linux-kernel - Re: [PATCH] kvm: x86: emulate MSR_PLATFORM

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Message-ID: <ZOMWM+YmScUG3U5W@chao-email>
Date:   Mon, 21 Aug 2023 15:52:01 +0800
From:   Chao Gao <chao.gao@...el.com>
To:     Hao Xiang <hao.xiang@...ux.alibaba.com>
CC:     <kvm@...r.kernel.org>, <shannon.zhao@...ux.alibaba.com>,
        <pbonzini@...hat.com>, <seanjc@...gle.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kvm: x86: emulate MSR_PLATFORM_INFO msr bits

On Mon, Aug 21, 2023 at 11:26:32AM +0800, Hao Xiang wrote:
>For intel platform, The BzyMhz field of Turbostat shows zero
>due to the missing of part msr bits of MSR_PLATFORM_INFO.
>
>Acquire necessary msr bits, and expose following msr info to guest,
>to make sure guest can get correct turbo frequency info.

Userspace VMM (e.g., QEMU) can configure this MSR for guests. Please refer to
tools/testing/selftests/kvm/x86_64/platform_info_test.c.

The question is why KVM needs this patch given KVM already provides interfaces
for QEMU to configure the MSR.