Override vcpu_arch_put_guest() to randomly force emulation on supported
accesses. Force emulation of LOCK CMPXCHG as well as a regular MOV to
stress KVM's emulation of atomic accesses, which has a unique path in
KVM's emulator.
Arbitrarily give all the decisions 50/50 odds; absent much, much more
sophisticated infrastructure for generating random numbers, it's highly
unlikely that doing more than a coin flip with affect selftests' ability
to find KVM bugs.
This is effectively a regression test for commit 910c57dfa4d1 ("KVM: x86:
Mark target gfn of emulated atomic instruction as dirty").
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
.../kvm/include/x86_64/kvm_util_arch.h | 21 +++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/tools/testing/selftests/kvm/include/x86_64/kvm_util_arch.h b/tools/testing/selftests/kvm/include/x86_64/kvm_util_arch.h
index 41aba476640a..d0b587c38e07 100644
--- a/tools/testing/selftests/kvm/include/x86_64/kvm_util_arch.h
+++ b/tools/testing/selftests/kvm/include/x86_64/kvm_util_arch.h
@@ -5,6 +5,8 @@
#include <stdbool.h>
#include <stdint.h>
+#include "test_util.h"
+
extern bool is_forced_emulation_enabled;
struct kvm_vm_arch {
@@ -22,4 +24,23 @@ static inline bool __vm_arch_has_protected_memory(struct kvm_vm_arch *arch)
#define vm_arch_has_protected_memory(vm) \
__vm_arch_has_protected_memory(&(vm)->arch)
+#define vcpu_arch_put_guest(mem, __val) \
+do { \
+ const typeof(mem) val = (__val); \
+ \
+ if (!is_forced_emulation_enabled || guest_random_bool(&guest_rng)) { \
+ (mem) = val; \
+ } else if (guest_random_bool(&guest_rng)) { \
+ __asm__ __volatile__(KVM_FEP "mov %1, %0" \
+ : "+m" (mem) \
+ : "r" (val) : "memory"); \
+ } else { \
+ uint64_t __old = READ_ONCE(mem); \
+ \
+ __asm__ __volatile__(KVM_FEP LOCK_PREFIX "cmpxchg %[new], %[ptr]" \
+ : [ptr] "+m" (mem), [old] "+a" (__old) \
+ : [new]"r" (val) : "memory", "cc"); \
+ } \
+} while (0)
+
#endif // SELFTEST_KVM_UTIL_ARCH_H
--
2.44.0.291.gc1ea87d7ee-goog
