[PATCH 0/3] KVM: x86: Fix goofs with MONITOR/MWAIT quirk

[PATCH 0/3] KVM: x86: Fix goofs with MONITOR/MWAIT quirk

[Sean Christopherson]

Fix two bugs in the MONITOR/MWAIT selftest, and tweak the name of the
quirk (which isn't yet set in stone) to clarify that it only applies to
the #UD behavior, i.e. to reserve the right to correctly emulate #GP and
other faults in the future even if the quirk is enabled.

Sean Christopherson (3):
  KVM: selftests: Test MONITOR and MWAIT, not just MONITOR for quirk
  KVM: selftests: Provide valid inputs for MONITOR/MWAIT regs
  KVM: x86: Tweak name of MONITOR/MWAIT #UD quirk to make it #UD
    specific

 Documentation/virt/kvm/api.rst                         |  2 +-
 arch/x86/include/asm/kvm_host.h                        |  2 +-
 arch/x86/include/uapi/asm/kvm.h                        |  2 +-
 arch/x86/kvm/x86.c                                     |  2 +-
 .../testing/selftests/kvm/x86_64/monitor_mwait_test.c  | 10 +++++++---
 5 files changed, 11 insertions(+), 7 deletions(-)


base-commit: b9b71f43683ae9d76b0989249607bbe8c9eb6c5c
-- 
2.37.0.144.g8ac04bfd2-goog

[PATCH 1/3] KVM: selftests: Test MONITOR and MWAIT, not just MONITOR for quirk

[Sean Christopherson]

Fix a copy+paste error in monitor_mwait_test by switching one of the two
"monitor" instructions to  an "mwait".  The intent of the test is very
much to verify the quirk handles both MONITOR and MWAIT.

Fixes: 2325d4dd7321 ("KVM: selftests: Add MONITOR/MWAIT quirk test")
Reported-by: Yuan Yao <yuan.yao@linux.intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c b/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c
index 49f2ed1c53fe..f5c09cb528ae 100644
--- a/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c
+++ b/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c
@@ -34,7 +34,7 @@ static void guest_monitor_wait(int testcase)
 	else
 		GUEST_ASSERT_2(!vector, testcase, vector);
 
-	vector = kvm_asm_safe("monitor");
+	vector = kvm_asm_safe("mwait");
 	if (fault_wanted)
 		GUEST_ASSERT_2(vector == UD_VECTOR, testcase, vector);
 	else
-- 
2.37.0.144.g8ac04bfd2-goog

[PATCH 2/3] KVM: selftests: Provide valid inputs for MONITOR/MWAIT regs

[Sean Christopherson]

Provide valid inputs for RAX, RCX, and RDX when testing whether or not
KVM injects a #UD on MONITOR/MWAIT.  SVM has a virtualization hole and
checks for _all_ faults before checking for intercepts, e.g. MONITOR with
an unsupported RCX will #GP before KVM gets a chance to intercept and
emulate.

Fixes: 2325d4dd7321 ("KVM: selftests: Add MONITOR/MWAIT quirk test")
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c b/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c
index f5c09cb528ae..6a4ebcdfa374 100644
--- a/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c
+++ b/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c
@@ -28,13 +28,17 @@ static void guest_monitor_wait(int testcase)
 
 	GUEST_SYNC(testcase);
 
-	vector = kvm_asm_safe("monitor");
+	/*
+	 * Arbitrarily MONITOR this function, SVM performs fault checks before
+	 * intercept checks, so the inputs for MONITOR and MWAIT must be valid.
+	 */
+	vector = kvm_asm_safe("monitor", "a"(guest_monitor_wait), "c"(0), "d"(0));
 	if (fault_wanted)
 		GUEST_ASSERT_2(vector == UD_VECTOR, testcase, vector);
 	else
 		GUEST_ASSERT_2(!vector, testcase, vector);
 
-	vector = kvm_asm_safe("mwait");
+	vector = kvm_asm_safe("mwait", "a"(guest_monitor_wait), "c"(0), "d"(0));
 	if (fault_wanted)
 		GUEST_ASSERT_2(vector == UD_VECTOR, testcase, vector);
 	else
-- 
2.37.0.144.g8ac04bfd2-goog

[PATCH 3/3] KVM: x86: Tweak name of MONITOR/MWAIT #UD quirk to make it #UD specific

[Sean Christopherson]

Add a "UD" clause to KVM_X86_QUIRK_MWAIT_NEVER_FAULTS to make it clear
that the quirk only controls the #UD behavior of MONITOR/MWAIT.  KVM
doesn't currently enforce fault checks when MONITOR/MWAIT are supported,
but that could change in the future.  SVM also has a virtualization hole
in that it checks all faults before intercepts, and so "never faults" is
already a lie when running on SVM.

Fixes: bfbcc81bb82c ("KVM: x86: Add a quirk for KVM's "MONITOR/MWAIT are NOPs!" behavior")
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 Documentation/virt/kvm/api.rst                          | 2 +-
 arch/x86/include/asm/kvm_host.h                         | 2 +-
 arch/x86/include/uapi/asm/kvm.h                         | 2 +-
 arch/x86/kvm/x86.c                                      | 2 +-
 tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c | 2 +-
 5 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index bafaeedd455c..cd9361f22530 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -7523,7 +7523,7 @@ The valid bits in cap.args[0] are:
                                     incorrect hypercall instruction will
                                     generate a #UD within the guest.
 
-KVM_X86_QUIRK_MWAIT_NEVER_FAULTS    By default, KVM emulates MONITOR/MWAIT (if
+KVM_X86_QUIRK_MWAIT_NEVER_UD_FAULTS By default, KVM emulates MONITOR/MWAIT (if
                                     they are intercepted) as NOPs regardless of
                                     whether or not MONITOR/MWAIT are supported
                                     according to guest CPUID.  When this quirk
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index de5a149d0971..b9e85049743f 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -2097,6 +2097,6 @@ int memslot_rmap_alloc(struct kvm_memory_slot *slot, unsigned long npages);
 	 KVM_X86_QUIRK_OUT_7E_INC_RIP |		\
 	 KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT |	\
 	 KVM_X86_QUIRK_FIX_HYPERCALL_INSN |	\
-	 KVM_X86_QUIRK_MWAIT_NEVER_FAULTS)
+	 KVM_X86_QUIRK_MWAIT_NEVER_UD_FAULTS)
 
 #endif /* _ASM_X86_KVM_HOST_H */
diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index ee3896416c68..a0c0ab0c898e 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -439,7 +439,7 @@ struct kvm_sync_regs {
 #define KVM_X86_QUIRK_OUT_7E_INC_RIP		(1 << 3)
 #define KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT	(1 << 4)
 #define KVM_X86_QUIRK_FIX_HYPERCALL_INSN	(1 << 5)
-#define KVM_X86_QUIRK_MWAIT_NEVER_FAULTS	(1 << 6)
+#define KVM_X86_QUIRK_MWAIT_NEVER_UD_FAULTS	(1 << 6)
 
 #define KVM_STATE_NESTED_FORMAT_VMX	0
 #define KVM_STATE_NESTED_FORMAT_SVM	1
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 567d13405445..8065998c5bb6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2046,7 +2046,7 @@ EXPORT_SYMBOL_GPL(kvm_handle_invalid_op);
 
 static int kvm_emulate_monitor_mwait(struct kvm_vcpu *vcpu, const char *insn)
 {
-	if (!kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_MWAIT_NEVER_FAULTS) &&
+	if (!kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_MWAIT_NEVER_UD_FAULTS) &&
 	    !guest_cpuid_has(vcpu, X86_FEATURE_MWAIT))
 		return kvm_handle_invalid_op(vcpu);
 
diff --git a/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c b/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c
index 6a4ebcdfa374..094c68d744c0 100644
--- a/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c
+++ b/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c
@@ -113,7 +113,7 @@ int main(int argc, char *argv[])
 
 		disabled_quirks = 0;
 		if (testcase & MWAIT_QUIRK_DISABLED)
-			disabled_quirks |= KVM_X86_QUIRK_MWAIT_NEVER_FAULTS;
+			disabled_quirks |= KVM_X86_QUIRK_MWAIT_NEVER_UD_FAULTS;
 		if (testcase & MISC_ENABLES_QUIRK_DISABLED)
 			disabled_quirks |= KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT;
 		vm_enable_cap(vm, KVM_CAP_DISABLE_QUIRKS2, disabled_quirks);
-- 
2.37.0.144.g8ac04bfd2-goog