Move unhandleable vmexit during vectoring error detection
into check_emulate_instruction. Implement the function which prohibits
the emulation if EMULTYPE_PF is set when vectoring, otherwise such a
situation may occur:
1. CPU executes an instruction and hits a #GP
2. While vectoring the #GP, a shadow #PF occurs
3. On vmexit, KVM re-injects #GP
4. KVM emulates because of the write-protected page
5. KVM "successfully" emulates and also detects the #GP
6. KVM synthesizes a #GP, and since #GP has already been injected,
incorrectly escalates to a #DF.
Fix the comment about EMULTYPE_PF as this flag doesn't necessarily
mean MMIO anymore: it can also be set due to the write protection
violation.
Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Ivan Orlov <iorlov@xxxxxxxxxx>
---
V1 -> V2:
- Detect the unhandleable vectoring error in vmx_check_emulate_instruction
instead of handling it in the common MMU code (which is specific for
cached MMIO)
V2 -> V3:
- Prohibit any emulation during vectoring if it happens due to an
intercepted #PF.
arch/x86/include/asm/kvm_host.h | 9 +++++++--
arch/x86/kvm/vmx/vmx.c | 23 +++++++++--------------
2 files changed, 16 insertions(+), 16 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index de8fb1ab230c..f3a1d050e1d6 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -2019,8 +2019,8 @@ u64 vcpu_tsc_khz(struct kvm_vcpu *vcpu);
* VMware backdoor emulation handles select instructions
* and reinjects the #GP for all other cases.
*
- * EMULTYPE_PF - Set when emulating MMIO by way of an intercepted #PF, in which
- * case the CR2/GPA value pass on the stack is valid.
+ * EMULTYPE_PF - Set when an intercepted #PF triggers the emulation, in which case
+ * the CR2/GPA value pass on the stack is valid.
*
* EMULTYPE_COMPLETE_USER_EXIT - Set when the emulator should update interruptibility
* state and inject single-step #DBs after skipping
@@ -2055,6 +2055,11 @@ u64 vcpu_tsc_khz(struct kvm_vcpu *vcpu);
#define EMULTYPE_COMPLETE_USER_EXIT (1 << 7)
#define EMULTYPE_WRITE_PF_TO_SP (1 << 8)
+static inline bool kvm_can_emulate_event_vectoring(int emul_type)
+{
+ return !(emul_type & EMULTYPE_PF);
+}
+
int kvm_emulate_instruction(struct kvm_vcpu *vcpu, int emulation_type);
int kvm_emulate_instruction_from_buffer(struct kvm_vcpu *vcpu,
void *insn, int insn_len);
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index acc2f0e0a339..89ddbe1175c7 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1705,6 +1705,12 @@ int vmx_check_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
kvm_queue_exception(vcpu, UD_VECTOR);
return X86EMUL_PROPAGATE_FAULT;
}
+
+ /* Check that emulation is possible during event vectoring */
+ if ((to_vmx(vcpu)->idt_vectoring_info & VECTORING_INFO_VALID_MASK) &&
+ !kvm_can_emulate_event_vectoring(emul_type))
+ return X86EMUL_UNHANDLEABLE_VECTORING;
+
return X86EMUL_CONTINUE;
}
@@ -6543,26 +6549,15 @@ static int __vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
return 0;
}
- /*
- * Note:
- * Do not try to fix EXIT_REASON_EPT_MISCONFIG if it caused by
- * delivery event since it indicates guest is accessing MMIO.
- * The vm-exit can be triggered again after return to guest that
- * will cause infinite loop.
- */
if ((vectoring_info & VECTORING_INFO_VALID_MASK) &&
(exit_reason.basic != EXIT_REASON_EXCEPTION_NMI &&
exit_reason.basic != EXIT_REASON_EPT_VIOLATION &&
exit_reason.basic != EXIT_REASON_PML_FULL &&
exit_reason.basic != EXIT_REASON_APIC_ACCESS &&
exit_reason.basic != EXIT_REASON_TASK_SWITCH &&
- exit_reason.basic != EXIT_REASON_NOTIFY)) {
- gpa_t gpa = INVALID_GPA;
-
- if (exit_reason.basic == EXIT_REASON_EPT_MISCONFIG)
- gpa = vmcs_read64(GUEST_PHYSICAL_ADDRESS);
-
- kvm_prepare_event_vectoring_exit(vcpu, gpa);
+ exit_reason.basic != EXIT_REASON_NOTIFY &&
+ exit_reason.basic != EXIT_REASON_EPT_MISCONFIG)) {
+ kvm_prepare_event_vectoring_exit(vcpu, INVALID_GPA);
return 0;
}
--
2.43.0
