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Commit 204c91ef authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

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: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 12e9612c

tools/testing/selftests/kvm/x86_64/sync_regs_test.c

+30 −24
Original line number Diff line number Diff line
@@ -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);