n",
- msr_info->index);
- msr_info->data = 0;
- }
- break;
+ return KVM_MSR_RET_INVALID;
}
return 0;
}
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index b968acc0516f..62e3e896d059 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -359,4 +359,6 @@ void kvm_load_guest_xsave_state(struct kvm_vcpu *vcpu);
void kvm_load_host_xsave_state(struct kvm_vcpu *vcpu);
u64 kvm_spec_ctrl_valid_bits(struct kvm_vcpu *vcpu);
+#define KVM_MSR_RET_INVALID 2
+
#endif
--
2.26.2
