The ioeventfd mechanism is used by vhost, dataplane, and virtio-pci to
turn guest MMIO/PIO writes into eventfd file descriptor events. This
allows arbitrary threads to be notified when the guest writes to a
specific MMIO/PIO address.
qtest and TCG do not support ioeventfd because memory writes are not
checked against registered ioeventfds in QEMU. This patch implements
this in memory_region_dispatch_read() so qtest can use ioeventfd.
This patch is suboptimal because the -machine accel=kvm case now
duplicates ioeventfd matching in QEMU userspace. If kvm.ko didn't match
and we exited to userspace, then matching in QEMU userspace will fail
too.
Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
---
memory.c | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)
Marc-André asked about this patch so I'm sending it now.
This is a first step to making qtest work with vhost. I haven't tested it.
Not sure about irqfd either. Perhaps some work is necessary to make irqfd
work, but I think QEMU already implements that (at least in the virtio-pci
case).
diff --git a/memory.c b/memory.c
index 0acebb1..407fec4 100644
--- a/memory.c
+++ b/memory.c
@@ -1146,6 +1146,32 @@ MemTxResult memory_region_dispatch_read(MemoryRegion *mr,
return r;
}
+/* Return true if an ioeventfd was signalled */
+static bool memory_region_dispatch_write_ioeventfds(MemoryRegion *mr,
+ hwaddr addr,
+ uint64_t data,
+ unsigned size,
+ MemTxAttrs attrs)
+{
+ MemoryRegionIoeventfd ioeventfd = {
+ .addr = addrrange_make(int128_make64(addr), int128_make64(size)),
+ .data = data,
+ };
+ unsigned i;
+
+ for (i = 0; i < mr->ioeventfd_nb; i++) {
+ ioeventfd.match_data = mr->ioeventfds[i].match_data;
+ ioeventfd.e = mr->ioeventfds[i].e;
+
+ if (memory_region_ioeventfd_equal(ioeventfd, mr->ioeventfds[i])) {
+ event_notifier_set(ioeventfd.e);
+ return true;
+ }
+ }
+
+ return false;
+}
+
MemTxResult memory_region_dispatch_write(MemoryRegion *mr,
hwaddr addr,
uint64_t data,
@@ -1159,6 +1185,10 @@ MemTxResult memory_region_dispatch_write(MemoryRegion
*mr,
adjust_endianness(mr, &data, size);
+ if (memory_region_dispatch_write_ioeventfds(mr, addr, data, size, attrs)) {
+ return MEMTX_OK;
+ }
+
if (mr->ops->write) {
return access_with_adjusted_size(addr, &data, size,
mr->ops->impl.min_access_size,
--
2.4.3
