KVM: selftests: Verify SEV+ guests can read and write EFER, CR0, CR4, and CR8

Add "do no harm" testing of EFER, CR0, CR4, and CR8 for SEV+ guests to
verify that the guest can read and write the registers, without hitting
e.g. a #VC on SEV-ES guests due to KVM incorrectly trying to intercept a
register.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260310211841.2552361-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/tools/testing/selftests/kvm/include/x86/processor.h b/tools/testing/selftests/kvm/include/x86/processor.h
index 4ebae4269e68..469a22122157 100644
--- a/tools/testing/selftests/kvm/include/x86/processor.h
+++ b/tools/testing/selftests/kvm/include/x86/processor.h
@@ -557,6 +557,11 @@ static inline uint64_t get_cr0(void)
 	return cr0;
 }
 
+static inline void set_cr0(uint64_t val)
+{
+	__asm__ __volatile__("mov %0, %%cr0" : : "r" (val) : "memory");
+}
+
 static inline uint64_t get_cr3(void)
 {
 	uint64_t cr3;
@@ -566,6 +571,11 @@ static inline uint64_t get_cr3(void)
 	return cr3;
 }
 
+static inline void set_cr3(uint64_t val)
+{
+	__asm__ __volatile__("mov %0, %%cr3" : : "r" (val) : "memory");
+}
+
 static inline uint64_t get_cr4(void)
 {
 	uint64_t cr4;
@@ -580,6 +590,19 @@ static inline void set_cr4(uint64_t val)
 	__asm__ __volatile__("mov %0, %%cr4" : : "r" (val) : "memory");
 }
 
+static inline uint64_t get_cr8(void)
+{
+	uint64_t cr8;
+
+	__asm__ __volatile__("mov %%cr8, %[cr8]" : [cr8]"=r"(cr8));
+	return cr8;
+}
+
+static inline void set_cr8(uint64_t val)
+{
+	__asm__ __volatile__("mov %0, %%cr8" : : "r" (val) : "memory");
+}
+
 static inline void set_idt(const struct desc_ptr *idt_desc)
 {
 	__asm__ __volatile__("lidt %0"::"m"(*idt_desc));