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Re: [Xen-devel] [PATCH][HVMLOADER][DISCUSS] 8 way default rombios

To: "Wang, Winston L" <winston.l.wang@xxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH][HVMLOADER][DISCUSS] 8 way default rombios
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Wed, 7 Jun 2006 09:54:15 +0100
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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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