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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 2 of 3] RFC: mem_event: use wait queue when ring is full
# HG changeset patch
# User Olaf Hering <olaf@xxxxxxxxx>
# Date 1321996145 -3600
# Node ID de6860cb9205b68d1287482288d1b7b9d0255609
# Parent d347a8a36d2e7951f98a3d22866dce004484d95f
RFC: mem_event: use wait queue when ring is full
CAUTION: while the patch by itself is supposed to be complete,
the added usage of waitqueues will lead to sudden host reboots!
This change is based on an idea/patch from Adin Scannell.
If the ring is full, put the current vcpu to sleep if it belongs to the
target domain. The wakeup happens in the p2m_*_resume functions.
A request from another domain will use the existing ->req_producers
functionality because sleeping is not possible if the vcpu does not
belong to the target domain.
This change fixes also a bug in p2m_mem_paging_drop_page(). Up to now a
full ring will lead to harmless inconsistency in the pager,
v2:
- p2m_mem_paging_populate: move vcpu_pause after put_request, otherwise the
vcpu will not wake_up after a wait_event because the pause_count was
increased twice. Fixes guest hangs.
- update free space check in _mem_event_put_request()
- simplify mem_event_put_request()
Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
diff -r d347a8a36d2e -r de6860cb9205 xen/arch/x86/hvm/hvm.c
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -4099,7 +4099,7 @@ static int hvm_memory_event_traps(long p
return 1;
rc = mem_event_check_ring(d, &d->mem_event->mem_access);
- if ( rc )
+ if ( rc < 0 )
return rc;
memset(&req, 0, sizeof(req));
diff -r d347a8a36d2e -r de6860cb9205 xen/arch/x86/mm/mem_event.c
--- a/xen/arch/x86/mm/mem_event.c
+++ b/xen/arch/x86/mm/mem_event.c
@@ -23,6 +23,7 @@
#include <asm/domain.h>
#include <xen/event.h>
+#include <xen/wait.h>
#include <asm/p2m.h>
#include <asm/mem_event.h>
#include <asm/mem_paging.h>
@@ -39,6 +40,7 @@
static int mem_event_enable(struct domain *d,
xen_domctl_mem_event_op_t *mec,
+ int mem_event_bit,
struct mem_event_domain *med)
{
int rc;
@@ -107,8 +109,12 @@ static int mem_event_enable(struct domai
mem_event_ring_lock_init(med);
+ med->mem_event_bit = mem_event_bit;
+
+ init_waitqueue_head(&med->wq);
+
/* Wake any VCPUs paused for memory events */
- mem_event_unpause_vcpus(d);
+ mem_event_unpause_vcpus(d, med);
return 0;
@@ -124,6 +130,9 @@ static int mem_event_enable(struct domai
static int mem_event_disable(struct mem_event_domain *med)
{
+ if (!list_empty(&med->wq.list))
+ return -EBUSY;
+
unmap_domain_page(med->ring_page);
med->ring_page = NULL;
@@ -133,13 +142,21 @@ static int mem_event_disable(struct mem_
return 0;
}
-void mem_event_put_request(struct domain *d, struct mem_event_domain *med,
mem_event_request_t *req)
+static int _mem_event_put_request(struct domain *d, struct mem_event_domain
*med, mem_event_request_t *req)
{
mem_event_front_ring_t *front_ring;
+ int free_requests;
RING_IDX req_prod;
mem_event_ring_lock(med);
+ free_requests = RING_FREE_REQUESTS(&med->front_ring);
+ /* A request was eventually claimed in mem_event_check_ring() */
+ if ((current->domain == d && free_requests <= med->req_producers) ||
!free_requests) {
+ mem_event_ring_unlock(med);
+ return 0;
+ }
+
front_ring = &med->front_ring;
req_prod = front_ring->req_prod_pvt;
@@ -155,6 +172,20 @@ void mem_event_put_request(struct domain
mem_event_ring_unlock(med);
notify_via_xen_event_channel(d, med->xen_port);
+
+ return 1;
+}
+
+void mem_event_put_request(struct domain *d, struct mem_event_domain *med,
mem_event_request_t *req)
+{
+ /* Go to sleep if request came from guest */
+ if (current->domain == d) {
+ wait_event(med->wq, _mem_event_put_request(d, med, req));
+ return;
+ }
+ /* Ring was full anyway, unable to sleep in non-guest context */
+ if (!_mem_event_put_request(d, med, req))
+ printk("Failed to put memreq: d %u t %x f %x gfn %lx\n", d->domain_id,
req->type, req->flags, (unsigned long)req->gfn);
}
void mem_event_get_response(struct mem_event_domain *med, mem_event_response_t
*rsp)
@@ -178,21 +209,27 @@ void mem_event_get_response(struct mem_e
mem_event_ring_unlock(med);
}
-void mem_event_unpause_vcpus(struct domain *d)
+void mem_event_unpause_vcpus(struct domain *d, struct mem_event_domain *med)
{
struct vcpu *v;
for_each_vcpu ( d, v )
- if ( test_and_clear_bit(_VPF_mem_event, &v->pause_flags) )
+ if ( test_and_clear_bit(med->mem_event_bit, &v->pause_flags) )
vcpu_wake(v);
}
-void mem_event_mark_and_pause(struct vcpu *v)
+void mem_event_mark_and_pause(struct vcpu *v, struct mem_event_domain *med)
{
- set_bit(_VPF_mem_event, &v->pause_flags);
+ set_bit(med->mem_event_bit, &v->pause_flags);
vcpu_sleep_nosync(v);
}
+/**
+ * mem_event_put_req_producers - Release a claimed slot
+ * @med: mem_event ring
+ *
+ * mem_event_put_req_producers() releases a claimed slot in the mem_event ring.
+ */
void mem_event_put_req_producers(struct mem_event_domain *med)
{
mem_event_ring_lock(med);
@@ -200,9 +237,26 @@ void mem_event_put_req_producers(struct
mem_event_ring_unlock(med);
}
+/**
+ * mem_event_check_ring - Check state of a mem_event ring
+ * @d: guest domain
+ * @med: mem_event ring
+ *
+ * Return codes: < 0: the ring is not yet configured
+ * 0: the ring has some room
+ * > 0: the ring is full
+ *
+ * mem_event_check_ring() checks the state of the given mem_event ring.
+ * If the current vcpu belongs to the guest domain, the function assumes that
+ * mem_event_put_request() will sleep until the ring has room again.
+ *
+ * If the current vcpu does not belong to the target domain the caller must try
+ * again until there is room. A slot is claimed and the caller can place a
+ * request. If the caller does not need to send a request, the claimed slot has
+ * to be released with mem_event_put_req_producers().
+ */
int mem_event_check_ring(struct domain *d, struct mem_event_domain *med)
{
- struct vcpu *curr = current;
int free_requests;
int ring_full = 1;
@@ -218,8 +272,8 @@ int mem_event_check_ring(struct domain *
ring_full = 0;
}
- if ( ring_full && (curr->domain == d) )
- mem_event_mark_and_pause(curr);
+ if ( current->domain == d )
+ ring_full = 0;
mem_event_ring_unlock(med);
@@ -287,7 +341,7 @@ int mem_event_domctl(struct domain *d, x
if ( p2m->pod.entry_count )
break;
- rc = mem_event_enable(d, mec, med);
+ rc = mem_event_enable(d, mec, _VPF_me_mem_paging, med);
}
break;
@@ -326,7 +380,7 @@ int mem_event_domctl(struct domain *d, x
if ( boot_cpu_data.x86_vendor != X86_VENDOR_INTEL )
break;
- rc = mem_event_enable(d, mec, med);
+ rc = mem_event_enable(d, mec, _VPF_me_mem_access, med);
}
break;
diff -r d347a8a36d2e -r de6860cb9205 xen/arch/x86/mm/mem_sharing.c
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -253,19 +253,11 @@ static void mem_sharing_audit(void)
#endif
-static struct page_info* mem_sharing_alloc_page(struct domain *d,
- unsigned long gfn)
+static void mem_sharing_notify_helper(struct domain *d, unsigned long gfn)
{
- struct page_info* page;
struct vcpu *v = current;
mem_event_request_t req;
- page = alloc_domheap_page(d, 0);
- if(page != NULL) return page;
-
- memset(&req, 0, sizeof(req));
- req.type = MEM_EVENT_TYPE_SHARED;
-
if ( v->domain != d )
{
/* XXX This path needs some attention. For now, just fail foreign
@@ -275,20 +267,20 @@ static struct page_info* mem_sharing_all
gdprintk(XENLOG_ERR,
"Failed alloc on unshare path for foreign (%d) lookup\n",
d->domain_id);
- return page;
+ return;
}
- vcpu_pause_nosync(v);
- req.flags |= MEM_EVENT_FLAG_VCPU_PAUSED;
+ if (mem_event_check_ring(d, &d->mem_event->mem_share) < 0)
+ return;
- if(mem_event_check_ring(d, &d->mem_event->mem_share)) return page;
-
+ memset(&req, 0, sizeof(req));
+ req.type = MEM_EVENT_TYPE_SHARED;
+ req.flags = MEM_EVENT_FLAG_VCPU_PAUSED;
req.gfn = gfn;
req.p2mt = p2m_ram_shared;
req.vcpu_id = v->vcpu_id;
mem_event_put_request(d, &d->mem_event->mem_share, &req);
-
- return page;
+ vcpu_pause_nosync(v);
}
unsigned int mem_sharing_get_nr_saved_mfns(void)
@@ -653,7 +645,7 @@ gfn_found:
if(ret == 0) goto private_page_found;
old_page = page;
- page = mem_sharing_alloc_page(d, gfn);
+ page = alloc_domheap_page(d, 0);
if(!page)
{
/* We've failed to obtain memory for private page. Need to re-add the
@@ -661,6 +653,7 @@ gfn_found:
list_add(&gfn_info->list, &hash_entry->gfns);
put_gfn(d, gfn);
shr_unlock();
+ mem_sharing_notify_helper(d, gfn);
return -ENOMEM;
}
diff -r d347a8a36d2e -r de6860cb9205 xen/arch/x86/mm/p2m.c
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -884,17 +884,13 @@ void p2m_mem_paging_drop_page(struct dom
struct vcpu *v = current;
mem_event_request_t req;
- /* Check that there's space on the ring for this request */
- if ( mem_event_check_ring(d, &d->mem_event->mem_paging) == 0)
- {
- /* Send release notification to pager */
- memset(&req, 0, sizeof(req));
- req.flags |= MEM_EVENT_FLAG_DROP_PAGE;
- req.gfn = gfn;
- req.vcpu_id = v->vcpu_id;
+ /* Send release notification to pager */
+ memset(&req, 0, sizeof(req));
+ req.flags = MEM_EVENT_FLAG_DROP_PAGE;
+ req.gfn = gfn;
+ req.vcpu_id = v->vcpu_id;
- mem_event_put_request(d, &d->mem_event->mem_paging, &req);
- }
+ mem_event_put_request(d, &d->mem_event->mem_paging, &req);
}
/**
@@ -952,7 +948,6 @@ void p2m_mem_paging_populate(struct doma
/* Pause domain if request came from guest and gfn has paging type */
if ( p2m_is_paging(p2mt) && v->domain == d )
{
- vcpu_pause_nosync(v);
req.flags |= MEM_EVENT_FLAG_VCPU_PAUSED;
}
/* No need to inform pager if the gfn is not in the page-out path */
@@ -969,6 +964,10 @@ void p2m_mem_paging_populate(struct doma
req.vcpu_id = v->vcpu_id;
mem_event_put_request(d, &d->mem_event->mem_paging, &req);
+
+ /* Pause guest after put_request to allow wake_up after wait_event */
+ if ( req.flags & MEM_EVENT_FLAG_VCPU_PAUSED )
+ vcpu_pause_nosync(v);
}
/**
@@ -1071,8 +1070,8 @@ void p2m_mem_paging_resume(struct domain
if ( rsp.flags & MEM_EVENT_FLAG_VCPU_PAUSED )
vcpu_unpause(d->vcpu[rsp.vcpu_id]);
- /* Unpause any domains that were paused because the ring was full */
- mem_event_unpause_vcpus(d);
+ /* Unpause all vcpus that were paused because the ring was full */
+ wake_up(&d->mem_event->mem_paging.wq);
}
void p2m_mem_access_check(unsigned long gpa, bool_t gla_valid, unsigned long
gla,
@@ -1111,7 +1110,7 @@ void p2m_mem_access_check(unsigned long
"Memory access permissions failure, no mem_event listener:
pausing VCPU %d, dom %d\n",
v->vcpu_id, d->domain_id);
- mem_event_mark_and_pause(v);
+ mem_event_mark_and_pause(v, &d->mem_event->mem_access);
}
else
{
@@ -1131,8 +1130,7 @@ void p2m_mem_access_check(unsigned long
req.reason = MEM_EVENT_REASON_VIOLATION;
/* Pause the current VCPU unconditionally */
- vcpu_pause_nosync(v);
- req.flags |= MEM_EVENT_FLAG_VCPU_PAUSED;
+ req.flags = MEM_EVENT_FLAG_VCPU_PAUSED;
/* Send request to mem event */
req.gfn = gfn;
@@ -1148,6 +1146,7 @@ void p2m_mem_access_check(unsigned long
mem_event_put_request(d, &d->mem_event->mem_access, &req);
/* VCPU paused, mem event request sent */
+ vcpu_pause_nosync(v);
}
void p2m_mem_access_resume(struct p2m_domain *p2m)
@@ -1161,9 +1160,11 @@ void p2m_mem_access_resume(struct p2m_do
if ( rsp.flags & MEM_EVENT_FLAG_VCPU_PAUSED )
vcpu_unpause(d->vcpu[rsp.vcpu_id]);
- /* Unpause any domains that were paused because the ring was full or no
listener
- * was available */
- mem_event_unpause_vcpus(d);
+ /* Wakeup all vcpus waiting because the ring was full */
+ wake_up(&d->mem_event->mem_access.wq);
+
+ /* Unpause all vcpus that were paused because no listener was available */
+ mem_event_unpause_vcpus(d, &d->mem_event->mem_access);
}
diff -r d347a8a36d2e -r de6860cb9205 xen/include/asm-x86/mem_event.h
--- a/xen/include/asm-x86/mem_event.h
+++ b/xen/include/asm-x86/mem_event.h
@@ -25,12 +25,12 @@
#define __MEM_EVENT_H__
/* Pauses VCPU while marking pause flag for mem event */
-void mem_event_mark_and_pause(struct vcpu *v);
+void mem_event_mark_and_pause(struct vcpu *v, struct mem_event_domain *med);
int mem_event_check_ring(struct domain *d, struct mem_event_domain *med);
void mem_event_put_req_producers(struct mem_event_domain *med);
void mem_event_put_request(struct domain *d, struct mem_event_domain *med,
mem_event_request_t *req);
void mem_event_get_response(struct mem_event_domain *med, mem_event_response_t
*rsp);
-void mem_event_unpause_vcpus(struct domain *d);
+void mem_event_unpause_vcpus(struct domain *d, struct mem_event_domain *med);
int mem_event_domctl(struct domain *d, xen_domctl_mem_event_op_t *mec,
XEN_GUEST_HANDLE(void) u_domctl);
diff -r d347a8a36d2e -r de6860cb9205 xen/include/xen/sched.h
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -14,6 +14,7 @@
#include <xen/nodemask.h>
#include <xen/radix-tree.h>
#include <xen/multicall.h>
+#include <xen/wait.h>
#include <public/xen.h>
#include <public/domctl.h>
#include <public/sysctl.h>
@@ -192,6 +193,10 @@ struct mem_event_domain
mem_event_front_ring_t front_ring;
/* event channel port (vcpu0 only) */
int xen_port;
+ /* mem_event bit for vcpu->pause_flags */
+ int mem_event_bit;
+ /* list of vcpus waiting for room in the ring */
+ struct waitqueue_head wq;
};
struct mem_event_per_domain
@@ -615,9 +620,12 @@ static inline struct domain *next_domain
/* VCPU affinity has changed: migrating to a new CPU. */
#define _VPF_migrating 3
#define VPF_migrating (1UL<<_VPF_migrating)
- /* VCPU is blocked on memory-event ring. */
-#define _VPF_mem_event 4
-#define VPF_mem_event (1UL<<_VPF_mem_event)
+ /* VCPU is blocked on mem_paging ring. */
+#define _VPF_me_mem_paging 4
+#define VPF_me_mem_paging (1UL<<_VPF_me_mem_paging)
+ /* VCPU is blocked on mem_access ring. */
+#define _VPF_me_mem_access 5
+#define VPF_me_mem_access (1UL<<_VPF_me_mem_access)
static inline int vcpu_runnable(struct vcpu *v)
{
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