* [PATCH v2 1/5] hw/virtio: Document virtio_queue_packed_empty_rcu is called within RCU
2021-09-02 16:50 [PATCH v2 0/5] hw/virtio: Minor housekeeping patches Philippe Mathieu-Daudé
@ 2021-09-02 16:50 ` Philippe Mathieu-Daudé
2021-09-02 16:50 ` [PATCH v2 2/5] hw/virtio: Comment virtqueue_flush() must be called with RCU read lock Philippe Mathieu-Daudé
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: Philippe Mathieu-Daudé @ 2021-09-02 16:50 UTC (permalink / raw)
To: qemu-devel
Cc: Michael S. Tsirkin, Jason Wang, Cornelia Huck, Stefan Hajnoczi,
Paolo Bonzini, Philippe Mathieu-Daudé,
Stefano Garzarella
While virtio_queue_packed_empty_rcu() uses the '_rcu' suffix,
it is not obvious it is called within rcu_read_lock(). All other
functions from this file called with the RCU locked have a comment
describing it. Document this one similarly for consistency.
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
hw/virtio/virtio.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 874377f37a7..a5214bca612 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -634,6 +634,7 @@ static int virtio_queue_split_empty(VirtQueue *vq)
return empty;
}
+/* Called within rcu_read_lock(). */
static int virtio_queue_packed_empty_rcu(VirtQueue *vq)
{
struct VRingPackedDesc desc;
--
2.31.1
^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH v2 2/5] hw/virtio: Comment virtqueue_flush() must be called with RCU read lock
2021-09-02 16:50 [PATCH v2 0/5] hw/virtio: Minor housekeeping patches Philippe Mathieu-Daudé
2021-09-02 16:50 ` [PATCH v2 1/5] hw/virtio: Document virtio_queue_packed_empty_rcu is called within RCU Philippe Mathieu-Daudé
@ 2021-09-02 16:50 ` Philippe Mathieu-Daudé
2021-09-02 16:50 ` [PATCH v2 3/5] hw/virtio: Remove NULL check in virtio_free_region_cache() Philippe Mathieu-Daudé
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: Philippe Mathieu-Daudé @ 2021-09-02 16:50 UTC (permalink / raw)
To: qemu-devel
Cc: Michael S. Tsirkin, Jason Wang, Cornelia Huck, Stefan Hajnoczi,
Paolo Bonzini, Philippe Mathieu-Daudé,
Stefano Garzarella
Reported-by: Stefano Garzarella <sgarzare@redhat.com>
Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
include/hw/virtio/virtio.h | 7 +++++++
hw/virtio/virtio.c | 1 +
2 files changed, 8 insertions(+)
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 8bab9cfb750..c1c5f6e53c8 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -186,6 +186,13 @@ void virtio_delete_queue(VirtQueue *vq);
void virtqueue_push(VirtQueue *vq, const VirtQueueElement *elem,
unsigned int len);
+/**
+ * virtqueue_flush:
+ * @vq: The #VirtQueue
+ * @count: Number of elements to flush
+ *
+ * Must be called within RCU critical section.
+ */
void virtqueue_flush(VirtQueue *vq, unsigned int count);
void virtqueue_detach_element(VirtQueue *vq, const VirtQueueElement *elem,
unsigned int len);
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index a5214bca612..b37344bb5e1 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -898,6 +898,7 @@ static void virtqueue_packed_flush(VirtQueue *vq, unsigned int count)
}
}
+/* Called within rcu_read_lock(). */
void virtqueue_flush(VirtQueue *vq, unsigned int count)
{
if (virtio_device_disabled(vq->vdev)) {
--
2.31.1
^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH v2 3/5] hw/virtio: Remove NULL check in virtio_free_region_cache()
2021-09-02 16:50 [PATCH v2 0/5] hw/virtio: Minor housekeeping patches Philippe Mathieu-Daudé
2021-09-02 16:50 ` [PATCH v2 1/5] hw/virtio: Document virtio_queue_packed_empty_rcu is called within RCU Philippe Mathieu-Daudé
2021-09-02 16:50 ` [PATCH v2 2/5] hw/virtio: Comment virtqueue_flush() must be called with RCU read lock Philippe Mathieu-Daudé
@ 2021-09-02 16:50 ` Philippe Mathieu-Daudé
2021-09-02 16:50 ` [PATCH v2 4/5] hw/virtio: Acquire RCU read lock in virtqueue_packed_drop_all() Philippe Mathieu-Daudé
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: Philippe Mathieu-Daudé @ 2021-09-02 16:50 UTC (permalink / raw)
To: qemu-devel
Cc: Michael S. Tsirkin, Jason Wang, Cornelia Huck, Stefan Hajnoczi,
Paolo Bonzini, Philippe Mathieu-Daudé,
Stefano Garzarella
virtio_free_region_cache() is called within call_rcu(),
always with a non-NULL argument. Ensure new code keep it
that way by replacing the NULL check by an assertion.
Add a comment this function is called within call_rcu().
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
Worth mentioning the left-over from c611c76417f?
("virtio: add MemoryListener to cache ring translations")
---
hw/virtio/virtio.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index b37344bb5e1..97f60017466 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -133,12 +133,10 @@ struct VirtQueue
QLIST_ENTRY(VirtQueue) node;
};
+/* Called within call_rcu(). */
static void virtio_free_region_cache(VRingMemoryRegionCaches *caches)
{
- if (!caches) {
- return;
- }
-
+ assert(caches != NULL);
address_space_cache_destroy(&caches->desc);
address_space_cache_destroy(&caches->avail);
address_space_cache_destroy(&caches->used);
--
2.31.1
^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH v2 4/5] hw/virtio: Acquire RCU read lock in virtqueue_packed_drop_all()
2021-09-02 16:50 [PATCH v2 0/5] hw/virtio: Minor housekeeping patches Philippe Mathieu-Daudé
` (2 preceding siblings ...)
2021-09-02 16:50 ` [PATCH v2 3/5] hw/virtio: Remove NULL check in virtio_free_region_cache() Philippe Mathieu-Daudé
@ 2021-09-02 16:50 ` Philippe Mathieu-Daudé
2021-09-02 16:50 ` [PATCH v2 5/5] hw/virtio: Have virtqueue_get_avail_bytes() pass caches arg to callees Philippe Mathieu-Daudé
2021-09-05 15:12 ` [PATCH v2 0/5] hw/virtio: Minor housekeeping patches Michael S. Tsirkin
5 siblings, 0 replies; 7+ messages in thread
From: Philippe Mathieu-Daudé @ 2021-09-02 16:50 UTC (permalink / raw)
To: qemu-devel
Cc: Michael S. Tsirkin, Jason Wang, Cornelia Huck, Stefan Hajnoczi,
Paolo Bonzini, Philippe Mathieu-Daudé,
Stefano Garzarella
vring_get_region_caches() must be called with the RCU read lock
acquired. virtqueue_packed_drop_all() does not, and uses the
'caches' pointer. Fix that by using the RCU_READ_LOCK_GUARD()
macro.
Reported-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
hw/virtio/virtio.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 97f60017466..7d3bf9091ee 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1704,6 +1704,8 @@ static unsigned int virtqueue_packed_drop_all(VirtQueue *vq)
VirtIODevice *vdev = vq->vdev;
VRingPackedDesc desc;
+ RCU_READ_LOCK_GUARD();
+
caches = vring_get_region_caches(vq);
if (!caches) {
return 0;
--
2.31.1
^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH v2 5/5] hw/virtio: Have virtqueue_get_avail_bytes() pass caches arg to callees
2021-09-02 16:50 [PATCH v2 0/5] hw/virtio: Minor housekeeping patches Philippe Mathieu-Daudé
` (3 preceding siblings ...)
2021-09-02 16:50 ` [PATCH v2 4/5] hw/virtio: Acquire RCU read lock in virtqueue_packed_drop_all() Philippe Mathieu-Daudé
@ 2021-09-02 16:50 ` Philippe Mathieu-Daudé
2021-09-05 15:12 ` [PATCH v2 0/5] hw/virtio: Minor housekeeping patches Michael S. Tsirkin
5 siblings, 0 replies; 7+ messages in thread
From: Philippe Mathieu-Daudé @ 2021-09-02 16:50 UTC (permalink / raw)
To: qemu-devel
Cc: Michael S. Tsirkin, Jason Wang, Cornelia Huck, Stefan Hajnoczi,
Paolo Bonzini, Philippe Mathieu-Daudé,
Stefano Garzarella
Both virtqueue_packed_get_avail_bytes() and
virtqueue_split_get_avail_bytes() access the region cache, but
their caller also does. Simplify by having virtqueue_get_avail_bytes
calling both with RCU lock held, and passing the caches as argument.
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
hw/virtio/virtio.c | 29 ++++++++++++-----------------
1 file changed, 12 insertions(+), 17 deletions(-)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 7d3bf9091ee..0dbfb53e51b 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -985,28 +985,23 @@ static int virtqueue_split_read_next_desc(VirtIODevice *vdev, VRingDesc *desc,
return VIRTQUEUE_READ_DESC_MORE;
}
+/* Called within rcu_read_lock(). */
static void virtqueue_split_get_avail_bytes(VirtQueue *vq,
unsigned int *in_bytes, unsigned int *out_bytes,
- unsigned max_in_bytes, unsigned max_out_bytes)
+ unsigned max_in_bytes, unsigned max_out_bytes,
+ VRingMemoryRegionCaches *caches)
{
VirtIODevice *vdev = vq->vdev;
unsigned int max, idx;
unsigned int total_bufs, in_total, out_total;
- VRingMemoryRegionCaches *caches;
MemoryRegionCache indirect_desc_cache = MEMORY_REGION_CACHE_INVALID;
int64_t len = 0;
int rc;
- RCU_READ_LOCK_GUARD();
-
idx = vq->last_avail_idx;
total_bufs = in_total = out_total = 0;
max = vq->vring.num;
- caches = vring_get_region_caches(vq);
- if (!caches) {
- goto err;
- }
while ((rc = virtqueue_num_heads(vq, idx)) > 0) {
MemoryRegionCache *desc_cache = &caches->desc;
@@ -1125,32 +1120,28 @@ static int virtqueue_packed_read_next_desc(VirtQueue *vq,
return VIRTQUEUE_READ_DESC_MORE;
}
+/* Called within rcu_read_lock(). */
static void virtqueue_packed_get_avail_bytes(VirtQueue *vq,
unsigned int *in_bytes,
unsigned int *out_bytes,
unsigned max_in_bytes,
- unsigned max_out_bytes)
+ unsigned max_out_bytes,
+ VRingMemoryRegionCaches *caches)
{
VirtIODevice *vdev = vq->vdev;
unsigned int max, idx;
unsigned int total_bufs, in_total, out_total;
MemoryRegionCache *desc_cache;
- VRingMemoryRegionCaches *caches;
MemoryRegionCache indirect_desc_cache = MEMORY_REGION_CACHE_INVALID;
int64_t len = 0;
VRingPackedDesc desc;
bool wrap_counter;
- RCU_READ_LOCK_GUARD();
idx = vq->last_avail_idx;
wrap_counter = vq->last_avail_wrap_counter;
total_bufs = in_total = out_total = 0;
max = vq->vring.num;
- caches = vring_get_region_caches(vq);
- if (!caches) {
- goto err;
- }
for (;;) {
unsigned int num_bufs = total_bufs;
@@ -1251,6 +1242,8 @@ void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes,
uint16_t desc_size;
VRingMemoryRegionCaches *caches;
+ RCU_READ_LOCK_GUARD();
+
if (unlikely(!vq->vring.desc)) {
goto err;
}
@@ -1269,10 +1262,12 @@ void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes,
if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) {
virtqueue_packed_get_avail_bytes(vq, in_bytes, out_bytes,
- max_in_bytes, max_out_bytes);
+ max_in_bytes, max_out_bytes,
+ caches);
} else {
virtqueue_split_get_avail_bytes(vq, in_bytes, out_bytes,
- max_in_bytes, max_out_bytes);
+ max_in_bytes, max_out_bytes,
+ caches);
}
return;
--
2.31.1
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH v2 0/5] hw/virtio: Minor housekeeping patches
2021-09-02 16:50 [PATCH v2 0/5] hw/virtio: Minor housekeeping patches Philippe Mathieu-Daudé
` (4 preceding siblings ...)
2021-09-02 16:50 ` [PATCH v2 5/5] hw/virtio: Have virtqueue_get_avail_bytes() pass caches arg to callees Philippe Mathieu-Daudé
@ 2021-09-05 15:12 ` Michael S. Tsirkin
5 siblings, 0 replies; 7+ messages in thread
From: Michael S. Tsirkin @ 2021-09-05 15:12 UTC (permalink / raw)
To: Philippe Mathieu-Daudé
Cc: Jason Wang, Cornelia Huck, qemu-devel, Stefan Hajnoczi,
Paolo Bonzini, Stefano Garzarella
On Thu, Sep 02, 2021 at 06:50:34PM +0200, Philippe Mathieu-Daudé wrote:
> Hi,
>
> This series contains few patches I gathered while tooking notes
> trying to understand issues #300-#302.
v1 was includes in my pull request already, pls send
incremental patches on top. Thanks!
> Since v1:
> - Added virtqueue_flush comment (Stefano)
> - Call RCU_READ_LOCK_GUARD in virtqueue_packed_drop_all (Stefano)
>
> Philippe Mathieu-Daudé (5):
> hw/virtio: Document virtio_queue_packed_empty_rcu is called within RCU
> hw/virtio: Comment virtqueue_flush() must be called with RCU read lock
> hw/virtio: Remove NULL check in virtio_free_region_cache()
> hw/virtio: Acquire RCU read lock in virtqueue_packed_drop_all()
> hw/virtio: Have virtqueue_get_avail_bytes() pass caches arg to callees
>
> include/hw/virtio/virtio.h | 7 +++++++
> hw/virtio/virtio.c | 39 ++++++++++++++++++--------------------
> 2 files changed, 25 insertions(+), 21 deletions(-)
>
> --
> 2.31.1
>
^ permalink raw reply [flat|nested] 7+ messages in thread