From: Keir Fraser <keir.xen@gmail.com>
To: Stefan Bader <stefan.bader@canonical.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: wei.y.yang@intel.com,
"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
haitao.shan@intel.com, xin.li@intel.com,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: Xen HVM regression on certain Intel CPUs
Date: Wed, 27 Mar 2013 20:24:58 +0000 [thread overview]
Message-ID: <CD79061A.1F6E4%keir.xen@gmail.com> (raw)
In-Reply-To: <5153222B.3030605@canonical.com>
On 27/03/2013 16:45, "Stefan Bader" <stefan.bader@canonical.com> wrote:
>>> Seems that I was relying on the wrong source of information when checking
>>> SMEP
>>> support. The cpuid command seems at fail. But /proc/cpuinfo reports it. So
>>> that
>>> at least explains where that comes from... sorry for that.
>>
>> OK, so if you boot Xen with smep=1 (which disables SMEP, kind of
>> counterintuive flag)
>> that would work fine?
>
> Rebooting with smep=1 as a hv argument does not fix it. But I would be careful
> since I just quickly did this without checking whether Xen 4.2.1 undestands
> the
> flag already.
Yes, the flag is understood by all Xen 4.2 releases. However it is not
inverted as you believe: it really is smep=0 or smep=off or even no-smep to
disable SMEP. smep=1 will enable SMEP (which is the default anyway).
I also checked how CPUID.SMEP gets set for an HVM guest, and it is very
obviously masked off if SMEP support has been disabled or is unavailable. So
I do not think we can be erroneously passing the CPUID flag to the guest.
-- Keir
next prev parent reply other threads:[~2013-03-27 20:24 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-27 15:26 Xen HVM regression on certain Intel CPUs Stefan Bader
2013-03-27 15:53 ` Stefan Bader
2013-03-27 16:04 ` Konrad Rzeszutek Wilk
2013-03-27 16:09 ` H. Peter Anvin
2013-03-27 16:24 ` Stefan Bader
2013-03-27 16:32 ` H. Peter Anvin
2013-03-27 16:32 ` Stefano Stabellini
2013-03-27 16:45 ` Stefan Bader
2013-03-27 16:52 ` H. Peter Anvin
2013-03-27 17:17 ` Stefan Bader
2013-03-27 17:23 ` H. Peter Anvin
2013-03-27 17:38 ` Stefan Bader
2013-03-28 13:34 ` Jan Beulich
2013-03-28 15:02 ` Stefan Bader
2013-03-28 16:39 ` Stefan Bader
2013-04-03 11:56 ` Stefan Bader
2013-04-03 12:43 ` Jan Beulich
2013-04-03 14:28 ` Keir Fraser
2013-04-03 15:00 ` Xu, Dongxiao
2013-04-03 15:48 ` H. Peter Anvin
2013-04-03 16:05 ` Jan Beulich
2013-03-27 17:28 ` Stefan Bader
2013-03-27 17:30 ` H. Peter Anvin
2013-03-27 17:40 ` Stefan Bader
2013-03-27 17:44 ` H. Peter Anvin
2013-03-27 20:24 ` Keir Fraser [this message]
2013-03-28 15:06 ` Stefan Bader
2013-03-28 15:42 ` H. Peter Anvin
2013-03-28 16:12 ` Stefan Bader
2013-03-27 16:18 ` H. Peter Anvin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CD79061A.1F6E4%keir.xen@gmail.com \
--to=keir.xen@gmail.com \
--cc=haitao.shan@intel.com \
--cc=hpa@zytor.com \
--cc=konrad.wilk@oracle.com \
--cc=stefan.bader@canonical.com \
--cc=wei.y.yang@intel.com \
--cc=xen-devel@lists.xensource.com \
--cc=xin.li@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.