KVM-66: FreeBSD guest takes all CPU when idle

[Aurelien Jarno <aurelien@aurel32.net>]

Hi,

Since commit a0d22c57fbf0c67d73ab7ca3416841030e0bc22f, FreeBSD guests
takes all host CPU even when they are idle. Reverting this patch in
kvm-67 or git tree fixes (or workarounds?) the problem. Using 
-no-kvm-pit also workarounds the problem.

Some more details:
Host: Linux 2.6.24 x86-64
CPU: problem occurs on T7500 and Q9450
Guest: problem occurs with FreeBSD/i386 6.2 and 6.3

Regards,
Aurelien


commit a0d22c57fbf0c67d73ab7ca3416841030e0bc22f
Author: Marcelo Tosatti <mtosatti@redhat.com>
Date:   Fri Apr 11 14:53:26 2008 -0300

    KVM: hlt emulation should take in-kernel APIC/PIT timers into account
    
    Timers that fire between guest hlt and vcpu_block's add_wait_queue() are
    ignored, possibly resulting in hangs.
    
    Also make sure that atomic_inc and waitqueue_active tests happen in the
    specified order, otherwise the following race is open:
    
    CPU0                                        CPU1
                                                if (waitqueue_active(wq))
    add_wait_queue()
    if (!atomic_read(pit_timer->pending))
        schedule()
                                                atomic_inc(pit_timer->pending)
    
    Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
    Signed-off-by: Avi Kivity <avi@qumranet.com>


-- 
  .''`.  Aurelien Jarno	            | GPG: 1024D/F1BCDB73
 : :' :  Debian developer           | Electrical Engineer
 `. `'   aurel32@debian.org         | aurelien@aurel32.net
   `-    people.debian.org/~aurel32 | www.aurel32.net

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