When exception payloads are enabled by userspace (which is not yet
possible) and a #PF is raised in L2, defer the setting of CR2 until
the #PF is delivered. This allows the L1 hypervisor to intercept the
fault before CR2 is modified.
For backwards compatibility, when exception payloads are not enabled
by userspace, kvm_multiple_exception modifies CR2 when the #PF
exception is raised.
Reported-by: Jim Mattson <jmattson@xxxxxxxxxx>
Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Jim Mattson <jmattson@xxxxxxxxxx>
---
arch/x86/kvm/svm.c | 13 ++++++------
arch/x86/kvm/vmx.c | 19 +++++++++---------
arch/x86/kvm/x86.c | 49 ++++++++++++++++++++++++++++++++++++++++++----
arch/x86/kvm/x86.h | 2 ++
4 files changed, 62 insertions(+), 21 deletions(-)
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 61ccfb13899e..6079e4dec263 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -809,6 +809,8 @@ static void svm_queue_exception(struct kvm_vcpu *vcpu)
nested_svm_check_exception(svm, nr, has_error_code, error_code))
return;
+ kvm_deliver_exception_payload(&svm->vcpu);
+
if (nr == BP_VECTOR && !static_cpu_has(X86_FEATURE_NRIPS)) {
unsigned long rip, old_rip = kvm_rip_read(&svm->vcpu);
@@ -2969,16 +2971,13 @@ static int nested_svm_check_exception(struct vcpu_svm *svm, unsigned nr,
svm->vmcb->control.exit_info_1 = error_code;
/*
- * FIXME: we should not write CR2 when L1 intercepts an L2 #PF exception.
- * The fix is to add the ancillary datum (CR2 or DR6) to structs
- * kvm_queued_exception and kvm_vcpu_events, so that CR2 and DR6 can be
- * written only when inject_pending_event runs (DR6 would written here
- * too). This should be conditional on a new capability---if the
- * capability is disabled, kvm_multiple_exception would write the
- * ancillary information to CR2 or DR6, for backwards ABI-compatibility.
+ * EXITINFO2 is undefined for all exception intercepts other
+ * than #PF.
*/
if (svm->vcpu.arch.exception.nested_apf)
svm->vmcb->control.exit_info_2 = svm->vcpu.arch.apf.nested_apf_token;
+ else if (svm->vcpu.arch.exception.has_payload)
+ svm->vmcb->control.exit_info_2 = svm->vcpu.arch.exception.payload;
else
svm->vmcb->control.exit_info_2 = svm->vcpu.arch.cr2;
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index e665aa7167cf..6d55a2213e12 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3272,27 +3272,24 @@ static int nested_vmx_check_exception(struct kvm_vcpu *vcpu, unsigned long *exit
{
struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
unsigned int nr = vcpu->arch.exception.nr;
+ bool has_payload = vcpu->arch.exception.has_payload;
+ unsigned long payload = vcpu->arch.exception.payload;
if (nr == PF_VECTOR) {
if (vcpu->arch.exception.nested_apf) {
*exit_qual = vcpu->arch.apf.nested_apf_token;
return 1;
}
- /*
- * FIXME: we must not write CR2 when L1 intercepts an L2 #PF exception.
- * The fix is to add the ancillary datum (CR2 or DR6) to structs
- * kvm_queued_exception and kvm_vcpu_events, so that CR2 and DR6
- * can be written only when inject_pending_event runs. This should be
- * conditional on a new capability---if the capability is disabled,
- * kvm_multiple_exception would write the ancillary information to
- * CR2 or DR6, for backwards ABI-compatibility.
- */
if (nested_vmx_is_page_fault_vmexit(vmcs12,
vcpu->arch.exception.error_code)) {
- *exit_qual = vcpu->arch.cr2;
+ *exit_qual = has_payload ? payload : vcpu->arch.cr2;
return 1;
}
} else {
+ /*
+ * FIXME: we must not write DR6 when L1 intercepts an
+ * L2 #DB exception.
+ */
if (vmcs12->exception_bitmap & (1u << nr)) {
if (nr == DB_VECTOR)
*exit_qual = vcpu->arch.dr6;
@@ -3326,6 +3323,8 @@ static void vmx_queue_exception(struct kvm_vcpu *vcpu)
u32 error_code = vcpu->arch.exception.error_code;
u32 intr_info = nr | INTR_INFO_VALID_MASK;
+ kvm_deliver_exception_payload(vcpu);
+
if (has_error_code) {
vmcs_write32(VM_ENTRY_EXCEPTION_ERROR_CODE, error_code);
intr_info |= INTR_INFO_DELIVER_CODE_MASK;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index dcd2cd6351fb..872da22c7514 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -400,6 +400,26 @@ static int exception_type(int vector)
return EXCPT_FAULT;
}
+void kvm_deliver_exception_payload(struct kvm_vcpu *vcpu)
+{
+ unsigned nr = vcpu->arch.exception.nr;
+ bool has_payload = vcpu->arch.exception.has_payload;
+ unsigned long payload = vcpu->arch.exception.payload;
+
+ if (!has_payload)
+ return;
+
+ switch (nr) {
+ case PF_VECTOR:
+ vcpu->arch.cr2 = payload;
+ break;
+ }
+
+ vcpu->arch.exception.has_payload = false;
+ vcpu->arch.exception.payload = 0;
+}
+EXPORT_SYMBOL_GPL(kvm_deliver_exception_payload);
+
static void kvm_multiple_exception(struct kvm_vcpu *vcpu,
unsigned nr, bool has_error, u32 error_code,
bool has_payload, unsigned long payload, bool reinject)
@@ -441,6 +461,18 @@ static void kvm_multiple_exception(struct kvm_vcpu *vcpu,
vcpu->arch.exception.error_code = error_code;
vcpu->arch.exception.has_payload = has_payload;
vcpu->arch.exception.payload = payload;
+ /*
+ * In guest mode, payload delivery should be deferred,
+ * so that the L1 hypervisor can intercept #PF before
+ * CR2 is modified. However, for ABI compatibility
+ * with KVM_GET_VCPU_EVENTS and KVM_SET_VCPU_EVENTS,
+ * we can't delay payload delivery unless userspace
+ * has enabled this functionality via the per-VM
+ * capability, KVM_CAP_EXCEPTION_PAYLOAD.
+ */
+ if (!vcpu->kvm->arch.exception_payload_enabled ||
+ !is_guest_mode(vcpu))
+ kvm_deliver_exception_payload(vcpu);
return;
}
@@ -486,6 +518,13 @@ void kvm_requeue_exception(struct kvm_vcpu *vcpu, unsigned nr)
}
EXPORT_SYMBOL_GPL(kvm_requeue_exception);
+static void kvm_queue_exception_e_p(struct kvm_vcpu *vcpu, unsigned nr,
+ u32 error_code, unsigned long payload)
+{
+ kvm_multiple_exception(vcpu, nr, true, error_code,
+ true, payload, false);
+}
+
int kvm_complete_insn_gp(struct kvm_vcpu *vcpu, int err)
{
if (err)
@@ -502,11 +541,13 @@ void kvm_inject_page_fault(struct kvm_vcpu *vcpu, struct x86_exception *fault)
++vcpu->stat.pf_guest;
vcpu->arch.exception.nested_apf =
is_guest_mode(vcpu) && fault->async_page_fault;
- if (vcpu->arch.exception.nested_apf)
+ if (vcpu->arch.exception.nested_apf) {
vcpu->arch.apf.nested_apf_token = fault->address;
- else
- vcpu->arch.cr2 = fault->address;
- kvm_queue_exception_e(vcpu, PF_VECTOR, fault->error_code);
+ kvm_queue_exception_e(vcpu, PF_VECTOR, fault->error_code);
+ } else {
+ kvm_queue_exception_e_p(vcpu, PF_VECTOR, fault->error_code,
+ fault->address);
+ }
}
EXPORT_SYMBOL_GPL(kvm_inject_page_fault);
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 67b9568613f3..224cd0a47568 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -266,6 +266,8 @@ int kvm_write_guest_virt_system(struct kvm_vcpu *vcpu,
int handle_ud(struct kvm_vcpu *vcpu);
+void kvm_deliver_exception_payload(struct kvm_vcpu *vcpu);
+
void kvm_vcpu_mtrr_init(struct kvm_vcpu *vcpu);
u8 kvm_mtrr_get_guest_memory_type(struct kvm_vcpu *vcpu, gfn_t gfn);
bool kvm_mtrr_valid(struct kvm_vcpu *vcpu, u32 msr, u64 data);
--
2.19.1.331.ge82ca0e54c-goog
