linux-kernel - Re: [PATCH v3] hyperv: root partition faults writing to VP ASSIST MSR PAGE

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Message-ID: <20210727175131.364fxm667marijdk@liuwe-devbox-debian-v2>
Date:   Tue, 27 Jul 2021 17:51:31 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Praveen Kumar <kumarpraveen@...ux.microsoft.com>
Cc:     linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        wei.liu@...nel.org, decui@...rosoft.com, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
        viremana@...ux.microsoft.com, sunilmut@...rosoft.com,
        nunodasneves@...ux.microsoft.com
Subject: Re: [PATCH v3] hyperv: root partition faults writing to VP ASSIST
 MSR PAGE

On Tue, Jul 27, 2021 at 04:10:44PM +0530, Praveen Kumar wrote:
[...]
>  
> @@ -170,9 +185,21 @@ static int hv_cpu_die(unsigned int cpu)
>  
>  	hv_common_cpu_die(cpu);
>  
> -	if (hv_vp_assist_page && hv_vp_assist_page[cpu])
> +	if (hv_vp_assist_page && hv_vp_assist_page[cpu]) {
>  		wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, 0);
>  

The content of the MSR should be preserved; otherwise you hit the same
fault for root kernel.

Wei.