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Re: [Qemu-devel] AMD 100% CPU bug; patch available?
From: |
David Barrett |
Subject: |
Re: [Qemu-devel] AMD 100% CPU bug; patch available? |
Date: |
Tue, 12 Aug 2008 13:31:47 -0700 |
User-agent: |
Thunderbird 2.0.0.16 (X11/20080724) |
Aha, figured it out. The tip was in dmesg on the guest:
DMI not present or invalid.
ACPI: RSDP signature @ 0xC00FB010 checksum 0
ACPI: RSDP 000FB010, 0014 (r0 QEMU )
ACPI: RSDT 07FF0000, 002C (r1 QEMU QEMURSDT 1 QEMU
1)
ACPI: FACP 07FF002C, 0074 (r1 QEMU QEMUFACP 1 QEMU
1)
ACPI: DSDT 07FF0100, 0832 (r1 BXPC BXDSDT 1 INTL 20061
109)
ACPI: FACS 07FF00C0, 0040
ACPI: APIC 07FF0938, 0040 (r1 QEMU QEMUAPIC 1 QEMU
ACPI: no DMI BIOS year, acpi=force is required to enable ACPI
ACPI: Disabling ACPI support
Adding acpi=force to the kernel boot line fixed it up.
(Though strangely, even after adding acpi=force to the kernel boot line,
it still dumps this exact same message -- odd. At least the problem
went away.)
Thanks for the help!
-david
Rick Vernam wrote:
I'm not so sure there is such a bug - I've been running qemu on AMD 3700
laptop for years w/o that, or much of any other issue (except once upon a
time an ACPI issue w/ windows guest causing host cpu to peg 100%).
I run gentoo host + various windows/linux guests.
points of interest may (or may not) be details such as host kernel
configuration? qemu version? qemu options used? built yourself or
pre-packaged?
I don't claim to be able to help you solve the problem, but there's not much
here to work with...
On Tuesday 12 August 2008 11:36:08 am David Barrett wrote:
Can anybody confirm that qemu works on an AMD processor with a Linux
host and Linux guest (ideally Ubuntu 8.04 in both cases) without using
100% CPU? (qemu process on the host uses 100% CPU despite all processes
on the guest being idle.)
Or is there a known bug that qemu with a Ubuntu guest always uses 100%
CPU on AMD Ubuntu hosts? If so, is there a patch or workaround for it?
I don't know this for certain, but it's the only pattern I can see: I've
run qemu on a bunch of laptops and servers over the past 12 months --
often with the exact same image and exact same commands -- and some
hosts see the guest VM use limited CPU, and others a solid 100%. This
seems to be the case whether or not -kernel-kqemu is used.
At first I thought it was an Ubuntu/Fedora Core issue, as I was running
Ubuntu on laptops and FC4 on servers (and I only saw this problem on
servers). But I just got a new Ubuntu server and the problem remains.
Now I realize there's another commonality: my servers have been
AMD-based, whereas laptops were Intel based. With this theory I looked
through the user forum and saw a strong correlation between reports of
100% CPU and AMD processors.
Is this old news or a debunked theory?
Is there some tool like CPUIdle I should be running? Any suggestions
for how to start debugging the issue?
Thanks!
-david