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Subject[PATCH] KVM: nVMX: nested MSR auto load/restore emulation.
Some hypervisors need MSR auto load/restore feature.

We read MSRs from vm-entry MSR load area which specified by L1,
and load them via kvm_set_msr in the nested entry.
When nested exit occurs, we get MSRs via kvm_get_msr, writting
them to L1`s MSR store area. After this, we read MSRs from vm-exit
MSR load area, and load them via kvm_set_msr.

VirtualBox will work fine with this patch.

Signed-off-by: Wincy Van <fanwenyi0529@gmail.com>

diff --git a/arch/x86/include/uapi/asm/vmx.h b/arch/x86/include/uapi/asm/vmx.h
index 990a2fe..986af3f 100644
--- a/arch/x86/include/uapi/asm/vmx.h
+++ b/arch/x86/include/uapi/asm/vmx.h
@@ -56,6 +56,7 @@
#define EXIT_REASON_MSR_READ 31
#define EXIT_REASON_MSR_WRITE 32
#define EXIT_REASON_INVALID_STATE 33
+#define EXIT_REASON_MSR_LOAD_FAIL 34
#define EXIT_REASON_MWAIT_INSTRUCTION 36
#define EXIT_REASON_MONITOR_INSTRUCTION 39
#define EXIT_REASON_PAUSE_INSTRUCTION 40
@@ -114,8 +115,12 @@
{ EXIT_REASON_APIC_WRITE, "APIC_WRITE" }, \
{ EXIT_REASON_EOI_INDUCED, "EOI_INDUCED" }, \
{ EXIT_REASON_INVALID_STATE, "INVALID_STATE" }, \
+ { EXIT_REASON_MSR_LOAD_FAIL, "MSR_LOAD_FAIL" }, \
{ EXIT_REASON_INVD, "INVD" }, \
{ EXIT_REASON_INVVPID, "INVVPID" }, \
{ EXIT_REASON_INVPCID, "INVPCID" }

+#define VMX_ABORT_SAVE_GUEST_MSR_FAIL 1
+#define VMX_ABORT_LOAD_HOST_MSR_FAIL 4
+
#endif /* _UAPIVMX_H */
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 6a951d8..377e405 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6088,6 +6088,13 @@ static void nested_vmx_failValid(struct kvm_vcpu *vcpu,
*/
}

+static void nested_vmx_abort(struct kvm_vcpu *vcpu, u32 indicator)
+{
+ /* TODO: not to simply reset guest here. */
+ kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
+ printk(KERN_WARNING"kvm: nested vmx abort, indicator %d\n", indicator);
+}
+
static enum hrtimer_restart vmx_preemption_timer_fn(struct hrtimer *timer)
{
struct vcpu_vmx *vmx =
@@ -8215,6 +8222,88 @@ static void vmx_start_preemption_timer(struct
kvm_vcpu *vcpu)
ns_to_ktime(preemption_timeout), HRTIMER_MODE_REL);
}

+static inline int nested_msr_check_common(struct vmx_msr_entry *e)
+{
+ if (e->index >> 8 == 0x8 || e->reserved != 0)
+ return -EINVAL;
+ return 0;
+}
+
+static inline int nested_load_msr_check(struct vmx_msr_entry *e)
+{
+ if (e->index == MSR_FS_BASE ||
+ e->index == MSR_GS_BASE ||
+ nested_msr_check_common(e))
+ return -EINVAL;
+ return 0;
+}
+
+/* load guest msr at nested entry.
+ * return 0 for success, entry index for failed.
+ */
+static u32 nested_entry_load_msr(struct kvm_vcpu *vcpu, u64 gpa, u32 count)
+{
+ u32 i = 0;
+ struct vmx_msr_entry e;
+ struct msr_data msr;
+
+ msr.host_initiated = false;
+ while (i < count) {
+ kvm_read_guest(vcpu->kvm, gpa + i * sizeof(struct vmx_msr_entry),
+ &e, sizeof(struct vmx_msr_entry));
+ if (nested_load_msr_check(&e))
+ goto fail;
+ msr.index = e.index;
+ msr.data = e.value;
+ if (kvm_set_msr(vcpu, &msr))
+ goto fail;
+ ++i;
+ }
+ return 0;
+fail:
+ return i + 1;
+}
+
+static int nested_exit_store_msr(struct kvm_vcpu *vcpu, u64 gpa, u32 count)
+{
+ u32 i = 0;
+ struct vmx_msr_entry e;
+
+ while (i < count) {
+ kvm_read_guest(vcpu->kvm, gpa + i * sizeof(struct vmx_msr_entry),
+ &e, sizeof(struct vmx_msr_entry));
+ if (nested_msr_check_common(&e))
+ return -EINVAL;
+ if (kvm_get_msr(vcpu, e.index, &e.value))
+ return -EINVAL;
+ kvm_write_guest(vcpu->kvm, gpa + i * sizeof(struct vmx_msr_entry),
+ &e, sizeof(struct vmx_msr_entry));
+ ++i;
+ }
+ return 0;
+}
+
+static int nested_exit_load_msr(struct kvm_vcpu *vcpu, u64 gpa, u32 count)
+{
+ u32 i = 0;
+ struct vmx_msr_entry e;
+ struct msr_data msr;
+
+ msr.host_initiated = false;
+ while (i < count) {
+ kvm_read_guest(vcpu->kvm, gpa + i * sizeof(struct vmx_msr_entry),
+ &e, sizeof(struct vmx_msr_entry));
+ if (nested_load_msr_check(&e))
+ return -EINVAL;
+ msr.index = e.index;
+ msr.data = e.value;
+ if (kvm_set_msr(vcpu, &msr))
+ return -EINVAL;
+ ++i;
+ }
+ return 0;
+}
+
/*
* prepare_vmcs02 is called when the L1 guest hypervisor runs its nested
* L2 guest. L1 has a vmcs for L2 (vmcs12), and this function "merges" it
@@ -8509,6 +8598,7 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu,
bool launch)
int cpu;
struct loaded_vmcs *vmcs02;
bool ia32e;
+ u32 msr_entry_idx;

if (!nested_vmx_check_permission(vcpu) ||
!nested_vmx_check_vmcs12(vcpu))
@@ -8556,11 +8646,12 @@ static int nested_vmx_run(struct kvm_vcpu
*vcpu, bool launch)
return 1;
}

- if (vmcs12->vm_entry_msr_load_count > 0 ||
- vmcs12->vm_exit_msr_load_count > 0 ||
- vmcs12->vm_exit_msr_store_count > 0) {
- pr_warn_ratelimited("%s: VMCS MSR_{LOAD,STORE} unsupported\n",
- __func__);
+ if ((vmcs12->vm_entry_msr_load_count > 0 &&
+ !IS_ALIGNED(vmcs12->vm_entry_msr_load_addr, 16)) ||
+ (vmcs12->vm_exit_msr_load_count > 0 &&
+ !IS_ALIGNED(vmcs12->vm_exit_msr_load_addr, 16)) ||
+ (vmcs12->vm_exit_msr_store_count > 0 &&
+ !IS_ALIGNED(vmcs12->vm_exit_msr_store_addr, 16))) {
nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD);
return 1;
}
@@ -8666,10 +8757,20 @@ static int nested_vmx_run(struct kvm_vcpu
*vcpu, bool launch)

vmx_segment_cache_clear(vmx);

- vmcs12->launch_state = 1;
-
prepare_vmcs02(vcpu, vmcs12);

+ msr_entry_idx = nested_entry_load_msr(vcpu, vmcs12->vm_entry_msr_load_addr,
+ vmcs12->vm_entry_msr_load_count);
+ if (msr_entry_idx) {
+ leave_guest_mode(vcpu);
+ vmx_load_vmcs01(vcpu);
+ nested_vmx_entry_failure(vcpu, vmcs12,
+ EXIT_REASON_MSR_LOAD_FAIL, msr_entry_idx);
+ return 1;
+ }
+
+ vmcs12->launch_state = 1;
+
if (vmcs12->guest_activity_state == GUEST_ACTIVITY_HLT)
return kvm_emulate_halt(vcpu);

@@ -9097,6 +9198,10 @@ static void load_vmcs12_host_state(struct kvm_vcpu *vcpu,

kvm_set_dr(vcpu, 7, 0x400);
vmcs_write64(GUEST_IA32_DEBUGCTL, 0);
+
+ if (nested_exit_load_msr(vcpu, vmcs12->vm_exit_msr_load_addr,
+ vmcs12->vm_exit_msr_load_count))
+ nested_vmx_abort(vcpu, VMX_ABORT_LOAD_HOST_MSR_FAIL);
}

/*
@@ -9118,6 +9223,10 @@ static void nested_vmx_vmexit(struct kvm_vcpu
*vcpu, u32 exit_reason,
prepare_vmcs12(vcpu, vmcs12, exit_reason, exit_intr_info,
exit_qualification);

+ if (nested_exit_store_msr(vcpu, vmcs12->vm_exit_msr_store_addr,
+ vmcs12->vm_exit_msr_store_count))
+ nested_vmx_abort(vcpu, VMX_ABORT_SAVE_GUEST_MSR_FAIL);
+
vmx_load_vmcs01(vcpu);

if ((exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a8f53a6..1c7eecc 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2323,6 +2323,7 @@ int kvm_get_msr(struct kvm_vcpu *vcpu, u32
msr_index, u64 *pdata)
{
return kvm_x86_ops->get_msr(vcpu, msr_index, pdata);
}
+EXPORT_SYMBOL_GPL(kvm_get_msr);

static int get_msr_mtrr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
{
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 751ece6..be02556 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1585,6 +1585,7 @@ int kvm_write_guest(struct kvm *kvm, gpa_t gpa,
const void *data,
}
return 0;
}
+EXPORT_SYMBOL_GPL(kvm_write_guest);

int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
gpa_t gpa, unsigned long len)

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