From mboxrd@z Thu Jan 1 00:00:00 1970 From: George Dunlap Subject: Re: Xen 4.3 development update RC2 imminent Date: Thu, 23 May 2013 15:35:08 +0100 Message-ID: <519E291C.7050206@eu.citrix.com> References: <519B7F67.2050602@citrix.com> <519B8541.8090505@citrix.com> <519BA6F302000078000D7CF2@nat28.tlf.novell.com> <519B9D15.7060004@eu.citrix.com> <519B9DF9.7090303@eu.citrix.com> <519CBEF3.4020701@m2r.biz> <519CDEB7.5090608@eu.citrix.com> <20130522163028.GU11427@reaktio.net> <519CF85D.5070702@eu.citrix.com> <519DE3D702000078000D85B4@nat28.tlf.novell.com> <519DF133.1020808@m2r.biz> <519DF1C4.6050809@citrix.com> <519DF568.1010906@eu.citrix.com> <519E24DD.4080901@m2r.biz> <519E270C.5040206@eu.citrix.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============6176658924503522984==" Return-path: In-Reply-To: <519E270C.5040206@eu.citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Fabio Fantoni Cc: Anthony Perard , Andrew Cooper , Jan Beulich , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org --===============6176658924503522984== Content-Type: multipart/alternative; boundary="------------080003060806070200010903" --------------080003060806070200010903 Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit On 23/05/13 15:26, George Dunlap wrote: > On 23/05/13 15:17, Fabio Fantoni wrote: >> Il 23/05/2013 12:54, George Dunlap ha scritto: >>> On 23/05/13 11:39, Andrew Cooper wrote: >>>> On 23/05/13 11:36, Fabio Fantoni wrote: >>>>> Il 23/05/2013 09:39, Jan Beulich ha scritto: >>>>>>>>> On 22.05.13 at 18:54, George Dunlap >>>>>>>>> wrote: >>>>>>> On 22/05/13 17:30, Pasi Kärkkäinen wrote: >>>>>>>> On Wed, May 22, 2013 at 04:05:27PM +0100, George Dunlap wrote: >>>>>>>> Hmm, for testing, can we use cpuid to mask out SSE, >>>>>>>> and then try qxl ? >>>>>>> That had occurred to me -- Andrew / Jan, do you know which flag >>>>>>> might >>>>>>> disable this particular instruction? >>>>>>> >>>>>>> I guess we could try just disabling all the SSE instructions. >>>>>> movdqu is an SSE2 instruction, so disabling bit 26 of CPUID EDX >>>>>> output to EAX=1 input. >>>>> Can you explain better please? >>>>> Should I add this to test it? >>>>> cpuid="host,sse=0,sse2=0,ssse3=0,sse4_1=0,sse4_2=0,eax=1" >>>> It will likely not work. SSE2 is an architectural requirement for >>>> 64bit. >>>> >>>> It means that 64bit code may assume the presence of SSE2. Xen amongst >>>> other software does make this assumption. >>> >>> It might work if he's using 32-bit. >>> >>> Fabio, as I said in my initial e-mail, you need to: >>> >>> 1. Run "cat /proc/cpuinfo" on your dom0 >>> 2. Look at the line that says "features:" >>> 3. Find all the things that contain "sse" > 2 (sse2, ssse3, &c) >>> 4. Set them to 0 in the "cpuid" field like above. >>> >>> Every processor will be a bit different -- you can't just copy mine >>> and expect it to work. >>> >>> Don't include "eax=1" -- Jan is thinking of a different interface. >>> >>> -George >> Tried with Raring (ubuntu 13.04) 32bit... >> in cfg: >> cpuid="host,sse=0,sse2=0,ssse3=0,sse4_1=0,sse4_2=0" >> >> # xl create /etc/xen/RARING.cfg >> Parsing config from /etc/xen/RARING.cfg >> while parsing CPUID flag: "sse4_1=0": >> error #2: unknown CPUID flag name >> while parsing CPUID flag: "sse4_2=0": >> error #2: unknown CPUID flag name > > Right -- in that case this is a minor bug in libxl. (Actually I got > the same result, I just didn't notice the error messages -- sorry > about that.) Actually it's not a bug per se; libxl apparently just calls these sse4.1 and sse4.2 respectively. -George --------------080003060806070200010903 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: 8bit
On 23/05/13 15:26, George Dunlap wrote:
On 23/05/13 15:17, Fabio Fantoni wrote:
Il 23/05/2013 12:54, George Dunlap ha scritto:
On 23/05/13 11:39, Andrew Cooper wrote:
On 23/05/13 11:36, Fabio Fantoni wrote:
Il 23/05/2013 09:39, Jan Beulich ha scritto:
On 22.05.13 at 18:54, George Dunlap <george.dunlap@eu.citrix.com> wrote:
On 22/05/13 17:30, Pasi Kärkkäinen wrote:
On Wed, May 22, 2013 at 04:05:27PM +0100, George Dunlap wrote:
Hmm, for testing, can we use cpuid to mask out SSE,
and then try qxl ?
That had occurred to me -- Andrew / Jan, do you know which flag might
disable this particular instruction?

I guess we could try just disabling all the SSE instructions.
movdqu is an SSE2 instruction, so disabling bit 26 of CPUID EDX
output to EAX=1 input.
Can you explain better please?
Should I add this to test it?
cpuid="host,sse=0,sse2=0,ssse3=0,sse4_1=0,sse4_2=0,eax=1"
It will likely not work.  SSE2 is an architectural requirement for 64bit.

It means that 64bit code may assume the presence of SSE2.  Xen amongst
other software does make this assumption.

It might work if he's using 32-bit.

Fabio, as I said in my initial e-mail, you need to:

1. Run "cat /proc/cpuinfo" on your dom0
2. Look at the line that says "features:"
3. Find all the things that contain "sse" > 2 (sse2, ssse3, &c)
4. Set them to 0 in the "cpuid" field like above.

Every processor will be a bit different -- you can't just copy mine and expect it to work.

Don't include "eax=1" -- Jan is thinking of a different interface.

 -George
Tried with Raring (ubuntu 13.04) 32bit...
in cfg:
cpuid="host,sse=0,sse2=0,ssse3=0,sse4_1=0,sse4_2=0"

# xl create /etc/xen/RARING.cfg
Parsing config from /etc/xen/RARING.cfg
while parsing CPUID flag: "sse4_1=0":
  error #2: unknown CPUID flag name
while parsing CPUID flag: "sse4_2=0":
  error #2: unknown CPUID flag name

Right -- in that case this is a minor bug in libxl.  (Actually I got the same result, I just didn't notice the error messages -- sorry about that.)

Actually it's not a bug per se; libxl apparently just calls these sse4.1 and sse4.2 respectively.

 -George

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