From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55881) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aMahQ-0000EE-QM for qemu-devel@nongnu.org; Fri, 22 Jan 2016 07:20:21 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aMahL-00017P-QK for qemu-devel@nongnu.org; Fri, 22 Jan 2016 07:20:20 -0500 Received: from mx1.redhat.com ([209.132.183.28]:50502) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aMahL-00017L-Id for qemu-devel@nongnu.org; Fri, 22 Jan 2016 07:20:15 -0500 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) by mx1.redhat.com (Postfix) with ESMTPS id BD0BC38883E for ; Fri, 22 Jan 2016 12:20:14 +0000 (UTC) From: Ladi Prosek Date: Fri, 22 Jan 2016 13:19:58 +0100 Message-Id: <1453465198-11000-1-git-send-email-lprosek@redhat.com> Subject: [Qemu-devel] [PATCH] rng-random: implement request queue List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: amit.shah@redhat.com, Ladi Prosek If the guest adds a buffer to the virtio queue while another buffer is still pending and hasn't been filled and returned by the rng device, rng-random internally discards the pending request, which leads to the second buffer getting stuck in the queue. For the guest this manifests as delayed completion of reads from virtio-rng, i.e. a read is completed only after another read is issued. This patch adds an internal queue of requests, analogous to what rng-egd uses, to make sure that requests and responses are balanced and correctly ordered. Signed-off-by: Ladi Prosek --- backends/rng-random.c | 71 +++++++++++++++++++++++++++++++++++++++------------ 1 file changed, 54 insertions(+), 17 deletions(-) diff --git a/backends/rng-random.c b/backends/rng-random.c index 4e51f46..3f1fd21 100644 --- a/backends/rng-random.c +++ b/backends/rng-random.c @@ -22,10 +22,16 @@ struct RndRandom int fd; char *filename; + GSList *requests; +}; + +typedef struct RngRequest +{ EntropyReceiveFunc *receive_func; void *opaque; size_t size; -}; +} RngRequest; + /** * A simple and incomplete backend to request entropy from /dev/random. @@ -37,19 +43,27 @@ struct RndRandom static void entropy_available(void *opaque) { RndRandom *s = RNG_RANDOM(opaque); - uint8_t buffer[s->size]; - ssize_t len; - len = read(s->fd, buffer, s->size); - if (len < 0 && errno == EAGAIN) { - return; - } - g_assert(len != -1); + while (s->requests != NULL) { + RngRequest *req = s->requests->data; + uint8_t buffer[req->size]; + ssize_t len; + + len = read(s->fd, buffer, req->size); + if (len < 0 && errno == EAGAIN) { + return; + } + g_assert(len != -1); - s->receive_func(s->opaque, buffer, len); - s->receive_func = NULL; + req->receive_func(req->opaque, buffer, len); - qemu_set_fd_handler(s->fd, NULL, NULL, NULL); + s->requests = g_slist_remove_link(s->requests, s->requests); + g_free(req); + } + + if (s->requests == NULL) { + qemu_set_fd_handler(s->fd, NULL, NULL, NULL); + } } static void rng_random_request_entropy(RngBackend *b, size_t size, @@ -57,16 +71,36 @@ static void rng_random_request_entropy(RngBackend *b, size_t size, void *opaque) { RndRandom *s = RNG_RANDOM(b); + RngRequest *req; - if (s->receive_func) { - s->receive_func(s->opaque, NULL, 0); + req = g_malloc(sizeof(*req)); + + req->size = size; + req->receive_func = receive_entropy; + req->opaque = opaque; + + s->requests = g_slist_append(s->requests, req); + if (s->requests->data == req) { + qemu_set_fd_handler(s->fd, entropy_available, NULL, s); + } +} + +static void rng_random_free_requests(RndRandom *s) +{ + GSList *i; + + for (i = s->requests; i; i = i->next) { + g_free(i->data); } - s->receive_func = receive_entropy; - s->opaque = opaque; - s->size = size; + g_slist_free(s->requests); + s->requests = NULL; +} - qemu_set_fd_handler(s->fd, entropy_available, NULL, s); +static void rng_random_cancel_requests(RngBackend *b) +{ + RndRandom *s = RNG_RANDOM(b); + rng_random_free_requests(s); } static void rng_random_opened(RngBackend *b, Error **errp) @@ -129,6 +163,8 @@ static void rng_random_finalize(Object *obj) } g_free(s->filename); + + rng_random_free_requests(s); } static void rng_random_class_init(ObjectClass *klass, void *data) @@ -136,6 +172,7 @@ static void rng_random_class_init(ObjectClass *klass, void *data) RngBackendClass *rbc = RNG_BACKEND_CLASS(klass); rbc->request_entropy = rng_random_request_entropy; + rbc->cancel_requests = rng_random_cancel_requests; rbc->opened = rng_random_opened; } -- 2.5.0