Merge tag 'for-linus-5.10b-rc1b-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull more xen updates from Juergen Gross:

 - A single patch to fix the Xen security issue XSA-331 (malicious
   guests can DoS dom0 by triggering NULL-pointer dereferences or access
   to stale data).

 - A larger series to fix the Xen security issue XSA-332 (malicious
   guests can DoS dom0 by sending events at high frequency leading to
   dom0's vcpus being busy in IRQ handling for elongated times).

* tag 'for-linus-5.10b-rc1b-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen/events: block rogue events for some time
  xen/events: defer eoi in case of excessive number of events
  xen/events: use a common cpu hotplug hook for event channels
  xen/events: switch user event channels to lateeoi model
  xen/pciback: use lateeoi irq binding
  xen/pvcallsback: use lateeoi irq binding
  xen/scsiback: use lateeoi irq binding
  xen/netback: use lateeoi irq binding
  xen/blkback: use lateeoi irq binding
  xen/events: add a new "late EOI" evtchn framework
  xen/events: fix race in evtchn_fifo_unmask()
  xen/events: add a proper barrier to 2-level uevent unmasking
  xen/events: avoid removing an event channel while handling it

2 files changed, 19 insertions, 8 deletions

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index adfc9352351d..501e9dacfff9 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -201,7 +201,7 @@ static inline void shrink_free_pagepool(struct xen_blkif_ring *ring, int num)
 
 #define vaddr(page) ((unsigned long)pfn_to_kaddr(page_to_pfn(page)))
 
-static int do_block_io_op(struct xen_blkif_ring *ring);
+static int do_block_io_op(struct xen_blkif_ring *ring, unsigned int *eoi_flags);
 static int dispatch_rw_block_io(struct xen_blkif_ring *ring,
 				struct blkif_request *req,
 				struct pending_req *pending_req);
@@ -612,6 +612,8 @@ int xen_blkif_schedule(void *arg)
 	struct xen_vbd *vbd = &blkif->vbd;
 	unsigned long timeout;
 	int ret;
+	bool do_eoi;
+	unsigned int eoi_flags = XEN_EOI_FLAG_SPURIOUS;
 
 	set_freezable();
 	while (!kthread_should_stop()) {
@@ -636,16 +638,23 @@ int xen_blkif_schedule(void *arg)
 		if (timeout == 0)
 			goto purge_gnt_list;
 
+		do_eoi = ring->waiting_reqs;
+
 		ring->waiting_reqs = 0;
 		smp_mb(); /* clear flag *before* checking for work */
 
-		ret = do_block_io_op(ring);
+		ret = do_block_io_op(ring, &eoi_flags);
 		if (ret > 0)
 			ring->waiting_reqs = 1;
 		if (ret == -EACCES)
 			wait_event_interruptible(ring->shutdown_wq,
 						 kthread_should_stop());
 
+		if (do_eoi && !ring->waiting_reqs) {
+			xen_irq_lateeoi(ring->irq, eoi_flags);
+			eoi_flags |= XEN_EOI_FLAG_SPURIOUS;
+		}
+
 purge_gnt_list:
 		if (blkif->vbd.feature_gnt_persistent &&
 		    time_after(jiffies, ring->next_lru)) {
@@ -1121,7 +1130,7 @@ static void end_block_io_op(struct bio *bio)
  * and transmute  it to the block API to hand it over to the proper block disk.
  */
 static int
-__do_block_io_op(struct xen_blkif_ring *ring)
+__do_block_io_op(struct xen_blkif_ring *ring, unsigned int *eoi_flags)
 {
 	union blkif_back_rings *blk_rings = &ring->blk_rings;
 	struct blkif_request req;
@@ -1144,6 +1153,9 @@ __do_block_io_op(struct xen_blkif_ring *ring)
 		if (RING_REQUEST_CONS_OVERFLOW(&blk_rings->common, rc))
 			break;
 
+		/* We've seen a request, so clear spurious eoi flag. */
+		*eoi_flags &= ~XEN_EOI_FLAG_SPURIOUS;
+
 		if (kthread_should_stop()) {
 			more_to_do = 1;
 			break;
@@ -1202,13 +1214,13 @@ done:
 }
 
 static int
-do_block_io_op(struct xen_blkif_ring *ring)
+do_block_io_op(struct xen_blkif_ring *ring, unsigned int *eoi_flags)
 {
 	union blkif_back_rings *blk_rings = &ring->blk_rings;
 	int more_to_do;
 
 	do {
-		more_to_do = __do_block_io_op(ring);
+		more_to_do = __do_block_io_op(ring, eoi_flags);
 		if (more_to_do)
 			break;
 
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index b9aa5d1ac10b..5e7c36d73dc6 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -246,9 +246,8 @@ static int xen_blkif_map(struct xen_blkif_ring *ring, grant_ref_t *gref,
 	if (req_prod - rsp_prod > size)
 		goto fail;
 
-	err = bind_interdomain_evtchn_to_irqhandler(blkif->domid, evtchn,
-						    xen_blkif_be_int, 0,
-						    "blkif-backend", ring);
+	err = bind_interdomain_evtchn_to_irqhandler_lateeoi(blkif->domid,
+			evtchn, xen_blkif_be_int, 0, "blkif-backend", ring);
 	if (err < 0)
 		goto fail;
 	ring->irq = err;