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From: Sunil Muthuswamy <sunilmut@microsoft.com>
To: Praveen Kumar <kumarpraveen@linux.microsoft.com>,
	"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: KY Srinivasan <kys@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	"wei.liu@kernel.org" <wei.liu@kernel.org>,
	Dexuan Cui <decui@microsoft.com>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"bp@alien8.de" <bp@alien8.de>, "x86@kernel.org" <x86@kernel.org>,
	"hpa@zytor.com" <hpa@zytor.com>,
	"viremana@linux.microsoft.com" <viremana@linux.microsoft.com>,
	"nunodasneves@linux.microsoft.com"
	<nunodasneves@linux.microsoft.com>
Subject: RE: [PATCH v4] hyperv: root partition faults writing to VP ASSIST MSR PAGE
Date: Sat, 31 Jul 2021 00:12:45 +0000	[thread overview]
Message-ID: <MW4PR21MB200206D615DEE60044B1F0A6C0ED9@MW4PR21MB2002.namprd21.prod.outlook.com> (raw)
In-Reply-To: <20210730171056.2820-1-kumarpraveen@linux.microsoft.com>

>  	hv_common_cpu_die(cpu);
> 
> -	if (hv_vp_assist_page && hv_vp_assist_page[cpu])
> -		wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, 0);
> +	if (hv_vp_assist_page && hv_vp_assist_page[cpu]) {
> +		union hv_vp_assist_msr_contents msr = {0};
> +		if (hv_root_partition) {
> +			/*
> +			 * For Root partition the VP ASSIST page is mapped to
> +			 * hypervisor provided page, and thus, we unmap the
> +			 * page here and nullify it, so that in future we have
> +			 * correct page address mapped in hv_cpu_init.
> +			 */
> +			memunmap(hv_vp_assist_page[cpu]);
> +			hv_vp_assist_page[cpu] = NULL;
> +			rdmsrl(HV_X64_MSR_VP_ASSIST_PAGE, msr.as_uint64);

If the vp assist page was previously enabled for root, it will continue to stay enabled
when you 'wrmsr' below. We need to explicitly set the enable bit to 0.

> +		}
> +		wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, msr.as_uint64);
> +	}

      reply	other threads:[~2021-07-31  0:12 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-30 17:10 [PATCH v4] hyperv: root partition faults writing to VP ASSIST MSR PAGE Praveen Kumar
2021-07-31  0:12 ` Sunil Muthuswamy [this message]

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