linux-kernel - Re: [PATCH] pvh: set cr4 flags for APs

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Date:	Mon, 3 Feb 2014 11:30:01 -0800
From:	Mukesh Rathor <mukesh.rathor@...cle.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	boris.ostrovsky@...cle.com, david.vrabel@...rix.com,
	roger.pau@...rix.com, Xen-devel@...ts.xensource.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pvh: set cr4 flags for APs

On Mon, 3 Feb 2014 06:49:14 -0500
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com> wrote:

> On Wed, Jan 29, 2014 at 04:15:18PM -0800, Mukesh Rathor wrote:
> > We need to set cr4 flags for APs that are already set for BSP.
> 
> The title is missing the 'xen' part.

The patch is for linux, not xen.

> I rewrote it a bit and I think this should go in 3.14.
> 
> David, Boris: It is not the full fix as there are other parts to
> make an PVH guest use 2MB or 1GB pages- but this fixes an obvious
> bug.
> 
> 
> 
> From 797ea6812ff0a90cce966a4ff6bad57cbadc43b5 Mon Sep 17 00:00:00 2001
> From: Mukesh Rathor <mukesh.rathor@...cle.com>
> Date: Wed, 29 Jan 2014 16:15:18 -0800
> Subject: [PATCH] xen/pvh: set CR4 flags for APs
> 
> The Xen ABI sets said flags for the BSP, but it does

NO it does not. I said it few times, it's set by probe_page_size_mask
(which is in linux) for the BSP. The comment below also says it.

thanks
mukesh

> not do that for the CR4. As such fix it up to make
> sure we have that flag set.
> 
> Signed-off-by: Mukesh Rathor <mukesh.rathor@...cle.com>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> ---
>  arch/x86/xen/enlighten.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index a4d7b64..201d09a 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1473,6 +1473,18 @@ static void xen_pvh_set_cr_flags(int cpu)
>  	 * X86_CR0_TS, X86_CR0_PE, X86_CR0_ET are set by Xen for HVM
> guests
>  	 * (which PVH shared codepaths), while X86_CR0_PG is for
> PVH. */ write_cr0(read_cr0() | X86_CR0_MP | X86_CR0_NE | X86_CR0_WP |
> X86_CR0_AM); +
> +	if (!cpu)
> +		return;
> +	/*
> +	 * For BSP, PSE PGE are set in probe_page_size_mask(), for
> APs
> +	 * set them here. For all, OSFXSR OSXMMEXCPT are set in
> fpu_init.
> +	*/
> +	if (cpu_has_pse)
> +		set_in_cr4(X86_CR4_PSE);
> +
> +	if (cpu_has_pge)
> +		set_in_cr4(X86_CR4_PGE);
>  }
>  
>  /*

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