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[Qemu-devel] [PULL 29/40] ivshmem: Simplify how we cope with short reads
From: |
Markus Armbruster |
Subject: |
[Qemu-devel] [PULL 29/40] ivshmem: Simplify how we cope with short reads from server |
Date: |
Fri, 18 Mar 2016 18:01:16 +0100 |
Short reads from a UNIX domain sockets are exceedingly unlikely when
the other side always sends eight bytes and we always read eight
bytes. We cope with them anyway. However, the code doing that is
rather convoluted. Dumb it down radically.
Signed-off-by: Markus Armbruster <address@hidden>
Reviewed-by: Marc-André Lureau <address@hidden>
Message-Id: <address@hidden>
---
hw/misc/ivshmem.c | 75 ++++++++++++-------------------------------------------
1 file changed, 16 insertions(+), 59 deletions(-)
diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
index c1a75db..7b9e769 100644
--- a/hw/misc/ivshmem.c
+++ b/hw/misc/ivshmem.c
@@ -26,7 +26,6 @@
#include "migration/migration.h"
#include "qemu/error-report.h"
#include "qemu/event_notifier.h"
-#include "qemu/fifo8.h"
#include "sysemu/char.h"
#include "sysemu/hostmem.h"
#include "qapi/visitor.h"
@@ -80,7 +79,6 @@ typedef struct IVShmemState {
uint32_t intrstatus;
CharDriverState *server_chr;
- Fifo8 incoming_fifo;
MemoryRegion ivshmem_mmio;
/* We might need to register the BAR before we actually have the memory.
@@ -99,6 +97,8 @@ typedef struct IVShmemState {
uint32_t vectors;
uint32_t features;
MSIVector *msi_vectors;
+ uint64_t msg_buf; /* buffer for receiving server messages */
+ int msg_buffered_bytes; /* #bytes in @msg_buf */
Error *migration_blocker;
@@ -255,11 +255,6 @@ static const MemoryRegionOps ivshmem_mmio_ops = {
},
};
-static int ivshmem_can_receive(void * opaque)
-{
- return sizeof(int64_t);
-}
-
static void ivshmem_vector_notify(void *opaque)
{
MSIVector *entry = opaque;
@@ -459,53 +454,6 @@ static void resize_peers(IVShmemState *s, int nb_peers)
}
}
-static bool fifo_update_and_get(IVShmemState *s, const uint8_t *buf, int size,
- void *data, size_t len)
-{
- const uint8_t *p;
- uint32_t num;
-
- assert(len <= sizeof(int64_t)); /* limitation of the fifo */
- if (fifo8_is_empty(&s->incoming_fifo) && size == len) {
- memcpy(data, buf, size);
- return true;
- }
-
- IVSHMEM_DPRINTF("short read of %d bytes\n", size);
-
- num = MIN(size, sizeof(int64_t) - fifo8_num_used(&s->incoming_fifo));
- fifo8_push_all(&s->incoming_fifo, buf, num);
-
- if (fifo8_num_used(&s->incoming_fifo) < len) {
- assert(num == 0);
- return false;
- }
-
- size -= num;
- buf += num;
- p = fifo8_pop_buf(&s->incoming_fifo, len, &num);
- assert(num == len);
-
- memcpy(data, p, len);
-
- if (size > 0) {
- fifo8_push_all(&s->incoming_fifo, buf, size);
- }
-
- return true;
-}
-
-static bool fifo_update_and_get_i64(IVShmemState *s,
- const uint8_t *buf, int size, int64_t *i64)
-{
- if (fifo_update_and_get(s, buf, size, i64, sizeof(*i64))) {
- *i64 = GINT64_FROM_LE(*i64);
- return true;
- }
-
- return false;
-}
-
static void ivshmem_add_kvm_msi_virq(IVShmemState *s, int vector,
Error **errp)
{
@@ -658,6 +606,14 @@ static void process_msg(IVShmemState *s, int64_t msg, int
fd, Error **errp)
}
}
+static int ivshmem_can_receive(void *opaque)
+{
+ IVShmemState *s = opaque;
+
+ assert(s->msg_buffered_bytes < sizeof(s->msg_buf));
+ return sizeof(s->msg_buf) - s->msg_buffered_bytes;
+}
+
static void ivshmem_read(void *opaque, const uint8_t *buf, int size)
{
IVShmemState *s = opaque;
@@ -665,9 +621,14 @@ static void ivshmem_read(void *opaque, const uint8_t *buf,
int size)
int fd;
int64_t msg;
- if (!fifo_update_and_get_i64(s, buf, size, &msg)) {
+ assert(size >= 0 && s->msg_buffered_bytes + size <= sizeof(s->msg_buf));
+ memcpy((unsigned char *)&s->msg_buf + s->msg_buffered_bytes, buf, size);
+ s->msg_buffered_bytes += size;
+ if (s->msg_buffered_bytes < sizeof(s->msg_buf)) {
return;
}
+ msg = le64_to_cpu(s->msg_buf);
+ s->msg_buffered_bytes = 0;
fd = qemu_chr_fe_get_msgfd(s->server_chr);
IVSHMEM_DPRINTF("posn is %" PRId64 ", fd is %d\n", msg, fd);
@@ -1022,8 +983,6 @@ static void pci_ivshmem_realize(PCIDevice *dev, Error
**errp)
}
}
- fifo8_create(&s->incoming_fifo, sizeof(int64_t));
-
if (s->role_val == IVSHMEM_PEER) {
error_setg(&s->migration_blocker,
"Migration is disabled when using feature 'peer mode' in
device 'ivshmem'");
@@ -1036,8 +995,6 @@ static void pci_ivshmem_exit(PCIDevice *dev)
IVShmemState *s = IVSHMEM(dev);
int i;
- fifo8_destroy(&s->incoming_fifo);
-
if (s->migration_blocker) {
migrate_del_blocker(s->migration_blocker);
error_free(s->migration_blocker);
--
2.4.3
- [Qemu-devel] [PULL 14/40] ivshmem: Drop ivshmem_event() stub, (continued)
- [Qemu-devel] [PULL 14/40] ivshmem: Drop ivshmem_event() stub, Markus Armbruster, 2016/03/18
- [Qemu-devel] [PULL 24/40] ivshmem: Plug leaks on unplug, fix peer disconnect, Markus Armbruster, 2016/03/18
- [Qemu-devel] [PULL 38/40] ivshmem: Drop ivshmem property x-memdev, Markus Armbruster, 2016/03/18
- [Qemu-devel] [PULL 20/40] ivshmem: Leave INTx alone when using MSI-X, Markus Armbruster, 2016/03/18
- [Qemu-devel] [PULL 39/40] ivshmem: Require master to have ID zero, Markus Armbruster, 2016/03/18
- [Qemu-devel] [PULL 33/40] ivshmem: Inline check_shm_size() into its only caller, Markus Armbruster, 2016/03/18
- [Qemu-devel] [PULL 26/40] ivshmem: Propagate errors through ivshmem_recv_setup(), Markus Armbruster, 2016/03/18
- [Qemu-devel] [PULL 10/40] ivshmem: Rewrite specification document, Markus Armbruster, 2016/03/18
- [Qemu-devel] [PULL 32/40] ivshmem: Simplify memory regions for BAR 2 (shared memory), Markus Armbruster, 2016/03/18
- [Qemu-devel] [PULL 04/40] qemu-doc: Fix ivshmem huge page example, Markus Armbruster, 2016/03/18
- [Qemu-devel] [PULL 29/40] ivshmem: Simplify how we cope with short reads from server,
Markus Armbruster <=
- [Qemu-devel] [PULL 19/40] ivshmem: Clean up MSI-X conditions, Markus Armbruster, 2016/03/18
- [Qemu-devel] [PULL 35/40] ivshmem: Replace int role_val by OnOffAuto master, Markus Armbruster, 2016/03/18
- [Qemu-devel] [PULL 13/40] ivshmem: Clean up after commit 9940c32, Markus Armbruster, 2016/03/18
- [Qemu-devel] [PULL 02/40] ivshmem-server: Fix and clean up command line help, Markus Armbruster, 2016/03/18
- [Qemu-devel] [PULL 23/40] ivshmem: Disentangle ivshmem_read(), Markus Armbruster, 2016/03/18
- [Qemu-devel] [PULL 16/40] ivshmem: Fix harmless misuse of Error, Markus Armbruster, 2016/03/18
- [Qemu-devel] [PULL 17/40] ivshmem: Failed realize() can leave migration blocker behind, Markus Armbruster, 2016/03/18
- [Qemu-devel] [PULL 25/40] ivshmem: Receive shared memory synchronously in realize(), Markus Armbruster, 2016/03/18
- [Qemu-devel] [PULL 30/40] ivshmem: Tighten check of property "size", Markus Armbruster, 2016/03/18
- [Qemu-devel] [PULL 27/40] ivshmem: Rely on server sending the ID right after the version, Markus Armbruster, 2016/03/18