Re: [Xen-devel] Only one CPU core detected when booting on UEFI

[Jacek Konieczny <jajcus@xxxxxxxxxx>]

Hi,

On Fri, Dec 21, 2012 at 09:30:59PM -0500, Xiao-Long Chen wrote:
> > Hm, this:
> > [    0.000000] ACPI BIOS Bug: Error: A valid RSDP was not found
> > (20120913/tbxfroot-219)
> >
> > is a problem. The workaround was mentioned on the mailing list to use
> > the acpi_rsdp=0xbabfe000

> I tried booting with this, but the kernel immediately crashed
> (I think). I booted with 'acpi_rsdp=0xbabfe000' and without 'quiet' and
> the system hangs while loading the initramfs. I could not see any sort
> of response on the system and could not ssh in.

I posted the workaround, and it was not 'acpi_rsdp=0xbabfe000',
but 'acpi_rsdp=the-value-xen-reports' (it could be 0xbabfe000 for a
specific machine)

> > Did you try to boot xen.efi by itself - without using the GRUB loader?
> > There is a nice writeup of how to do this in docs/misc/efi.markdown.

GRUB2 still may be used, but only for chain-loading the xen.efi. This
give little gain over booting xen.efi directly from the firmware,
though.

> Booting from xen.efi, I see "Dom0 has maximum 8 VCPUs" as expected,

Now xen can find the ACPI RSDP

> but Linux is still seeing only one core.

That is because Xen doesn't pass all the information obtained via EFI to
the kernel.

> xl dmesg: http://paste.kde.org/629696/raw/

the important part:

> (XEN) ACPI: RSDP BABFE014, 0024 (r2 LENOVO)

Try booting xen.efi and passing 'acpi_rsdp=0xBABFE014' to the kernel via
the kernel command-line.

This should fix other problems with the kernel too, as ACPI is important
for initializing many kernel subsystems.

Greets,
        Jacek

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