Re: [PATCH v3 3/3] KVM: selftests: Test behavior of HWCR

[Sean Christopherson <seanjc@google.com>]

On Thu, Sep 28, 2023, Jim Mattson wrote:
> Verify the following:
> * Attempts to set bits 3, 6, or 8 are ignored
> * Bits 18 and 24 are the only bits that can be set
> * Any bit that can be set can also be cleared
> 
> Signed-off-by: Jim Mattson <jmattson@google.com>
> ---
>  tools/testing/selftests/kvm/Makefile          |  1 +
>  .../selftests/kvm/x86_64/hwcr_msr_test.c      | 52 +++++++++++++++++++
>  2 files changed, 53 insertions(+)
>  create mode 100644 tools/testing/selftests/kvm/x86_64/hwcr_msr_test.c
> 
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index a3bb36fb3cfc..6b0219ca65eb 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -135,6 +135,7 @@ TEST_GEN_PROGS_x86_64 += set_memory_region_test
>  TEST_GEN_PROGS_x86_64 += steal_time
>  TEST_GEN_PROGS_x86_64 += kvm_binary_stats_test
>  TEST_GEN_PROGS_x86_64 += system_counter_offset_test
> +TEST_GEN_PROGS_x86_64 += x86_64/hwcr_msr_test

Please place this with the other x86_64 specific tests.

Somewhat of a forward looking question, what do folks think about adding an
"msr_tests" subdirectory?  I really want to effectively replace KUT's msr.c test
with a supserset of functionality in selftests, e.g. KUT can't test userspace
writes.  But I don't want to end up with a single massive msr_test.c.  If we add
a subdirectory, then I think that would make it easier to share "private" APIs
and infrastructure without creating a giant monolithic test.

>  # Compiled outputs used by test targets
>  TEST_GEN_PROGS_EXTENDED_x86_64 += x86_64/nx_huge_pages_test
> diff --git a/tools/testing/selftests/kvm/x86_64/hwcr_msr_test.c b/tools/testing/selftests/kvm/x86_64/hwcr_msr_test.c
> new file mode 100644
> index 000000000000..1a6a09791ac3
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/x86_64/hwcr_msr_test.c
> @@ -0,0 +1,52 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2023, Google LLC.
> + *
> + * Tests for the K7_HWCR MSR.
> + */
> +
> +#define _GNU_SOURCE /* for program_invocation_short_name */
> +#include <sys/ioctl.h>
> +
> +#include "test_util.h"
> +#include "kvm_util.h"
> +#include "vmx.h"
> +
> +void test_hwcr_bit(struct kvm_vcpu *vcpu, unsigned int bit)
> +{
> +	const unsigned long long ignored = BIT_ULL(3) | BIT_ULL(6) | BIT_ULL(8);

uint64_t instead of "unsigned long long".

> +	const unsigned long long valid = BIT_ULL(18) | BIT_ULL(24);
> +	const unsigned long long legal = ignored | valid;
> +	uint64_t val = BIT_ULL(bit);
> +	uint64_t check;
> +	int r;
> +
> +	r = _vcpu_set_msr(vcpu, MSR_K7_HWCR, val);
> +	TEST_ASSERT((r == 1 && (val & legal)) || (r == 0 && !(val & legal)),
> +		    "Unexpected result (%d) when setting HWCR[bit %u]", r, bit);
> +	check =	vcpu_get_msr(vcpu, MSR_K7_HWCR);
> +	if (val & valid) {
> +		TEST_ASSERT(check == val,
> +			    "Bit %u: unexpected HWCR %lx; expected %lx", bit,
> +			    check, val);
> +		vcpu_set_msr(vcpu, MSR_K7_HWCR, 0);
> +	} else {
> +		TEST_ASSERT(!check,
> +			    "Bit %u: unexpected HWCR %lx; expected 0", bit,
> +			    check);
> +	}
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +	struct kvm_vm *vm;
> +	struct kvm_vcpu *vcpu;
> +	unsigned int bit;
> +
> +	vm = vm_create_with_one_vcpu(&vcpu, NULL);
> +
> +	for (bit = 0; bit < BITS_PER_LONG; bit++)
> +		test_hwcr_bit(vcpu, bit);
> +
> +	kvm_vm_free(vm);
> +}
> -- 
> 2.42.0.582.g8ccd20d70d-goog
>