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Subject[PATCH 3/6] KVM: nVMX: properly handle errors in nested_vmx_handle_enlightened_vmptrld()
Date
nested_vmx_handle_enlightened_vmptrld() fails in two cases:
- when we fail to kvm_vcpu_map() the supplied GPA
- when revision_id is incorrect.
Genuine Hyper-V raises #UD in the former case (at least with *some*
incorrect GPAs) and does VMfailInvalid() in the later. KVM doesn't do
anything so L1 just gets stuck retrying the same faulty VMLAUNCH.

nested_vmx_handle_enlightened_vmptrld() has two call sites:
nested_vmx_run() and nested_get_vmcs12_pages(). The former needs to queue
do much: the failure there happens after migration when L2 was running (and
L1 did something weird like wrote to VP assist page from a different vCPU),
just kill L1 with KVM_EXIT_INTERNAL_ERROR.

Reported-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/kvm/vmx/evmcs.h | 7 +++++++
arch/x86/kvm/vmx/nested.c | 39 +++++++++++++++++++++++++++++----------
2 files changed, 36 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/vmx/evmcs.h b/arch/x86/kvm/vmx/evmcs.h
index 6de47f2569c9..e5f7a7ebf27d 100644
--- a/arch/x86/kvm/vmx/evmcs.h
+++ b/arch/x86/kvm/vmx/evmcs.h
@@ -198,6 +198,13 @@ static inline void evmcs_sanitize_exec_ctrls(struct vmcs_config *vmcs_conf) {}
static inline void evmcs_touch_msr_bitmap(void) {}
#endif /* IS_ENABLED(CONFIG_HYPERV) */

+enum nested_evmptrld_status {
+ EVMPTRLD_DISABLED,
+ EVMPTRLD_SUCCEEDED,
+ EVMPTRLD_VMFAIL,
+ EVMPTRLD_ERROR,
+};
+
bool nested_enlightened_vmentry(struct kvm_vcpu *vcpu, u64 *evmcs_gpa);
uint16_t nested_get_evmcs_version(struct kvm_vcpu *vcpu);
int nested_enable_evmcs(struct kvm_vcpu *vcpu,
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 72398e3bc92b..65df8bcbb9c8 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -1910,18 +1910,18 @@ static int copy_vmcs12_to_enlightened(struct vcpu_vmx *vmx)
* This is an equivalent of the nested hypervisor executing the vmptrld
* instruction.
*/
-static int nested_vmx_handle_enlightened_vmptrld(struct kvm_vcpu *vcpu,
- bool from_launch)
+enum nested_evmptrld_status nested_vmx_handle_enlightened_vmptrld(
+ struct kvm_vcpu *vcpu, bool from_launch)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
bool evmcs_gpa_changed = false;
u64 evmcs_gpa;

if (likely(!vmx->nested.enlightened_vmcs_enabled))
- return 1;
+ return EVMPTRLD_DISABLED;

if (!nested_enlightened_vmentry(vcpu, &evmcs_gpa))
- return 1;
+ return EVMPTRLD_DISABLED;

if (unlikely(!vmx->nested.hv_evmcs ||
evmcs_gpa != vmx->nested.hv_evmcs_vmptr)) {
@@ -1932,7 +1932,7 @@ static int nested_vmx_handle_enlightened_vmptrld(struct kvm_vcpu *vcpu,

if (kvm_vcpu_map(vcpu, gpa_to_gfn(evmcs_gpa),
&vmx->nested.hv_evmcs_map))
- return 0;
+ return EVMPTRLD_ERROR;

vmx->nested.hv_evmcs = vmx->nested.hv_evmcs_map.hva;

@@ -1961,7 +1961,7 @@ static int nested_vmx_handle_enlightened_vmptrld(struct kvm_vcpu *vcpu,
if ((vmx->nested.hv_evmcs->revision_id != KVM_EVMCS_VERSION) &&
(vmx->nested.hv_evmcs->revision_id != VMCS12_REVISION)) {
nested_release_evmcs(vcpu);
- return 0;
+ return EVMPTRLD_VMFAIL;
}

vmx->nested.dirty_vmcs12 = true;
@@ -1990,7 +1990,7 @@ static int nested_vmx_handle_enlightened_vmptrld(struct kvm_vcpu *vcpu,
vmx->nested.hv_evmcs->hv_clean_fields &=
~HV_VMX_ENLIGHTENED_CLEAN_FIELD_ALL;

- return 1;
+ return EVMPTRLD_SUCCEEDED;
}

void nested_sync_vmcs12_to_shadow(struct kvm_vcpu *vcpu)
@@ -3050,8 +3050,21 @@ static bool nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
* L2 was running), map it here to make sure vmcs12 changes are
* properly reflected.
*/
- if (vmx->nested.enlightened_vmcs_enabled && !vmx->nested.hv_evmcs)
- nested_vmx_handle_enlightened_vmptrld(vcpu, false);
+ if (vmx->nested.enlightened_vmcs_enabled && !vmx->nested.hv_evmcs) {
+ enum nested_evmptrld_status evmptrld_status =
+ nested_vmx_handle_enlightened_vmptrld(vcpu, false);
+
+ if (evmptrld_status == EVMPTRLD_VMFAIL ||
+ evmptrld_status == EVMPTRLD_ERROR) {
+ pr_debug_ratelimited("%s: enlightened vmptrld failed\n",
+ __func__);
+ vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+ vcpu->run->internal.suberror =
+ KVM_INTERNAL_ERROR_EMULATION;
+ vcpu->run->internal.ndata = 0;
+ return false;
+ }
+ }

if (nested_cpu_has2(vmcs12, SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES)) {
/*
@@ -3316,12 +3329,18 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
enum nvmx_vmentry_status status;
struct vcpu_vmx *vmx = to_vmx(vcpu);
u32 interrupt_shadow = vmx_get_interrupt_shadow(vcpu);
+ enum nested_evmptrld_status evmptrld_status;

if (!nested_vmx_check_permission(vcpu))
return 1;

- if (!nested_vmx_handle_enlightened_vmptrld(vcpu, launch))
+ evmptrld_status = nested_vmx_handle_enlightened_vmptrld(vcpu, launch);
+ if (evmptrld_status == EVMPTRLD_ERROR) {
+ kvm_queue_exception(vcpu, UD_VECTOR);
return 1;
+ } else if (evmptrld_status == EVMPTRLD_VMFAIL) {
+ return nested_vmx_failInvalid(vcpu);
+ }

if (!vmx->nested.hv_evmcs && vmx->nested.current_vmptr == -1ull)
return nested_vmx_failInvalid(vcpu);
--
2.24.1
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