# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1224758459 -3600
# Node ID 4941c5a1459839c9923f7dafe6fe7705f90ca436
# Parent 50fc79012db7b393e67cf88fda026f67990623cf
x86, hvm: Move return-to-guest timer and interrupt cranking logic
outside of IRQ-safe context. This allows us to safely take
non-IRQ-safe spinlocks.
The drawback is that {vmx,svm}_intr_assist() now races new event
notifications delivered by IRQ or IPI. We close down this race by
having vcpu_kick() send a dummy softirq -- this gets picked up in
IRQ-sage context and will cause retry of *_intr_assist(). We avoid
delivering the softirq where possible by avoiding it when we are
running in the non-IRQ context of the VCPU to be kicked.
Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
---
xen/arch/x86/domain.c | 48 ++++++++++++++++++++++++++++++++++++++++++
xen/arch/x86/hvm/svm/entry.S | 3 +-
xen/arch/x86/hvm/vmx/entry.S | 6 +++--
xen/include/asm-x86/event.h | 32 +---------------------------
xen/include/asm-x86/softirq.h | 3 +-
5 files changed, 58 insertions(+), 34 deletions(-)
diff -r 50fc79012db7 -r 4941c5a14598 xen/arch/x86/domain.c
--- a/xen/arch/x86/domain.c Thu Oct 23 11:20:44 2008 +0100
+++ b/xen/arch/x86/domain.c Thu Oct 23 11:40:59 2008 +0100
@@ -1892,6 +1892,54 @@ void domain_cpuid(
*eax = *ebx = *ecx = *edx = 0;
}
+void vcpu_kick(struct vcpu *v)
+{
+ /*
+ * NB1. 'pause_flags' and 'processor' must be checked /after/ update of
+ * pending flag. These values may fluctuate (after all, we hold no
+ * locks) but the key insight is that each change will cause
+ * evtchn_upcall_pending to be polled.
+ *
+ * NB2. We save the running flag across the unblock to avoid a needless
+ * IPI for domains that we IPI'd to unblock.
+ */
+ bool_t running = v->is_running;
+ vcpu_unblock(v);
+ if ( running && (in_irq() || (v != current)) )
+ cpu_raise_softirq(v->processor, VCPU_KICK_SOFTIRQ);
+}
+
+void vcpu_mark_events_pending(struct vcpu *v)
+{
+ int already_pending = test_and_set_bit(
+ 0, (unsigned long *)&vcpu_info(v, evtchn_upcall_pending));
+
+ if ( already_pending )
+ return;
+
+ if ( is_hvm_vcpu(v) )
+ hvm_assert_evtchn_irq(v);
+ else
+ vcpu_kick(v);
+}
+
+static void vcpu_kick_softirq(void)
+{
+ /*
+ * Nothing to do here: we merely prevent notifiers from racing with checks
+ * executed on return to guest context with interrupts enabled. See, for
+ * example, xxx_intr_assist() executed on return to HVM guest context.
+ */
+}
+
+static int __init init_vcpu_kick_softirq(void)
+{
+ open_softirq(VCPU_KICK_SOFTIRQ, vcpu_kick_softirq);
+ return 0;
+}
+__initcall(init_vcpu_kick_softirq);
+
+
/*
* Local variables:
* mode: C
diff -r 50fc79012db7 -r 4941c5a14598 xen/arch/x86/hvm/svm/entry.S
--- a/xen/arch/x86/hvm/svm/entry.S Thu Oct 23 11:20:44 2008 +0100
+++ b/xen/arch/x86/hvm/svm/entry.S Thu Oct 23 11:40:59 2008 +0100
@@ -57,6 +57,8 @@
#endif
ENTRY(svm_asm_do_resume)
+ call svm_intr_assist
+
get_current(bx)
CLGI
@@ -67,7 +69,6 @@ ENTRY(svm_asm_do_resume)
jnz .Lsvm_process_softirqs
call svm_asid_handle_vmrun
- call svm_intr_assist
cmpb $0,addr_of(tb_init_done)
jnz .Lsvm_trace
diff -r 50fc79012db7 -r 4941c5a14598 xen/arch/x86/hvm/vmx/entry.S
--- a/xen/arch/x86/hvm/vmx/entry.S Thu Oct 23 11:20:44 2008 +0100
+++ b/xen/arch/x86/hvm/vmx/entry.S Thu Oct 23 11:40:59 2008 +0100
@@ -122,6 +122,8 @@ vmx_asm_vmexit_handler:
.globl vmx_asm_do_vmentry
vmx_asm_do_vmentry:
+ call vmx_intr_assist
+
get_current(bx)
cli
@@ -130,8 +132,6 @@ vmx_asm_do_vmentry:
lea addr_of(irq_stat),r(dx)
cmpl $0,(r(dx),r(ax),1)
jnz .Lvmx_process_softirqs
-
- call vmx_intr_assist
testb $0xff,VCPU_vmx_emul(r(bx))
jnz .Lvmx_goto_realmode
@@ -179,11 +179,13 @@ vmx_asm_do_vmentry:
/*.Lvmx_resume:*/
VMRESUME
+ sti
call vm_resume_fail
ud2
.Lvmx_launch:
VMLAUNCH
+ sti
call vm_launch_fail
ud2
diff -r 50fc79012db7 -r 4941c5a14598 xen/include/asm-x86/event.h
--- a/xen/include/asm-x86/event.h Thu Oct 23 11:20:44 2008 +0100
+++ b/xen/include/asm-x86/event.h Thu Oct 23 11:40:59 2008 +0100
@@ -11,36 +11,8 @@
#include <xen/shared.h>
-static inline void vcpu_kick(struct vcpu *v)
-{
- /*
- * NB1. 'pause_flags' and 'processor' must be checked /after/ update of
- * pending flag. These values may fluctuate (after all, we hold no
- * locks) but the key insight is that each change will cause
- * evtchn_upcall_pending to be polled.
- *
- * NB2. We save the running flag across the unblock to avoid a needless
- * IPI for domains that we IPI'd to unblock.
- */
- int running = v->is_running;
- vcpu_unblock(v);
- if ( running )
- smp_send_event_check_cpu(v->processor);
-}
-
-static inline void vcpu_mark_events_pending(struct vcpu *v)
-{
- int already_pending = test_and_set_bit(
- 0, (unsigned long *)&vcpu_info(v, evtchn_upcall_pending));
-
- if ( already_pending )
- return;
-
- if ( is_hvm_vcpu(v) )
- hvm_assert_evtchn_irq(v);
- else
- vcpu_kick(v);
-}
+void vcpu_kick(struct vcpu *v);
+void vcpu_mark_events_pending(struct vcpu *v);
int hvm_local_events_need_delivery(struct vcpu *v);
static inline int local_events_need_delivery(void)
diff -r 50fc79012db7 -r 4941c5a14598 xen/include/asm-x86/softirq.h
--- a/xen/include/asm-x86/softirq.h Thu Oct 23 11:20:44 2008 +0100
+++ b/xen/include/asm-x86/softirq.h Thu Oct 23 11:40:59 2008 +0100
@@ -3,7 +3,8 @@
#define NMI_MCE_SOFTIRQ (NR_COMMON_SOFTIRQS + 0)
#define TIME_CALIBRATE_SOFTIRQ (NR_COMMON_SOFTIRQS + 1)
+#define VCPU_KICK_SOFTIRQ (NR_COMMON_SOFTIRQS + 2)
-#define NR_ARCH_SOFTIRQS 2
+#define NR_ARCH_SOFTIRQS 3
#endif /* __ASM_SOFTIRQ_H__ */
_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-changelog
|
Home