Add support for exiting to userspace on a rdmsr or wrmsr instruction if
the MSR being read from or written to is in the user_exit_msrs list.
Signed-off-by: Aaron Lewis <aaronlewis@xxxxxxxxxx>
---
v2 -> v3
- Refactored commit based on Alexander Graf's changes in the first commit
in this series. Changes made were:
- Updated member 'inject_gp' to 'error' based on struct msr in kvm_run.
- Move flag 'vcpu->kvm->arch.user_space_msr_enabled' out of
kvm_msr_user_space() to allow it to work with both methods that bounce
to userspace (msr list and #GP fallback). Updated caller functions
to account for this change.
- trace_kvm_msr has been moved up and combine with a previous call in
complete_emulated_msr() based on the suggestion made by Alexander
Graf <graf@xxxxxxxxxx>.
---
arch/x86/kvm/trace.h | 24 ++++++++++++++
arch/x86/kvm/x86.c | 76 ++++++++++++++++++++++++++++++++++++++------
2 files changed, 90 insertions(+), 10 deletions(-)
diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
index b66432b015d2..755610befbb5 100644
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -367,6 +367,30 @@ TRACE_EVENT(kvm_msr,
#define trace_kvm_msr_read_ex(ecx) trace_kvm_msr(0, ecx, 0, true)
#define trace_kvm_msr_write_ex(ecx, data) trace_kvm_msr(1, ecx, data, true)
+TRACE_EVENT(kvm_userspace_msr,
+ TP_PROTO(bool is_write, u8 error, u32 index, u64 data),
+ TP_ARGS(is_write, error, index, data),
+
+ TP_STRUCT__entry(
+ __field(bool, is_write)
+ __field(u8, error)
+ __field(u32, index)
+ __field(u64, data)
+ ),
+
+ TP_fast_assign(
+ __entry->is_write = is_write;
+ __entry->error = error;
+ __entry->index = index;
+ __entry->data = data;
+ ),
+
+ TP_printk("userspace %s %x = 0x%llx, %s",
+ __entry->is_write ? "wrmsr" : "rdmsr",
+ __entry->index, __entry->data,
+ __entry->error ? "error" : "no_error")
+);
+
/*
* Tracepoint for guest CR access.
*/
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e349d51d5d65..b370b3f4b4f3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -109,6 +109,8 @@ static void __kvm_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags);
static void store_regs(struct kvm_vcpu *vcpu);
static int sync_regs(struct kvm_vcpu *vcpu);
+bool kvm_msr_user_exit(struct kvm *kvm, u32 index);
+
struct kvm_x86_ops kvm_x86_ops __read_mostly;
EXPORT_SYMBOL_GPL(kvm_x86_ops);
@@ -1629,11 +1631,19 @@ EXPORT_SYMBOL_GPL(kvm_set_msr);
static int complete_emulated_msr(struct kvm_vcpu *vcpu, bool is_read)
{
- if (vcpu->run->msr.error) {
+ u32 ecx = vcpu->run->msr.index;
+ u64 data = vcpu->run->msr.data;
+ u8 error = vcpu->run->msr.error;
+
+ trace_kvm_userspace_msr(!is_read, error, ecx, data);
+ trace_kvm_msr(!is_read, ecx, data, !!error);
+
+ if (error) {
kvm_inject_gp(vcpu, 0);
+ return 1;
} else if (is_read) {
- kvm_rax_write(vcpu, (u32)vcpu->run->msr.data);
- kvm_rdx_write(vcpu, vcpu->run->msr.data >> 32);
+ kvm_rax_write(vcpu, (u32)data);
+ kvm_rdx_write(vcpu, data >> 32);
}
return kvm_skip_emulated_instruction(vcpu);
@@ -1653,9 +1663,6 @@ static int kvm_msr_user_space(struct kvm_vcpu *vcpu, u32 index,
u32 exit_reason, u64 data,
int (*completion)(struct kvm_vcpu *vcpu))
{
- if (!vcpu->kvm->arch.user_space_msr_enabled)
- return 0;
-
vcpu->run->exit_reason = exit_reason;
vcpu->run->msr.error = 0;
vcpu->run->msr.pad[0] = 0;
@@ -1686,10 +1693,18 @@ int kvm_emulate_rdmsr(struct kvm_vcpu *vcpu)
u64 data;
int r;
+ if (kvm_msr_user_exit(vcpu->kvm, ecx)) {
+ kvm_get_msr_user_space(vcpu, ecx);
+ /* Bounce to user space */
+ return 0;
+ }
+
+
r = kvm_get_msr(vcpu, ecx, &data);
/* MSR read failed? See if we should ask user space */
- if (r && kvm_get_msr_user_space(vcpu, ecx)) {
+ if (r && vcpu->kvm->arch.user_space_msr_enabled) {
+ kvm_get_msr_user_space(vcpu, ecx);
/* Bounce to user space */
return 0;
}
@@ -1715,10 +1730,17 @@ int kvm_emulate_wrmsr(struct kvm_vcpu *vcpu)
u64 data = kvm_read_edx_eax(vcpu);
int r;
+ if (kvm_msr_user_exit(vcpu->kvm, ecx)) {
+ kvm_set_msr_user_space(vcpu, ecx, data);
+ /* Bounce to user space */
+ return 0;
+ }
+
r = kvm_set_msr(vcpu, ecx, data);
/* MSR write failed? See if we should ask user space */
- if (r && kvm_set_msr_user_space(vcpu, ecx, data)) {
+ if (r && vcpu->kvm->arch.user_space_msr_enabled) {
+ kvm_set_msr_user_space(vcpu, ecx, data);
/* Bounce to user space */
return 0;
}
@@ -3606,6 +3628,25 @@ static int kvm_vm_ioctl_set_exit_msrs(struct kvm *kvm,
return 0;
}
+bool kvm_msr_user_exit(struct kvm *kvm, u32 index)
+{
+ struct kvm_msr_list *exit_msrs;
+ int i;
+
+ exit_msrs = kvm->arch.user_exit_msrs;
+
+ if (!exit_msrs)
+ return false;
+
+ for (i = 0; i < exit_msrs->nmsrs; ++i) {
+ if (exit_msrs->indices[i] == index)
+ return true;
+ }
+
+ return false;
+}
+EXPORT_SYMBOL_GPL(kvm_msr_user_exit);
+
int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
{
int r = 0;
@@ -6640,9 +6681,16 @@ static int emulator_get_msr(struct x86_emulate_ctxt *ctxt,
struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt);
int r;
+ if (kvm_msr_user_exit(vcpu->kvm, msr_index)) {
+ kvm_get_msr_user_space(vcpu, msr_index);
+ /* Bounce to user space */
+ return X86EMUL_IO_NEEDED;
+ }
+
r = kvm_get_msr(vcpu, msr_index, pdata);
- if (r && kvm_get_msr_user_space(vcpu, msr_index)) {
+ if (r && vcpu->kvm->arch.user_space_msr_enabled) {
+ kvm_get_msr_user_space(vcpu, msr_index);
/* Bounce to user space */
return X86EMUL_IO_NEEDED;
}
@@ -6656,9 +6704,16 @@ static int emulator_set_msr(struct x86_emulate_ctxt *ctxt,
struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt);
int r;
+ if (kvm_msr_user_exit(vcpu->kvm, msr_index)) {
+ kvm_set_msr_user_space(vcpu, msr_index, data);
+ /* Bounce to user space */
+ return X86EMUL_IO_NEEDED;
+ }
+
r = kvm_set_msr(emul_to_vcpu(ctxt), msr_index, data);
- if (r && kvm_set_msr_user_space(vcpu, msr_index, data)) {
+ if (r && vcpu->kvm->arch.user_space_msr_enabled) {
+ kvm_set_msr_user_space(vcpu, msr_index, data);
/* Bounce to user space */
return X86EMUL_IO_NEEDED;
}
@@ -11090,3 +11145,4 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_avic_unaccelerated_access);
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_avic_incomplete_ipi);
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_avic_ga_log);
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_apicv_update_request);
+EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_userspace_msr);
--
2.28.0.220.ged08abb693-goog
