linux-kernel - Re: [PATCH] xen/x86: Don't try to write syscall-related MSRs for PV guests

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Date:	Mon, 21 Sep 2015 11:30:35 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc:	david.vrabel@...rix.com, xen-devel@...ts.xenproject.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xen/x86: Don't try to write syscall-related MSRs for PV
 guests

On Mon, Sep 21, 2015 at 09:09:28AM -0400, Boris Ostrovsky wrote:
> For PV guests these registers are set up by hypervisor and thus
> should not be written by the guest. The comment in xen_write_msr_safe()
> says so but we still write the MSRs, causing the hypervisor to
> print a warning.
> 
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>

> ---
>  arch/x86/xen/enlighten.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 30d12af..1f1dbd2 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1077,6 +1077,7 @@ static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
>  		/* Fast syscall setup is all done in hypercalls, so
>  		   these are all ignored.  Stub them out here to stop
>  		   Xen console noise. */
> +		break;
>  
>  	default:
>  		if (!pmu_msr_write(msr, low, high, &ret))
> -- 
> 2.1.0
> 
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