linux-kernel - Re: [PATCH v14 11/11] selftests: kvm/x86: add test for pmu msr MSR_IA32_PERF

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Date:   Tue, 2 Feb 2021 15:53:38 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Like Xu <like.xu@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, ak@...ux.intel.com,
        wei.w.wang@...el.com, kan.liang@...el.com,
        alex.shi@...ux.alibaba.com, kvm@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v14 11/11] selftests: kvm/x86: add test for pmu msr
 MSR_IA32_PERF_CAPABILITIES

On 01/02/21 07:01, Like Xu wrote:
> 
> +uint64_t rdmsr_on_cpu(uint32_t reg)
> +{
> +	uint64_t data;
> +	int fd;
> +	char msr_file[64];
> +
> +	sprintf(msr_file, "/dev/cpu/%d/msr", 0);
> +	fd = open(msr_file, O_RDONLY);
> +	if (fd < 0)
> +		exit(KSFT_SKIP);
> +
> +	if (pread(fd, &data, sizeof(data), reg) != sizeof(data))
> +		exit(KSFT_SKIP);
> +
> +	close(fd);
> +	return data;
> +}

In order to allow running as non-root, it's better to use the 
KVM_GET_MSRS ioctl on the /dev/kvm file descriptor.

The tests pass, but please take a look at the kvm/queue branch to see if 
everything is ok.

Paolo