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KVM: PPC: Fix issue clearing exit timing counters 

Following dump is observed on host when clearing the exit timing counters

[root@p1021mds kvm]# echo -n 'c' > vm1200_vcpu0_timing
INFO: task echo:1276 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
echo          D 0ff5bf94     0  1276   1190 0x00000000
Call Trace:
[c2157e40] [c0007908] __switch_to+0x9c/0xc4
[c2157e50] [c040293c] schedule+0x1b4/0x3bc
[c2157e90] [c04032dc] __mutex_lock_slowpath+0x74/0xc0
[c2157ec0] [c00369e4] kvmppc_init_timing_stats+0x20/0xb8
[c2157ed0] [c0036b00] kvmppc_exit_timing_write+0x84/0x98
[c2157ef0] [c00b9f90] vfs_write+0xc0/0x16c
[c2157f10] [c00ba284] sys_write+0x4c/0x90
[c2157f40] [c000e320] ret_from_syscall+0x0/0x3c

        The vcpu->mutex is used by kvm_ioctl_* (KVM_RUN etc) and same was
used when clearing the stats (in kvmppc_init_timing_stats()). What happens
is that when the guest is idle then it held the vcpu->mutx. While the
exiting timing process waits for guest to release the vcpu->mutex and
a hang state is reached.

        Now using seprate lock for exit timing stats.

Signed-off-by: Bharat Bhushan <Bharat.Bhushan@freescale.com>
Acked-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Bharat Bhushan 2011-03-25 10:32:13 +05:30 committed by Avi Kivity
parent 7c5625227f
commit 09000adb86
3 changed files with 12 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/powerpc/include/asm/kvm_host.h
View File

@ -255,6 +255,7 @@ struct kvm_vcpu_arch {
u32 dbsr;
#ifdef CONFIG_KVM_EXIT_TIMING
struct mutex exit_timing_lock;
struct kvmppc_exit_timing timing_exit;
struct kvmppc_exit_timing timing_last_enter;
u32 last_exit_type;

4
arch/powerpc/kvm/powerpc.c
View File

@ -284,6 +284,10 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
tasklet_init(&vcpu->arch.tasklet, kvmppc_decrementer_func, (ulong)vcpu);
vcpu->arch.dec_timer.function = kvmppc_decrementer_wakeup;
#ifdef CONFIG_KVM_EXIT_TIMING
mutex_init(&vcpu->arch.exit_timing_lock);
#endif
return 0;
}

10
arch/powerpc/kvm/timing.c
View File

@ -34,8 +34,8 @@ void kvmppc_init_timing_stats(struct kvm_vcpu *vcpu)
{
int i;
/* pause guest execution to avoid concurrent updates */
mutex_lock(&vcpu->mutex);
/* Take a lock to avoid concurrent updates */
mutex_lock(&vcpu->arch.exit_timing_lock);
vcpu->arch.last_exit_type = 0xDEAD;
for (i = 0; i < __NUMBER_OF_KVM_EXIT_TYPES; i++) {
@ -49,7 +49,7 @@ void kvmppc_init_timing_stats(struct kvm_vcpu *vcpu)
vcpu->arch.timing_exit.tv64 = 0;
vcpu->arch.timing_last_enter.tv64 = 0;
mutex_unlock(&vcpu->mutex);
mutex_unlock(&vcpu->arch.exit_timing_lock);
}
static void add_exit_timing(struct kvm_vcpu *vcpu, u64 duration, int type)
@ -65,6 +65,8 @@ static void add_exit_timing(struct kvm_vcpu *vcpu, u64 duration, int type)
return;
}
mutex_lock(&vcpu->arch.exit_timing_lock);
vcpu->arch.timing_count_type[type]++;
/* sum */
@ -93,6 +95,8 @@ static void add_exit_timing(struct kvm_vcpu *vcpu, u64 duration, int type)
vcpu->arch.timing_min_duration[type] = duration;
if (unlikely(duration > vcpu->arch.timing_max_duration[type]))
vcpu->arch.timing_max_duration[type] = duration;
mutex_unlock(&vcpu->arch.exit_timing_lock);
}
void kvmppc_update_timing_stats(struct kvm_vcpu *vcpu)