aboutsummaryrefslogtreecommitdiff
path: root/arch
diff options
context:
space:
mode:
authorMarcelo Tosatti <mtosatti@redhat.com>2013-03-18 13:54:32 -0300
committerMarcelo Tosatti <mtosatti@redhat.com>2013-03-18 18:03:39 -0300
commitc09664bb44184b3846e8c5254db4eae4b932682a (patch)
treee37f7b8a0840008d3bb4f73f79ee71f4cf8df6c3 /arch
parentf445f11eb2cc265dd47da5b2e864df46cd6e5a82 (diff)
downloadlinux-linaro-stable-c09664bb44184b3846e8c5254db4eae4b932682a.tar.gz
KVM: x86: fix deadlock in clock-in-progress request handling
There is a deadlock in pvclock handling: cpu0: cpu1: kvm_gen_update_masterclock() kvm_guest_time_update() spin_lock(pvclock_gtod_sync_lock) local_irq_save(flags) spin_lock(pvclock_gtod_sync_lock) kvm_make_mclock_inprogress_request(kvm) make_all_cpus_request() smp_call_function_many() Now if smp_call_function_many() called by cpu0 tries to call function on cpu1 there will be a deadlock. Fix by moving pvclock_gtod_sync_lock protected section outside irq disabled section. Analyzed by Gleb Natapov <gleb@redhat.com> Acked-by: Gleb Natapov <gleb@redhat.com> Reported-and-Tested-by: Yongjie Ren <yongjie.ren@intel.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/x86.c18
1 files changed, 9 insertions, 9 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f71500af1f81..f7c850b36910 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1416,15 +1416,6 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
kernel_ns = 0;
host_tsc = 0;
- /* Keep irq disabled to prevent changes to the clock */
- local_irq_save(flags);
- this_tsc_khz = __get_cpu_var(cpu_tsc_khz);
- if (unlikely(this_tsc_khz == 0)) {
- local_irq_restore(flags);
- kvm_make_request(KVM_REQ_CLOCK_UPDATE, v);
- return 1;
- }
-
/*
* If the host uses TSC clock, then passthrough TSC as stable
* to the guest.
@@ -1436,6 +1427,15 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
kernel_ns = ka->master_kernel_ns;
}
spin_unlock(&ka->pvclock_gtod_sync_lock);
+
+ /* Keep irq disabled to prevent changes to the clock */
+ local_irq_save(flags);
+ this_tsc_khz = __get_cpu_var(cpu_tsc_khz);
+ if (unlikely(this_tsc_khz == 0)) {
+ local_irq_restore(flags);
+ kvm_make_request(KVM_REQ_CLOCK_UPDATE, v);
+ return 1;
+ }
if (!use_master_clock) {
host_tsc = native_read_tsc();
kernel_ns = get_kernel_ns();