From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Jan Beulich" <JBeulich@suse.com>
Subject: Re: [PATCH 1/2] x86/xen: Set EFER.NX and EFER.SCE in
 PVH guests
Date: Fri, 05 Sep 2014 15:34:40 +0100
Message-ID: <5409E6200200007800031869@mail.emea.novell.com>
References: <1409926309-8345-1-git-send-email-david.vrabel@citrix.com>
	<1409926309-8345-2-git-send-email-david.vrabel@citrix.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
Received: from mail6.bemta4.messagelabs.com ([85.158.143.247])
	by lists.xen.org with esmtp (Exim 4.72)
	(envelope-from <JBeulich@suse.com>) id 1XPub3-0003cu-OJ
	for xen-devel@lists.xenproject.org; Fri, 05 Sep 2014 14:34:41 +0000
In-Reply-To: <1409926309-8345-2-git-send-email-david.vrabel@citrix.com>
Content-Disposition: inline
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: David Vrabel <david.vrabel@citrix.com>
Cc: xen-devel@lists.xenproject.org, Boris Ostrovsky <boris.ostrovsky@oracle.com>
List-Id: xen-devel@lists.xenproject.org

>>> On 05.09.14 at 16:11, <david.vrabel@citrix.com> wrote:
> --- a/arch/x86/xen/xen-head.S
> +++ b/arch/x86/xen/xen-head.S
> @@ -47,6 +47,36 @@ ENTRY(startup_xen)
>  
>  	__FINIT
>  
> +#ifdef CONFIG_XEN_PVH
> +
> +/**
> + * xen_pvh_cpu_early_init() - early PVH VCPU initialization
> + * @cpu: this cpu number (%rdi)
> + *
> + * Note: This is called as a function on the boot CPU and as the secondary
> + * CPU entry point.
> + */
> +ENTRY(xen_pvh_cpu_early_init)
> +	/* Gather features to see if NX implemented. */
> +	mov     $0x80000001, %eax
> +	cpuid
> +	mov     %edx,%esi
> +
> +	mov     $MSR_EFER, %ecx
> +	rdmsr
> +	bts     $_EFER_SCE, %eax
> +
> +	bt      $20,%esi
> +	jnc     1f      /* No NX, skip setting it */
> +	bts     $_EFER_NX, %eax
> +1:	wrmsr
> +
> +	cmp     $0,%rdi /* non-zero => secondary cpu */

Isn't Linux is specifically moving away from this assumption?

> +	jne     cpu_bringup_and_idle
> +	ret
> +
> +#endif /* CONFIG_XEN_PVH */

Also, does all this really need to be done in assembly?

Jan