linux-kernel - Re: [Xen-devel] [V0 PATCH 1/2] AMD-PVH: set EFER.NX and EFER.SCE for the boot vcpu

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Fri, 22 Aug 2014 16:29:07 -0700
From:	Mukesh Rathor <mukesh.rathor@...cle.com>
To:	Mukesh Rathor <mukesh.rathor@...cle.com>
Cc:	Borislav Petkov <bp@...en8.de>, xen-devel@...ts.xenproject.org,
	boris.ostrovsky@...cle.com, david.vrabel@...rix.com,
	linux-kernel@...r.kernel.org
Subject: Re: [Xen-devel] [V0 PATCH 1/2] AMD-PVH: set EFER.NX and EFER.SCE
 for the boot vcpu

On Fri, 22 Aug 2014 12:09:27 -0700
Mukesh Rathor <mukesh.rathor@...cle.com> wrote:

> On Fri, 22 Aug 2014 06:41:40 +0200
> Borislav Petkov <bp@...en8.de> wrote:
> 
> > On Thu, Aug 21, 2014 at 07:46:56PM -0700, Mukesh Rathor wrote:
> > > Intel doesn't have EFER.NX bit.
> > 
> > Of course it does.
> > 
> 
> Right, it does. Some code/comment is misleading... Anyways, reading
> intel SDMs, if I understand the convoluted text correctly, EFER.NX is
> not required to be set for l1.nx to be set, thus allowing for page
> level protection. Where as on AMD, EFER.NX must be set for l1.nx to
> be used. So, in the end, this patch would apply to both amd/intel.... 
> 
> I'll reword and submit.

Err, try again, the section "4.1.1 Three Paging Modes" says:

"Execute-disable access rights are applied only if IA32_EFER.NXE = 1"

So, I guess NX is broken on Intel PVH because EFER.NX is currently 
not being set.  While AMD will #GP if l1.NX is set and EFER.NX is not, 
I guess Intel just ignores the l1.XD if EFER.NX is not set. 

Mukesh
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/