New: Starting a second guest with -smp 2 makes the first guest very slow and the second one hang (or also very slow)
https://bugzilla.kernel.org/show_bug.cgi?id=65081
Bug ID: 65081
Summary: Starting a second guest with -smp 2 makes the first
guest very slow and the second one hang (or also very slow)
Product: Virtualization
Version: unspecified
Kernel Version: 3.12
Hardware: All
OS: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: kvm
Assignee: [email protected]
Reporter: [email protected]
Regression: No
I think this first occured when I upgraded the kernel to 3.11 and qemu to 1.6.1. I am now running kernel version 3.12 and the problem still exists.
If I start a first KVM guest with -smp 2 it runs fine. As soon as I start another KVM guest on the same host also with -smp 2, the first one gets extremely slow. I can type one character per second via ssh. I do not see any messages from the second guest, so it seems to hang or is very slow.
If I start the second kVM guest without -smp 2 both guests seem to work fine.
I get the following messages on the host, but I do not know whether they are relevant.
kvm: SMP vm created on host with unstable TSC; guest TSC will not be reliable
qemu-system-x86: sending ioctl 5326 to a partition!
qemu-system-x86: sending ioctl 80200204 to a partition!
kvm [409]: vcpu0 unhandled rdmsr: 0xc0010001
kvm [409]: vcpu0 unhandled rdmsr: 0x3a
-
It is likely that this is not enough information to find the bug, so I would appreciate any help on what I can do to obtain more information about what might be happening here.
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[Bug 65081] Starting a second guest with -smp 2 makes the first guest very slow and the second one hang (or also very slow)
https://bugzilla.kernel.org/show_bug.cgi?id=65081
--- Comment #1 from Daniel Haid <[email protected]> ---
I have been told that I should provide the command line I am using, so here it is:
qemu-system-x86_64 -enable-kvm -kernel vmlinuz-linux -initrd initramfs-linux.img -append "console=ttyS0,57600 loglevel=7 root=/dev/vda rw" -nographic -m 512 -drive file=/dev/mapper/vg0-xxxx--root,if=virtio -drive file=/dev/mapper/vg0-xxxx--swap,if=virtio -net nic,model=virtio -net tap,name=tap0,ifname=tap0,script=no,downscript=no -smp 2
The xxxx is different for the two guests.
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[Bug 65081] Starting a second guest with -smp 2 makes the first guest very slow and the second one hang (or also very slow)
In reply to [email protected]https://bugzilla.kernel.org/show_bug.cgi?id=65081
--- Comment #2 from Daniel Haid <[email protected]> --- The problem persists with linux 3.14.1 and qemu 1.7.1.
Any suggestions on which further information you need is very welcome.
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[Bug 65081] Starting a second guest with -smp 2 makes the first guest very slow and the second one hang (or also very slow)
In reply to [email protected]https://bugzilla.kernel.org/show_bug.cgi?id=65081
--- Comment #3 from Daniel Haid <[email protected]> ---
I removed all unnecessary arguments. The following command line is actually sufficient to produce hanging guests:
qemu-system-x86_64 -enable-kvm -kernel vmlinuz-linux -initrd initramfs-linux.img -append "console=ttyS0,57600" -nographic -smp 2
I tried to run multiple guests and found out the following: It is possible to run multiple non-smp-guests (I tried three) and one smp-guest fine. But as soon as a second smp-guest is started, both smp-guests hang. However, the non-smp-guests are not affected!
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[Bug 65081] Starting a second guest with -smp 2 makes the first guest very slow and the second one hang (or also very slow)
In reply to [email protected]https://bugzilla.kernel.org/show_bug.cgi?id=65081
Daniel Haid <[email protected]> changed:
What |Removed |Added
----------------------------------------------------------------------------
Kernel Version|3.12 |3.14
--- Comment #4 from Daniel Haid <[email protected]> ---
I have now tried and seen that using -no-kvm-irqchip actually solves the problem.
Some more information about the bug:
Instead of two "-smp 2" guests, one "-smp 3" (or higher) guest will also hang.
And note that when running the two guests, they are running as different users. How can they ever be allowed to influence each other?
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[Bug 65081] Starting a second guest with -smp 2 makes the first guest very slow and the second one hang (or also very slow)
In reply to [email protected]https://bugzilla.kernel.org/show_bug.cgi?id=65081
--- Comment #5 from Daniel Haid <[email protected]> --- The problem seems to be fixed with linux 3.19 and qemu 2.2.1.
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[Bug 65081] Starting a second guest with -smp 2 makes the first guest very slow and the second one hang (or also very slow)
In reply to [email protected]https://bugzilla.kernel.org/show_bug.cgi?id=65081
Paolo Bonzini <[email protected]> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
CC| |[email protected]
Resolution|--- |CODE_FIXSignature · 2 lines
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