qemu-kvm/kvm-vfio-common-return-early-if-space-isn-t-empty.patch

From e9476ee64edd81fafd409fb3ceaad80668446bff Mon Sep 17 00:00:00 2001
From: Zhenzhong Duan <zhenzhong.duan@intel.com>
Date: Tue, 21 Nov 2023 16:44:02 +0800
Subject: [PATCH 023/101] vfio/common: return early if space isn't empty
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RH-Author: Eric Auger <eric.auger@redhat.com>
RH-MergeRequest: 211: IOMMUFD backend backport
RH-Jira: RHEL-19302 RHEL-21057
RH-Acked-by: Cédric Le Goater <clg@redhat.com>
RH-Acked-by: Sebastian Ott <sebott@redhat.com>
RH-Commit: [22/67] 239c21ae7cddc8efabc041b9c7774f15b4964631 (eauger1/centos-qemu-kvm)

This is a trivial optimization. If there is active container in space,
vfio_reset_handler will never be unregistered. So revert the check of
space->containers and return early.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
(cherry picked from commit 1eae5b7bd3ddd03b5591e9122b011c6520064a5a)
Signed-off-by: Eric Auger <eric.auger@redhat.com>
---
 hw/vfio/common.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 572ae7c934..934f4f5446 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -1462,10 +1462,13 @@ VFIOAddressSpace *vfio_get_address_space(AddressSpace *as)
 
 void vfio_put_address_space(VFIOAddressSpace *space)
 {
-    if (QLIST_EMPTY(&space->containers)) {
-        QLIST_REMOVE(space, list);
-        g_free(space);
+    if (!QLIST_EMPTY(&space->containers)) {
+        return;
     }
+
+    QLIST_REMOVE(space, list);
+    g_free(space);
+
     if (QLIST_EMPTY(&vfio_address_spaces)) {
         qemu_unregister_reset(vfio_reset_handler, NULL);
     }
-- 
2.39.3