[PATCH v2 3/6] KVM: VMX: Handle vectoring error in check_emulate_instruction

Ivan Orlov
2024-11-11T10:28:10Z

Move unhandleable vmexit due to MMIO during vectoring error detection
into check_emulate_instruction. Implement a function which checks if
emul_type indicates MMIO so it can be used for both VMX and SVM.

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.

Signed-off-by: Ivan Orlov <iorlov@amazon.com>
---
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)

arch/x86/include/asm/kvm_host.h | 10 ++++++++--
arch/x86/kvm/vmx/vmx.c | 25 ++++++++++++-------------
2 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index eb413079b7c6..3de9702a9135 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -2017,8 +2017,8 @@ 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
@@ -2053,6 +2053,12 @@ 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_is_emul_type_mmio(int emul_type)
+{
+ return (emul_type & EMULTYPE_PF) &&
+ !(emul_type & EMULTYPE_WRITE_PF_TO_SP);
+}
+
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 f92740e7e107..a10f35d9704b 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1693,6 +1693,8 @@ static int vmx_rtit_ctl_check(struct kvm_vcpu *vcpu, u64 data)
int vmx_check_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
void *insn, int insn_len)
{
+ bool is_vect;
+
/*
* Emulation of instructions in SGX enclaves is impossible as RIP does
* not point at the failing instruction, and even if it did, the code
@@ -1704,6 +1706,13 @@ int vmx_check_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
kvm_queue_exception(vcpu, UD_VECTOR);
return X86EMUL_PROPAGATE_FAULT;
}
+
+ is_vect = to_vmx(vcpu)->idt_vectoring_info & VECTORING_INFO_VALID_MASK;
+
+ /* Emulation is not possible when MMIO happens during event vectoring. */
+ if (kvm_is_emul_type_mmio(emul_type) && is_vect)
+ return X86EMUL_UNHANDLEABLE_VECTORING_IO;
+
return X86EMUL_CONTINUE;
}

@@ -6452,7 +6461,6 @@ static int __vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
union vmx_exit_reason exit_reason = vmx->exit_reason;
u32 vectoring_info = vmx->idt_vectoring_info;
u16 exit_handler_index;
- gpa_t gpa;

/*
* Flush logged GPAs PML buffer, this will make dirty_bitmap more
@@ -6537,24 +6545,15 @@ 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 = exit_reason.basic == EXIT_REASON_EPT_MISCONFIG
- ? vmcs_read64(GUEST_PHYSICAL_ADDRESS) : INVALID_GPA;
-
- 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