linux-kernel - Re: [V4 8/8] KVM: selftests: Add simple sev vm testing

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Message-ID: <Yz8e9t0L//pXD9S9@google.com>
Date:   Thu, 6 Oct 2022 18:31:18 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Peter Gonda <pgonda@...gle.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        marcorr@...gle.com, michael.roth@....com, thomas.lendacky@....com,
        joro@...tes.org, mizhang@...gle.com, pbonzini@...hat.com,
        andrew.jones@...ux.dev
Subject: Re: [V4 8/8] KVM: selftests: Add simple sev vm testing

On Mon, Aug 29, 2022, Peter Gonda wrote:
> +	for (i = 0; i <= NR_SYNCS; ++i) {
> +		vcpu_run(vcpu);
> +		switch (get_ucall(vcpu, &uc)) {
> +		case UCALL_SYNC:
> +			continue;
> +		case UCALL_DONE:
> +			return;
> +		case UCALL_ABORT:
> +			TEST_ASSERT(false, "%s at %s:%ld\n\tvalues: %#lx, %#lx",
> +				    (const char *)uc.args[0], __FILE__,
> +				    uc.args[1], uc.args[2], uc.args[3]);

REPORT_GUEST_ASSERT

> +		default:
> +			TEST_ASSERT(
> +				false, "Unexpected exit: %s",
> +				exit_reason_str(vcpu->run->exit_reason));

TEST_FAIL

> +		}
> +	}
> +}
> +
> +static void guest_sev_code(void)
> +{
> +	uint32_t eax, ebx, ecx, edx;
> +	uint64_t sev_status;
> +
> +	GUEST_SYNC(1);
> +
> +	GUEST_ASSERT(this_cpu_has(X86_FEATURE_SEV));
> +
> +	sev_status = rdmsr(MSR_AMD64_SEV);
> +	GUEST_ASSERT((sev_status & 0x1) == 1);

Add a #define for the magic 0x1.  And the "== 1" is unnecessary.  Hmm, and the
querying of SEV/SEV-ES/etc status in MSR_AMD64_SEV should be done in helpers.

> +
> +	GUEST_DONE();
> +}
> +
> +static struct sev_vm *setup_test_common(void *guest_code, uint64_t policy,
> +					struct kvm_vcpu **vcpu)
> +{
> +	uint8_t measurement[512];
> +	struct sev_vm *sev;
> +	struct kvm_vm *vm;
> +	int i;
> +
> +	sev = sev_vm_create(policy, TOTAL_PAGES);
> +	TEST_ASSERT(sev, "sev_vm_create() failed to create VM\n");

See earlier comments on using TEST_REQUIRE.

> +
> +	vm = sev->vm;
> +
> +	/* Set up VCPU and initial guest kernel. */
> +	*vcpu = vm_vcpu_add(vm, 0, guest_code);
> +	kvm_vm_elf_load(vm, program_invocation_name);
> +
> +	/* Allocations/setup done. Encrypt initial guest payload. */
> +	sev_vm_launch(sev);
> +
> +	/* Dump the initial measurement. A test to actually verify it would be nice. */
> +	sev_vm_launch_measure(sev, measurement);
> +	pr_info("guest measurement: ");
> +	for (i = 0; i < 32; ++i)
> +		pr_info("%02x", measurement[i]);
> +	pr_info("\n");
> +
> +	sev_vm_launch_finish(sev);

I believe this entire function gets replaced with

	vm = ____vm_create_with_one_vcpu(VM_MODE_PXXV48_4K_SEV, &vcpu, 0,
					 guest_code);

> +
> +	return sev;
> +}
> +
> +static void test_sev(void *guest_code, uint64_t policy)
> +{
> +	struct sev_vm *sev;
> +	struct kvm_vcpu *vcpu;
> +
> +	sev = setup_test_common(guest_code, policy, &vcpu);
> +
> +	/* Guest is ready to run. Do the tests. */

Comment doesn't add much value.

> +	guest_run_loop(vcpu);
> +
> +	pr_info("guest ran successfully\n");

Meh, the test passing is a good indication the test ran successfully.

> +
> +	sev_vm_free(sev);
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +	/* SEV tests */

Again, stating the obvious.

> +	test_sev(guest_sev_code, SEV_POLICY_NO_DBG);
> +	test_sev(guest_sev_code, 0);
> +
> +	return 0;
> +}
> -- 
> 2.37.2.672.g94769d06f0-goog
>