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Message-ID: <6d10dcf7-7912-25a2-8d8e-ef7d71a4ce83@linux.alibaba.com>
Date: Mon, 21 Aug 2023 17:11:16 +0800
From: Hao Xiang <hao.xiang@...ux.alibaba.com>
To: Chao Gao <chao.gao@...el.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
For reason that,
The turbo frequency info depends on specific machine type. And the msr
value of MSR_PLATFORM_INFO may be diferent on diffrent generation machine.
Get following msr bits (needed by turbostat on intel platform) by rdmsr
MSR_PLATFORM_INFO directly in KVM is more reasonable. And set these msr
bits as vcpu->arch.msr_platform_info default value.
-bit 15:8, Maximum Non-Turbo Ratio (MAX_NON_TURBO_LIM_RATIO)
-bit 47:40, Maximum Efficiency Ratio (MAX_EFFICIENCY_RATIO)
On 2023/8/21 15:52, Chao Gao wrote:
> 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.
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