linux-kernel - Re: [Xen-devel] [V5 PATCH 1/1] x86/xen: Set EFER.NX and EFER.SCE in PVH guests

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Message-ID: <5425A1CE.7090704@citrix.com>
Date:	Fri, 26 Sep 2014 18:26:38 +0100
From:	David Vrabel <david.vrabel@...rix.com>
To:	Mukesh Rathor <mukesh.rathor@...cle.com>,
	<boris.ostrovsky@...cle.com>, <david.vrabel@...rix.com>
CC:	<xen-devel@...ts.xenproject.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [V5 PATCH 1/1] x86/xen: Set EFER.NX and EFER.SCE
 in PVH guests

On 11/09/14 00:36, Mukesh Rathor wrote:
> This fixes two bugs in PVH guests:
> 
>   - Not setting EFER.NX means the NX bit in page table entries is
>     ignored on Intel processors and causes reserved bit page faults on
>     AMD processors.
> 
>   - After the Xen commit 7645640d6ff1 ("x86/PVH: don't set EFER_SCE for
>     pvh guest") PVH guests are required to set EFER.SCE to enable the
>     SYSCALL instruction.
> 
> Secondary VCPUs are started with pagetables with the NX bit set so
> EFER.NX must be set before using any stack or data segment.
> xen_pvh_cpu_early_init() is the new secondary VCPU entry point that
> sets EFER before jumping to cpu_bringup_and_idle().

Applied to devel/for-linus-3.18

Thanks.

David
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