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authorPaolo Bonzini <pbonzini@redhat.com>2019-05-20 13:31:02 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2019-05-24 21:27:10 +0200
commit204c91eff798a78498cc7cbf1bc76892badfa96d (patch)
treecd9516683048d89eaba676657df4ac615b86c52c
parent12e9612cae0c272e0dabfc570a6d855f07361914 (diff)
downloadlinux-stericsson-204c91eff798a78498cc7cbf1bc76892badfa96d.tar.gz
KVM: selftests: do not blindly clobber registers in guest asm
The guest_code of sync_regs_test is assuming that the compiler will not touch %r11 outside the asm that increments it, which is a bit brittle. Instead, we can increment a variable and use a dummy asm to ensure the increment is not optimized away. However, we also need to use a callee-save register or the compiler will insert a save/restore around the vmexit, breaking the whole idea behind the test. (Yes, "if it ain't broken...", but I would like the test to be clean before it is copied into the upcoming s390 selftests). Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--tools/testing/selftests/kvm/x86_64/sync_regs_test.c54
1 files changed, 30 insertions, 24 deletions
diff --git a/tools/testing/selftests/kvm/x86_64/sync_regs_test.c b/tools/testing/selftests/kvm/x86_64/sync_regs_test.c
index c8478ce9ea77..25cacd3316f6 100644
--- a/tools/testing/selftests/kvm/x86_64/sync_regs_test.c
+++ b/tools/testing/selftests/kvm/x86_64/sync_regs_test.c
@@ -25,9 +25,15 @@
void guest_code(void)
{
+ /*
+ * use a callee-save register, otherwise the compiler
+ * saves it around the call to GUEST_SYNC.
+ */
+ register u32 stage asm("rbx");
for (;;) {
GUEST_SYNC(0);
- asm volatile ("inc %r11");
+ stage++;
+ asm volatile ("" : : "r" (stage));
}
}
@@ -147,7 +153,7 @@ int main(int argc, char *argv[])
compare_vcpu_events(&events, &run->s.regs.events);
/* Set and verify various register values. */
- run->s.regs.regs.r11 = 0xBAD1DEA;
+ run->s.regs.regs.rbx = 0xBAD1DEA;
run->s.regs.sregs.apic_base = 1 << 11;
/* TODO run->s.regs.events.XYZ = ABC; */
@@ -158,9 +164,9 @@ int main(int argc, char *argv[])
"Unexpected exit reason: %u (%s),\n",
run->exit_reason,
exit_reason_str(run->exit_reason));
- TEST_ASSERT(run->s.regs.regs.r11 == 0xBAD1DEA + 1,
- "r11 sync regs value incorrect 0x%llx.",
- run->s.regs.regs.r11);
+ TEST_ASSERT(run->s.regs.regs.rbx == 0xBAD1DEA + 1,
+ "rbx sync regs value incorrect 0x%llx.",
+ run->s.regs.regs.rbx);
TEST_ASSERT(run->s.regs.sregs.apic_base == 1 << 11,
"apic_base sync regs value incorrect 0x%llx.",
run->s.regs.sregs.apic_base);
@@ -179,15 +185,15 @@ int main(int argc, char *argv[])
*/
run->kvm_valid_regs = TEST_SYNC_FIELDS;
run->kvm_dirty_regs = 0;
- run->s.regs.regs.r11 = 0xDEADBEEF;
+ run->s.regs.regs.rbx = 0xDEADBEEF;
rv = _vcpu_run(vm, VCPU_ID);
TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
"Unexpected exit reason: %u (%s),\n",
run->exit_reason,
exit_reason_str(run->exit_reason));
- TEST_ASSERT(run->s.regs.regs.r11 != 0xDEADBEEF,
- "r11 sync regs value incorrect 0x%llx.",
- run->s.regs.regs.r11);
+ TEST_ASSERT(run->s.regs.regs.rbx != 0xDEADBEEF,
+ "rbx sync regs value incorrect 0x%llx.",
+ run->s.regs.regs.rbx);
/* Clear kvm_valid_regs bits and kvm_dirty_bits.
* Verify s.regs values are not overwritten with existing guest values
@@ -195,21 +201,21 @@ int main(int argc, char *argv[])
*/
run->kvm_valid_regs = 0;
run->kvm_dirty_regs = 0;
- run->s.regs.regs.r11 = 0xAAAA;
- regs.r11 = 0xBAC0;
+ run->s.regs.regs.rbx = 0xAAAA;
+ regs.rbx = 0xBAC0;
vcpu_regs_set(vm, VCPU_ID, &regs);
rv = _vcpu_run(vm, VCPU_ID);
TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
"Unexpected exit reason: %u (%s),\n",
run->exit_reason,
exit_reason_str(run->exit_reason));
- TEST_ASSERT(run->s.regs.regs.r11 == 0xAAAA,
- "r11 sync regs value incorrect 0x%llx.",
- run->s.regs.regs.r11);
+ TEST_ASSERT(run->s.regs.regs.rbx == 0xAAAA,
+ "rbx sync regs value incorrect 0x%llx.",
+ run->s.regs.regs.rbx);
vcpu_regs_get(vm, VCPU_ID, &regs);
- TEST_ASSERT(regs.r11 == 0xBAC0 + 1,
- "r11 guest value incorrect 0x%llx.",
- regs.r11);
+ TEST_ASSERT(regs.rbx == 0xBAC0 + 1,
+ "rbx guest value incorrect 0x%llx.",
+ regs.rbx);
/* Clear kvm_valid_regs bits. Verify s.regs values are not overwritten
* with existing guest values but that guest values are overwritten
@@ -217,19 +223,19 @@ int main(int argc, char *argv[])
*/
run->kvm_valid_regs = 0;
run->kvm_dirty_regs = TEST_SYNC_FIELDS;
- run->s.regs.regs.r11 = 0xBBBB;
+ run->s.regs.regs.rbx = 0xBBBB;
rv = _vcpu_run(vm, VCPU_ID);
TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
"Unexpected exit reason: %u (%s),\n",
run->exit_reason,
exit_reason_str(run->exit_reason));
- TEST_ASSERT(run->s.regs.regs.r11 == 0xBBBB,
- "r11 sync regs value incorrect 0x%llx.",
- run->s.regs.regs.r11);
+ TEST_ASSERT(run->s.regs.regs.rbx == 0xBBBB,
+ "rbx sync regs value incorrect 0x%llx.",
+ run->s.regs.regs.rbx);
vcpu_regs_get(vm, VCPU_ID, &regs);
- TEST_ASSERT(regs.r11 == 0xBBBB + 1,
- "r11 guest value incorrect 0x%llx.",
- regs.r11);
+ TEST_ASSERT(regs.rbx == 0xBBBB + 1,
+ "rbx guest value incorrect 0x%llx.",
+ regs.rbx);
kvm_vm_free(vm);