Xen devel - May 2006 - [PATCH][HVMLOADER][DISCUSS] 8 way default rombios

Attached simple patch modifies the rombios and hvmloader Makefiles to
default to an 8-way bochs bios for the hvmloader.

Is there a reason to not define the mp config table by default for >1
processors (8), in the repository?

Seems like using the hvm guest config file can the methodolody to
describe a UP guest regardless of the mptables. 
Defaulting the rombios to MP would allow users to experiment with SMP
guests, while allowing UP guests to work.

Thanks
Tom  


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ACPI MADT is sufficient for getting >1 vcpus (just add vcpus=N at xm
create time) for modern OSes, but the mp config table would be required
for old guests. So I think the patch is sensible.

Jun
---
Intel Open Source Technology Center 

-----Original Message-----
From: xen-devel-bounces@lists.xensource.com
[mailto:xen-devel-bounces@lists.xensource.com] On Behalf Of Woller,
Thomas
Sent: Tuesday, May 30, 2006 3:01 PM
To: xen-devel@lists.xensource.com
Subject: [Xen-devel] [PATCH][HVMLOADER][DISCUSS] 8 way default rombios

Attached simple patch modifies the rombios and hvmloader Makefiles to
default to an 8-way bochs bios for the hvmloader.

Is there a reason to not define the mp config table by default for >1
processors (8), in the repository?

Seems like using the hvm guest config file can the methodolody to
describe a UP guest regardless of the mptables. 
Defaulting the rombios to MP would allow users to experiment with SMP
guests, while allowing UP guests to work.

Thanks
Tom  

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Tom,

On latest xen-unstable, when installing Windows XP, it''ll loop forever
at Windows setup.  Then we found this is  caused by your
''xen-8-way-bios.patch'' in changset 10191, your patch added an
8 vcpu MPS
table (pnp mode) to the HVM BIOS,  This is probably fine for Linux SMP
Guest but is screwing up Windows because Windows do not understand what
kind of platform it is and then install the wrong HAL for it.

Here is my suggestion for you:
If you want to add SMP support for MPS table, you need to check HVM
guest configuration file for the switches for acpi and vcpu =number:

   if (vcpu !=1 &acpi=0)
     build xen-(vcpu number)-way-bios
     ...
Just as Jun pointed out  MPS table is used for old guest OS (plug and
play mode +APM) mode, not for ACPI,


Here is a method how to  install guest Windows XP (using you patch) by
telling Windows what kind of platform at Windows setup (this is true for
Win2k, 2003 and XP):

After passing the 1st screen of windows setup of install XP, the first
thing you''ll see at the bottom of the screen is the option to press F6
if you need to install a SCSI or RAID controller. Don''t press F6. Press
F5 instead. This will take you to a separate menu of Hardware
Abstraction Layer''s where you can choose an appropriate HAL .The
choices
are:

ACPI Multiprocessor PC 
ACPI Uniprocessor PC 
Advanced Configuration and Power Interface (ACPI) PC 
Compaq SystemPro Multiprocessor or 100% Compatible PC 
MPS Uniprocessor PC 
MPS Multiprocessor PC 
Standard PC 
Standard PC with C-Step i486 
Other

Select "Standard PC". This will allow the installation to complete in
about 20 minutes. 

If we revert your patch, we don''t need the above press F5 to get guest
Windows installed.

Regards,

Winston,
>>> -----Original Message-----
>>> From: xen-devel-bounces@lists.xensource.com
>>> [mailto:xen-devel-bounces@lists.xensource.com] On Behalf Of
>>> Nakajima, Jun Sent: Tuesday, May 30, 2006 4:01 PM
>>> To: Woller, Thomas; xen-devel@lists.xensource.com
>>> Subject: RE: [Xen-devel] [PATCH][HVMLOADER][DISCUSS] 8 way default
>>> rombios 
>>> 
>>> ACPI MADT is sufficient for getting >1 vcpus (just add vcpus=N
at xm
>>> create time) for modern OSes, but the mp config table would be
>>> required for old guests. So I think the patch is sensible.
>>> 
>>> Jun
>>> ---
>>> Intel Open Source Technology Center
>>> 
>>> -----Original Message-----
>>> From: xen-devel-bounces@lists.xensource.com
>>> [mailto:xen-devel-bounces@lists.xensource.com] On Behalf Of Woller,
>>> Thomas Sent: Tuesday, May 30, 2006 3:01 PM
>>> To: xen-devel@lists.xensource.com
>>> Subject: [Xen-devel] [PATCH][HVMLOADER][DISCUSS] 8 way default
>>> rombios 
>>> 
>>> Attached simple patch modifies the rombios and hvmloader Makefiles
>>> to default to an 8-way bochs bios for the hvmloader.
>>> 
>>> Is there a reason to not define the mp config table by default for
>>> >1 processors (8), in the repository?
>>> 
>>> Seems like using the hvm guest config file can the methodolody to
>>> describe a UP guest regardless of the mptables.
>>> Defaulting the rombios to MP would allow users to experiment with
>>> SMP guests, while allowing UP guests to work.
>>> 
>>> Thanks
>>> Tom
>>> 
>>> _______________________________________________
>>> Xen-devel mailing list
>>> Xen-devel@lists.xensource.com
>>> http://lists.xensource.com/xen-devel
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On 7 Jun 2006, at 05:55, Wang, Winston L wrote:
> Here is my suggestion for you:
> If you want to add SMP support for MPS table, you need to check HVM
> guest configuration file for the switches for acpi and vcpu =number:
>
>    if (vcpu !=1 &acpi=0)
>      build xen-(vcpu number)-way-bios
>      ...
> Just as Jun pointed out  MPS table is used for old guest OS (plug and
> play mode +APM) mode, not for ACPI,
The best way would be to do the same as the for our ACPI tables -- 
dynamically generate the CPU entries (LAPIC entries in case of ACPI 
tables) when we know how many VCPUs the guest has been allocated.

This would get rid of multiple statically-compiled rombios images, each 
of which only differs in CPU info in the MPS table. It could even be 
hacked up without modifying rombios image -- e.g., hvmloader could scan 
for and then modify the MPS table to insert secondary-processor 
entries. It wouldn''t be very hard to do.

In any case, I''ll revert the earlier patch. Using a MPS table that 
advertises 8 processors when a guest actually has fewer doesn''t seem a 
very wise idea.

  -- Keir


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Thank you winston! 
we were performing the same experiments yesterday after our regression
*finally* found the same problem... a bit late though, after the patch
was applied to both trees.  
> The best way would be to do the same as the for our ACPI 
> tables -- dynamically generate the CPU entries (LAPIC entries 
> in case of ACPI
> tables) when we know how many VCPUs the guest has been allocated.
> 
> This would get rid of multiple statically-compiled rombios 
> images, each of which only differs in CPU info in the MPS 
> table. It could even be hacked up without modifying rombios 
> image -- e.g., hvmloader could scan for and then modify the 
> MPS table to insert secondary-processor entries. It wouldn''t 
> be very hard to do.
> 
> In any case, I''ll revert the earlier patch. Using a MPS table 
> that advertises 8 processors when a guest actually has fewer 
> doesn''t seem a very wise idea.
Agreed. Reversion is probably best here for both unstable and
3.0-testing. I''ll take a gander at adding the tables dynamically in
hvmloader, and see if I can get a preliminary patch out in a couple of
days - need to test quite a few configurations.
Thanks
Tom


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On 7 Jun 2006, at 13:30, Woller, Thomas wrote:
> Thank you winston!
> we were performing the same experiments yesterday after our regression
> *finally* found the same problem... a bit late though, after the patch
> was applied to both trees.
The patch was applied only to -unstable. It''s been reverted there.

  -- Keir


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Thanks for taking care of this.
Winston,
Keir Fraser wrote:
> On 7 Jun 2006, at 13:30, Woller, Thomas wrote:
> 
>> Thank you winston!
>> we were performing the same experiments yesterday after our
>> regression *finally* found the same problem... a bit late though,
>> after the patch was applied to both trees.
> 
> The patch was applied only to -unstable. It''s been reverted there.
> 
>   -- Keir
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