RE: [Xen-devel] Fix for 'acpi=off'

["Puthiyaparambil, Aravindh" <aravindh.puthiyaparambil@xxxxxxxxxx>]

I am a little confused here. 

I have configured Dom0 to be a uniprocessor kernel. Shouldn't that stop
SMP specific code from being executed?

Won't setting num_processors=1 cause Dom0 to always be uniproc even if
SMP is turned on? 

Aravindh

-----Original Message-----
From: Arun Sharma [mailto:arun.sharma@xxxxxxxxx] 
Sent: Thursday, May 05, 2005 7:10 PM
To: Puthiyaparambil, Aravindh
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] Fix for 'acpi=off'

Puthiyaparambil, Aravindh wrote:
> I tried the acpi=off on my 2-by x86_64 box running 32-bit SLES9.
> Everything seems to work just fine except for a couple of pfn and page
> fault non-fatal errors.
> 
> But with acpi=ht, Dom0 hangs while trying to bring up the SCSI
devices.
> I have included debug output for both cases.
> 

I think this is the issue you're running into:

> SMP mptable: no processors registered!
> BIOS bug, MP table errors detected!...
> ... disabling SMP support. (tell your hw vendor)

With acpi=off acpi_lapic is non-zero so this code works:

    /* ACPI may have already provided this data */
    if (!acpi_lapic)
            MP_processor_info(m);

But with acpi=ht, MP table processor info is ignored. I worked around it
by ignoring the processor entries in the MP table always and setting
num_processors=1.

        -Arun


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