Re: [PATCH v1 3/3] KVM: selftests: Add a test case for KVM_X86_DISABLE_EXITS_HLT

[Muhammad Usama Anjum <usama.anjum@collabora.com>]

On 4/1/24 10:28 AM, Manali Shukla wrote:
> Hi Muhammad Usama Anjum,
> 
> Thank you for reviewing my patch.
> 
> On 3/30/2024 1:43 AM, Muhammad Usama Anjum wrote:
>> On 3/27/24 10:42 AM, Manali Shukla wrote:
>>> By default, HLT instruction executed by guest is intercepted by hypervisor.
>>> However, KVM_CAP_X86_DISABLE_EXITS capability can be used to not intercept
>>> HLT by setting KVM_X86_DISABLE_EXITS_HLT.
>>>
>>> Add a test case to test KVM_X86_DISABLE_EXITS_HLT functionality.
>>>
>>> Suggested-by: Sean Christopherson <seanjc@google.com>
>>> Signed-off-by: Manali Shukla <manali.shukla@amd.com>
>> Thank you for the new test patch. We have been trying to ensure TAP
>> conformance for tests which cannot be achieved if new tests aren't using
>> TAP already. Please make your test TAP compliant.
> 
> As per my understanding about TAP interface, kvm_test_harness.h file includes a MACRO,
> which is used to create VM with one vcpu using vm_create_with_one_vcpu(), but
> halt_disable_exit_test creates a customized VM with KVM_CAP_X86_DISABLE_EXITS
> capability set and different vm_shape parameters to start a VM without in-kernel
> APIC support. AFAIU, I won't be able to use KVM_ONE_VCPU_TEST_SUITE MACRO as is.
> How do you suggest to proceed with this issue? 
TAP interface is just a way to print logs which are machine readable for
CIs. So log messages, test pass or fail should be marked by
tools/testing/selftests/kselftest.h or
tools/testing/selftests/kselftest_harness.h. It depends on the design of
your test that which would be suitable.

It seems that most tests in KVM suite aren't TAP compliant. In this case,
I'm okay with non-TAP compliant test as the whole suite is far from compliance.

> 
>>
>>> ---
>>>  tools/testing/selftests/kvm/Makefile          |   1 +
>>>  .../kvm/x86_64/halt_disable_exit_test.c       | 113 ++++++++++++++++++
>> Add generated object to .gitignore file.
> 
> Sure. I will do it.
>>
>>>  2 files changed, 114 insertions(+)
>>>  create mode 100644 tools/testing/selftests/kvm/x86_64/halt_disable_exit_test.c
>>>
>>> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
>>> index c75251d5c97c..9f72abb95d2e 100644
>>> --- a/tools/testing/selftests/kvm/Makefile
>>> +++ b/tools/testing/selftests/kvm/Makefile
>>> @@ -89,6 +89,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/set_sregs_test
>>>  TEST_GEN_PROGS_x86_64 += x86_64/smaller_maxphyaddr_emulation_test
>>>  TEST_GEN_PROGS_x86_64 += x86_64/smm_test
>>>  TEST_GEN_PROGS_x86_64 += x86_64/state_test
>>> +TEST_GEN_PROGS_x86_64 += x86_64/halt_disable_exit_test
>>>  TEST_GEN_PROGS_x86_64 += x86_64/vmx_preemption_timer_test
>>>  TEST_GEN_PROGS_x86_64 += x86_64/svm_vmcall_test
>>>  TEST_GEN_PROGS_x86_64 += x86_64/svm_int_ctl_test
>>> diff --git a/tools/testing/selftests/kvm/x86_64/halt_disable_exit_test.c b/tools/testing/selftests/kvm/x86_64/halt_disable_exit_test.c
>>> new file mode 100644
>>> index 000000000000..b7279dd0eaff
>>> --- /dev/null
>>> +++ b/tools/testing/selftests/kvm/x86_64/halt_disable_exit_test.c
>>> @@ -0,0 +1,113 @@
>>> +// SPDX-License-Identifier: GPL-2.0-only
>>> +/*
>>> + * KVM disable halt exit test
>>> + *
>>> + *  Copyright (C) 2024 Advanced Micro Devices, Inc.
>>> + */
>>> +#include <pthread.h>
>>> +#include <signal.h>
>>> +#include "kvm_util.h"
>>> +#include "svm_util.h"
>>> +#include "processor.h"
>>> +#include "test_util.h"
>>> +
>>> +pthread_t task_thread, vcpu_thread;
>>> +#define SIG_IPI SIGUSR1
>>> +
>>> +static void guest_code(uint8_t is_hlt_exec)
>>> +{
>>> +	while (!READ_ONCE(is_hlt_exec))
>>> +		;
>>> +
>>> +	safe_halt();
>>> +	GUEST_DONE();
>>> +}
>>> +
>>> +static void *task_worker(void *arg)
>>> +{
>>> +	uint8_t *is_hlt_exec = (uint8_t *)arg;
>>> +
>>> +	usleep(1000);
>>> +	WRITE_ONCE(*is_hlt_exec, 1);
>>> +	pthread_kill(vcpu_thread, SIG_IPI);
>>> +	return 0;
>>> +}
>>> +
>>> +static void *vcpu_worker(void *arg)
>>> +{
>>> +	int ret;
>>> +	int sig = -1;
>>> +	uint8_t *is_hlt_exec = (uint8_t *)arg;
>>> +	struct kvm_vm *vm;
>>> +	struct kvm_run *run;
>>> +	struct kvm_vcpu *vcpu;
>>> +	struct kvm_signal_mask *sigmask = alloca(offsetof(struct kvm_signal_mask, sigset)
>>> +						 + sizeof(sigset_t));
>>> +	sigset_t *sigset = (sigset_t *) &sigmask->sigset;
>>> +
>>> +	/* Create a VM without in kernel APIC support */
>>> +	vm = __vm_create(VM_SHAPE_DEFAULT, 1, 0, false);
>>> +	vm_enable_cap(vm, KVM_CAP_X86_DISABLE_EXITS, KVM_X86_DISABLE_EXITS_HLT);
>>> +	vcpu = vm_vcpu_add(vm, 0, guest_code);
>>> +	vcpu_args_set(vcpu, 1, *is_hlt_exec);
>>> +
>>> +	/*
>>> +	 * SIG_IPI is unblocked atomically while in KVM_RUN.  It causes the
>>> +	 * ioctl to return with -EINTR, but it is still pending and we need
>>> +	 * to accept it with the sigwait.
>>> +	 */
>>> +	sigmask->len = 8;
>>> +	pthread_sigmask(0, NULL, sigset);
>>> +	sigdelset(sigset, SIG_IPI);
>>> +	vcpu_ioctl(vcpu, KVM_SET_SIGNAL_MASK, sigmask);
>>> +	sigemptyset(sigset);
>>> +	sigaddset(sigset, SIG_IPI);
>>> +	run = vcpu->run;
>>> +
>>> +again:
>>> +	ret = __vcpu_run(vcpu);
>>> +	TEST_ASSERT_EQ(errno, EINTR);
>>> +
>>> +	if (ret == -1 && errno == EINTR) {
>>> +		sigwait(sigset, &sig);
>>> +		assert(sig == SIG_IPI);
>>> +		TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_INTR);
>>> +		goto again;
>>> +	}
>>> +
>>> +	if (run->exit_reason == KVM_EXIT_HLT)
>>> +		TEST_FAIL("Expected KVM_EXIT_INTR, got KVM_EXIT_HLT");
>>> +
>>> +	TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
>>> +	kvm_vm_free(vm);
>>> +	return 0;
>>> +}
>>> +
>>> +int main(int argc, char *argv[])
>>> +{
>>> +	int ret;
>>> +	void *retval;
>>> +	uint8_t is_halt_exec;
>>> +	sigset_t sigset;
>>> +
>>> +	TEST_REQUIRE(kvm_has_cap(KVM_CAP_X86_DISABLE_EXITS));
>>> +
>>> +	/* Ensure that vCPU threads start with SIG_IPI blocked.  */
>>> +	sigemptyset(&sigset);
>>> +	sigaddset(&sigset, SIG_IPI);
>>> +	pthread_sigmask(SIG_BLOCK, &sigset, NULL);
>>> +
>>> +	ret = pthread_create(&vcpu_thread, NULL, vcpu_worker, &is_halt_exec);
>>> +	TEST_ASSERT(ret == 0, "pthread_create vcpu thread failed errno=%d", errno);
>>> +
>>> +	ret = pthread_create(&task_thread, NULL, task_worker, &is_halt_exec);
>>> +	TEST_ASSERT(ret == 0, "pthread_create task thread failed errno=%d", errno);
>>> +
>>> +	pthread_join(vcpu_thread, &retval);
>>> +	TEST_ASSERT(ret == 0, "pthread_join on vcpu thread failed with errno=%d", ret);
>>> +
>>> +	pthread_join(task_thread, &retval);
>>> +	TEST_ASSERT(ret == 0, "pthread_join on task thread failed with errno=%d", ret);
>>> +
>>> +	return 0;
>>> +}
>>
> - Manali
> 

-- 
BR,
Muhammad Usama Anjum