linux-kernel - Re: [PATCH] KVM: selftests: x86: Skip unsupported test when Arch LBR is available

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Date:   Tue, 10 May 2022 11:06:38 -0400
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Yang Weijiang <weijiang.yang@...el.com>
Cc:     pbonzini@...hat.com, likexu@...cent.com,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH] KVM: selftests: x86: Skip unsupported test when Arch LBR is available

Hi,

> -	ret = _vcpu_set_msr(vm, 0, MSR_IA32_PERF_CAPABILITIES, PMU_CAP_LBR_FMT);
> -	TEST_ASSERT(ret == 0, "Bad PERF_CAPABILITIES didn't fail.");
> +	/* Note, on Arch LBR capable platforms, LBR_FMT in perf capability msr is 0x3f,
> +	 * so skip below test if running on these platforms. */
> +	if (host_cap.lbr_format != PMU_CAP_LBR_FMT) {
> +		ret = _vcpu_set_msr(vm, 0, MSR_IA32_PERF_CAPABILITIES, PMU_CAP_LBR_FMT);
> +		TEST_ASSERT(ret == 0, "Bad PERF_CAPABILITIES didn't fail.");
> +	}

Why not try a different value?

Paolo