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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).