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[Stable-8.1.3 34/55] hw/xen: fix XenStore watch delivery to guest
From: |
Michael Tokarev |
Subject: |
[Stable-8.1.3 34/55] hw/xen: fix XenStore watch delivery to guest |
Date: |
Thu, 9 Nov 2023 16:42:38 +0300 |
From: David Woodhouse <dwmw@amazon.co.uk>
When fire_watch_cb() found the response buffer empty, it would call
deliver_watch() to generate the XS_WATCH_EVENT message in the response
buffer and send an event channel notification to the guest… without
actually *copying* the response buffer into the ring. So there was
nothing for the guest to see. The pending response didn't actually get
processed into the ring until the guest next triggered some activity
from its side.
Add the missing call to put_rsp().
It might have been slightly nicer to call xen_xenstore_event() here,
which would *almost* have worked. Except for the fact that it calls
xen_be_evtchn_pending() to check that it really does have an event
pending (and clear the eventfd for next time). And under Xen it's
defined that setting that fd to O_NONBLOCK isn't guaranteed to work,
so the emu implementation follows suit.
This fixes Xen device hot-unplug.
Cc: qemu-stable@nongnu.org
Fixes: 0254c4d19df ("hw/xen: Add xenstore wire implementation and
implementation stubs")
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
(cherry picked from commit 4a5780f52095f1daf23618dc6198a2a1665ea505)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
diff --git a/hw/i386/kvm/xen_xenstore.c b/hw/i386/kvm/xen_xenstore.c
index 133d89e953..725ca2f15d 100644
--- a/hw/i386/kvm/xen_xenstore.c
+++ b/hw/i386/kvm/xen_xenstore.c
@@ -1357,10 +1357,12 @@ static void fire_watch_cb(void *opaque, const char
*path, const char *token)
} else {
deliver_watch(s, path, token);
/*
- * If the message was queued because there was already ring activity,
- * no need to wake the guest. But if not, we need to send the evtchn.
+ * Attempt to queue the message into the actual ring, and send
+ * the event channel notification if any bytes are copied.
*/
- xen_be_evtchn_notify(s->eh, s->be_port);
+ if (s->rsp_pending && put_rsp(s) > 0) {
+ xen_be_evtchn_notify(s->eh, s->be_port);
+ }
}
}
--
2.39.2
- [Stable-8.1.3 24/55] qemu-iotests: 024: add rebasing test case for overlay_size > backing_size, (continued)
- [Stable-8.1.3 24/55] qemu-iotests: 024: add rebasing test case for overlay_size > backing_size, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 26/55] target/arm: Correctly propagate stage 1 BTI guarded bit in a two-stage walk, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 28/55] vfio/pci: Fix buffer overrun when writing the VF token, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 27/55] util/uuid: Add UUID_STR_LEN definition, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 29/55] util/uuid: Remove UUID_FMT_LEN, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 30/55] i386/xen: Don't advertise XENFEAT_supervisor_mode_kernel, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 35/55] hw/xen: take iothread mutex in xen_evtchn_reset_op(), Michael Tokarev, 2023/11/09
- [Stable-8.1.3 32/55] hw/xen: select kernel mode for per-vCPU event channel upcall vector, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 31/55] i386/xen: fix per-vCPU upcall vector for Xen emulation, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 33/55] hw/xen: don't clear map_track[] in xen_gnttab_reset(), Michael Tokarev, 2023/11/09
- [Stable-8.1.3 34/55] hw/xen: fix XenStore watch delivery to guest,
Michael Tokarev <=
- [Stable-8.1.3 39/55] target/arm: Fix A64 LDRA immediate decode, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 36/55] hw/xen: use correct default protocol for xen-block on x86, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 37/55] virtio-gpu: block migration of VMs with blob=true, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 38/55] block/nvme: nvme_process_completion() fix bound for cid, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 41/55] block/file-posix: fix update_zones_wp() caller, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 45/55] ui/gtk-egl: apply scale factor when calculating window's dimension, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 40/55] qcow2: keep reference on zeroize with discard-no-unref enabled, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 42/55] file-posix: fix over-writing of returning zone_append offset, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 43/55] ati-vga: Implement fallback for pixman routines, Michael Tokarev, 2023/11/09
- [Stable-8.1.3 44/55] ui/gtk: force realization of drawing area, Michael Tokarev, 2023/11/09