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authorGleb Natapov <gleb@redhat.com>2012-05-02 15:04:02 +0300
committerAvi Kivity <avi@redhat.com>2012-05-06 15:00:02 +0300
commit62c49cc976af84cb0ffcb5ec07ee88da1a94e222 (patch)
treeca69666e0c8c9854a27dcc1bd64f23a9222e72ce /arch
parenta4fa16353108431e7cfdfc3ecf683bac21b50755 (diff)
KVM: Do not take reference to mm during async #PF
It turned to be totally unneeded. The reason the code was introduced is so that KVM can prefault swapped in page, but prefault can fail even if mm is pinned since page table can change anyway. KVM handles this situation correctly though and does not inject spurious page faults. Fixes: "INFO: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected" warning while running LTP inside a KVM guest using the recent -next kernel. Reported-by: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/kvm.c9
1 files changed, 1 insertions, 8 deletions
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index b8ba6e4a27e..e554e5ad2fe 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -79,7 +79,6 @@ struct kvm_task_sleep_node {
u32 token;
int cpu;
bool halted;
- struct mm_struct *mm;
};
static struct kvm_task_sleep_head {
@@ -126,9 +125,7 @@ void kvm_async_pf_task_wait(u32 token)
n.token = token;
n.cpu = smp_processor_id();
- n.mm = current->active_mm;
n.halted = idle || preempt_count() > 1;
- atomic_inc(&n.mm->mm_count);
init_waitqueue_head(&n.wq);
hlist_add_head(&n.link, &b->list);
spin_unlock(&b->lock);
@@ -161,9 +158,6 @@ EXPORT_SYMBOL_GPL(kvm_async_pf_task_wait);
static void apf_task_wake_one(struct kvm_task_sleep_node *n)
{
hlist_del_init(&n->link);
- if (!n->mm)
- return;
- mmdrop(n->mm);
if (n->halted)
smp_send_reschedule(n->cpu);
else if (waitqueue_active(&n->wq))
@@ -207,7 +201,7 @@ again:
* async PF was not yet handled.
* Add dummy entry for the token.
*/
- n = kmalloc(sizeof(*n), GFP_ATOMIC);
+ n = kzalloc(sizeof(*n), GFP_ATOMIC);
if (!n) {
/*
* Allocation failed! Busy wait while other cpu
@@ -219,7 +213,6 @@ again:
}
n->token = token;
n->cpu = smp_processor_id();
- n->mm = NULL;
init_waitqueue_head(&n->wq);
hlist_add_head(&n->link, &b->list);
} else