[PATCH V2] xen: Drop out of coroutine context xen_invalidate_map_cache_entry

["Peng Fan (OSS)" <peng.fan@xxxxxxxxxxx>]

From: Peng Fan <peng.fan@xxxxxxx>

xen_invalidate_map_cache_entry is not expected to run in a
coroutine. Without this, there is crash:

    signo=signo@entry=6, no_tid=no_tid@entry=0) at pthread_kill.c:44
    threadid=<optimized out>) at pthread_kill.c:78
    at /usr/src/debug/glibc/2.38+git-r0/sysdeps/posix/raise.c:26
    fmt=0xffff9e1ca8a8 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n",
    assertion=assertion@entry=0xaaaae0d25740 "!qemu_in_coroutine()",
    file=file@entry=0xaaaae0d301a8 "../qemu-xen-dir-remote/block/graph-lock.c", 
line=line@entry=260,
    function=function@entry=0xaaaae0e522c0 <__PRETTY_FUNCTION__.3> 
"bdrv_graph_rdlock_main_loop") at assert.c:92
    assertion=assertion@entry=0xaaaae0d25740 "!qemu_in_coroutine()",
    file=file@entry=0xaaaae0d301a8 "../qemu-xen-dir-remote/block/graph-lock.c", 
line=line@entry=260,
    function=function@entry=0xaaaae0e522c0 <__PRETTY_FUNCTION__.3> 
"bdrv_graph_rdlock_main_loop") at assert.c:101
    at ../qemu-xen-dir-remote/block/graph-lock.c:260
    at 
/home/Freenix/work/sw-stash/xen/upstream/tools/qemu-xen-dir-remote/include/block/graph-lock.h:259
    host=host@entry=0xffff742c8000, size=size@entry=2097152)
    at ../qemu-xen-dir-remote/block/io.c:3362
    host=0xffff742c8000, size=2097152)
    at ../qemu-xen-dir-remote/block/block-backend.c:2859
    host=<optimized out>, size=<optimized out>, max_size=<optimized out>)
    at ../qemu-xen-dir-remote/block/block-ram-registrar.c:33
    size=2097152, max_size=2097152)
    at ../qemu-xen-dir-remote/hw/core/numa.c:883
    buffer=buffer@entry=0xffff743c5000 "")
    at ../qemu-xen-dir-remote/hw/xen/xen-mapcache.c:475
    buffer=buffer@entry=0xffff743c5000 "")
    at ../qemu-xen-dir-remote/hw/xen/xen-mapcache.c:487
    as=as@entry=0xaaaae1ca3ae8 <address_space_memory>, buffer=0xffff743c5000,
    len=<optimized out>, is_write=is_write@entry=true,
    access_len=access_len@entry=32768)
    at ../qemu-xen-dir-remote/system/physmem.c:3199
    dir=DMA_DIRECTION_FROM_DEVICE, len=<optimized out>,
    buffer=<optimized out>, as=0xaaaae1ca3ae8 <address_space_memory>)
    at 
/home/Freenix/work/sw-stash/xen/upstream/tools/qemu-xen-dir-remote/include/sysemu/dma.h:236
    elem=elem@entry=0xaaaaf620aa30, len=len@entry=32769)
    at ../qemu-xen-dir-remote/hw/virtio/virtio.c:758
    elem=elem@entry=0xaaaaf620aa30, len=len@entry=32769, idx=idx@entry=0)
    at ../qemu-xen-dir-remote/hw/virtio/virtio.c:919
    elem=elem@entry=0xaaaaf620aa30, len=32769)
    at ../qemu-xen-dir-remote/hw/virtio/virtio.c:994
    req=req@entry=0xaaaaf620aa30, status=status@entry=0 '\000')
    at ../qemu-xen-dir-remote/hw/block/virtio-blk.c:67
    ret=0) at ../qemu-xen-dir-remote/hw/block/virtio-blk.c:136
    at ../qemu-xen-dir-remote/block/block-backend.c:1559
--Type <RET> for more, q to quit, c to continue without paging--
    at ../qemu-xen-dir-remote/block/block-backend.c:1614
    i1=<optimized out>) at ../qemu-xen-dir-remote/util/coroutine-ucontext.c:177
    at ../sysdeps/unix/sysv/linux/aarch64/setcontext.S:123

Signed-off-by: Peng Fan <peng.fan@xxxxxxx>
---

V2:
 Drop unused ret in XenMapCacheData (thanks Stefano)

 hw/xen/xen-mapcache.c | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/hw/xen/xen-mapcache.c b/hw/xen/xen-mapcache.c
index f7d974677d..8d62b3d2ed 100644
--- a/hw/xen/xen-mapcache.c
+++ b/hw/xen/xen-mapcache.c
@@ -481,11 +481,37 @@ static void 
xen_invalidate_map_cache_entry_unlocked(uint8_t *buffer)
     g_free(entry);
 }
 
-void xen_invalidate_map_cache_entry(uint8_t *buffer)
+typedef struct XenMapCacheData {
+    Coroutine *co;
+    uint8_t *buffer;
+} XenMapCacheData;
+
+static void xen_invalidate_map_cache_entry_bh(void *opaque)
 {
+    XenMapCacheData *data = opaque;
+
     mapcache_lock();
-    xen_invalidate_map_cache_entry_unlocked(buffer);
+    xen_invalidate_map_cache_entry_unlocked(data->buffer);
     mapcache_unlock();
+
+    aio_co_wake(data->co);
+}
+
+void coroutine_mixed_fn xen_invalidate_map_cache_entry(uint8_t *buffer)
+{
+    if (qemu_in_coroutine()) {
+        XenMapCacheData data = {
+            .co = qemu_coroutine_self(),
+            .buffer = buffer,
+        };
+        aio_bh_schedule_oneshot(qemu_get_current_aio_context(),
+                                xen_invalidate_map_cache_entry_bh, &data);
+        qemu_coroutine_yield();
+    } else {
+        mapcache_lock();
+        xen_invalidate_map_cache_entry_unlocked(buffer);
+        mapcache_unlock();
+    }
 }
 
 void xen_invalidate_map_cache(void)
-- 
2.35.3