From 204c91eff798a78498cc7cbf1bc76892badfa96d Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Mon, 20 May 2019 13:31:02 +0200 Subject: 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 --- .../testing/selftests/kvm/x86_64/sync_regs_test.c | 54 ++++++++++++---------- 1 file changed, 30 insertions(+), 24 deletions(-) (limited to 'tools/testing/selftests') 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, ®s); 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, ®s); - 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, ®s); - 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); -- cgit v1.2.3-59-g8ed1b