From c70b7741dda7586529cc270e0f2c4cae3921b9b1 Mon Sep 17 00:00:00 2001 From: Volodymyr Babchuk Date: Thu, 19 Jan 2023 21:11:15 +0000 Subject: [PATCH] xen/pvcalls-back: fix permanently masked event channel There is a sequence of events that can lead to a permanently masked event channel, because xen_irq_lateeoi() is newer called. This happens when a backend receives spurious write event from a frontend. In this case pvcalls_conn_back_write() returns early and it does not clears the map->write counter. As map->write > 0, pvcalls_back_ioworker() returns without calling xen_irq_lateeoi(). This leaves the event channel in masked state, a backend does not receive any new events from a frontend and the whole communication stops. Move atomic_set(&map->write, 0) to the very beginning of pvcalls_conn_back_write() to fix this issue. Signed-off-by: Volodymyr Babchuk Reported-by: Oleksii Moisieiev Reviewed-by: Juergen Gross Link: https://lore.kernel.org/r/20230119211037.1234931-1-volodymyr_babchuk@epam.com Signed-off-by: Juergen Gross --- drivers/xen/pvcalls-back.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c index 0d4f8f4f4948..7a464a541d91 100644 --- a/drivers/xen/pvcalls-back.c +++ b/drivers/xen/pvcalls-back.c @@ -173,6 +173,8 @@ static bool pvcalls_conn_back_write(struct sock_mapping *map) RING_IDX cons, prod, size, array_size; int ret; + atomic_set(&map->write, 0); + cons = intf->out_cons; prod = intf->out_prod; /* read the indexes before dealing with the data */ @@ -197,7 +199,6 @@ static bool pvcalls_conn_back_write(struct sock_mapping *map) iov_iter_kvec(&msg.msg_iter, ITER_SOURCE, vec, 2, size); } - atomic_set(&map->write, 0); ret = inet_sendmsg(map->sock, &msg, size); if (ret == -EAGAIN) { atomic_inc(&map->write);