[PATCH v7 10/12] Handle async PF in non preemptable context
From: Gleb Natapov g...@redhat.com
If async page fault is received by idle task or when preemp_count is
not zero guest cannot reschedule, so do sti; hlt and wait for page to be
ready. vcpu can still process interrupts while it waits for the page to
be ready.
Acked-by: Rik van Riel r...@redhat.com
Signed-off-by: Gleb Natapov g...@redhat.com
---
arch/x86/kernel/kvm.c | 40 ++--
1 files changed, 34 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index d564063..47ea93e 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -37,6 +37,7 @@
#include asm/cpu.h
#include asm/traps.h
#include asm/desc.h
+#include asm/tlbflush.h
#define MMU_QUEUE_SIZE 1024
@@ -78,6 +79,8 @@ struct kvm_task_sleep_node {
wait_queue_head_t wq;
u32 token;
int cpu;
+ bool halted;
+ struct mm_struct *mm;
};
static struct kvm_task_sleep_head {
@@ -106,6 +109,11 @@ void kvm_async_pf_task_wait(u32 token)
struct kvm_task_sleep_head *b = async_pf_sleepers[key];
struct kvm_task_sleep_node n, *e;
DEFINE_WAIT(wait);
+ int cpu, idle;
+
+ cpu = get_cpu();
+ idle = idle_cpu(cpu);
+ put_cpu();
spin_lock(b-lock);
e = _find_apf_task(b, token);
@@ -119,19 +127,33 @@ 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);
for (;;) {
- prepare_to_wait(n.wq, wait, TASK_UNINTERRUPTIBLE);
+ if (!n.halted)
+ prepare_to_wait(n.wq, wait, TASK_UNINTERRUPTIBLE);
if (hlist_unhashed(n.link))
break;
- local_irq_enable();
- schedule();
- local_irq_disable();
+
+ if (!n.halted) {
+ local_irq_enable();
+ schedule();
+ local_irq_disable();
+ } else {
+ /*
+* We cannot reschedule. So halt.
+*/
+ native_safe_halt();
+ local_irq_disable();
+ }
}
- finish_wait(n.wq, wait);
+ if (!n.halted)
+ finish_wait(n.wq, wait);
return;
}
@@ -140,7 +162,12 @@ 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 (waitqueue_active(n-wq))
+ if (!n-mm)
+ return;
+ mmdrop(n-mm);
+ if (n-halted)
+ smp_send_reschedule(n-cpu);
+ else if (waitqueue_active(n-wq))
wake_up(n-wq);
}
@@ -193,6 +220,7 @@ 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
--
1.7.1
--
To unsubscribe from this list: send the line unsubscribe kvm in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
[PATCH v7 10/12] Handle async PF in non preemptable context
If async page fault is received by idle task or when preemp_count is
not zero guest cannot reschedule, so do sti; hlt and wait for page to be
ready. vcpu can still process interrupts while it waits for the page to
be ready.
Acked-by: Rik van Riel r...@redhat.com
Signed-off-by: Gleb Natapov g...@redhat.com
---
arch/x86/kernel/kvm.c | 40 ++--
1 files changed, 34 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index d564063..47ea93e 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -37,6 +37,7 @@
#include asm/cpu.h
#include asm/traps.h
#include asm/desc.h
+#include asm/tlbflush.h
#define MMU_QUEUE_SIZE 1024
@@ -78,6 +79,8 @@ struct kvm_task_sleep_node {
wait_queue_head_t wq;
u32 token;
int cpu;
+ bool halted;
+ struct mm_struct *mm;
};
static struct kvm_task_sleep_head {
@@ -106,6 +109,11 @@ void kvm_async_pf_task_wait(u32 token)
struct kvm_task_sleep_head *b = async_pf_sleepers[key];
struct kvm_task_sleep_node n, *e;
DEFINE_WAIT(wait);
+ int cpu, idle;
+
+ cpu = get_cpu();
+ idle = idle_cpu(cpu);
+ put_cpu();
spin_lock(b-lock);
e = _find_apf_task(b, token);
@@ -119,19 +127,33 @@ 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);
for (;;) {
- prepare_to_wait(n.wq, wait, TASK_UNINTERRUPTIBLE);
+ if (!n.halted)
+ prepare_to_wait(n.wq, wait, TASK_UNINTERRUPTIBLE);
if (hlist_unhashed(n.link))
break;
- local_irq_enable();
- schedule();
- local_irq_disable();
+
+ if (!n.halted) {
+ local_irq_enable();
+ schedule();
+ local_irq_disable();
+ } else {
+ /*
+* We cannot reschedule. So halt.
+*/
+ native_safe_halt();
+ local_irq_disable();
+ }
}
- finish_wait(n.wq, wait);
+ if (!n.halted)
+ finish_wait(n.wq, wait);
return;
}
@@ -140,7 +162,12 @@ 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 (waitqueue_active(n-wq))
+ if (!n-mm)
+ return;
+ mmdrop(n-mm);
+ if (n-halted)
+ smp_send_reschedule(n-cpu);
+ else if (waitqueue_active(n-wq))
wake_up(n-wq);
}
@@ -193,6 +220,7 @@ 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
--
1.7.1
--
To unsubscribe from this list: send the line unsubscribe kvm in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
