From: Aleksandr Partanen <alex.pentagrid@gmail.com>
Date: Thu, 10 Apr 2025 14:46:04 +0000 (+0300)
Subject: xen: mapcache: Fix finding matching entry
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=a4b20f737cda06bb8706a83e27f7fa89863ae689;p=thirdparty%2Fqemu.git

xen: mapcache: Fix finding matching entry

If we have request without lock and hit unlocked or invalid
entry during the search, we remap it immediately,
even if we have matching entry in next entries in bucket.
This leads to duplication of mappings of the same size,
and to possibility of selecting the wrong element
during invalidation and underflow it's entry->lock counter

Signed-off-by: Aleksandr Partanen <alex.pentagrid@gmail.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
---

diff --git a/hw/xen/xen-mapcache.c b/hw/xen/xen-mapcache.c
index 698b5c53ed..2c8f861fdb 100644
--- a/hw/xen/xen-mapcache.c
+++ b/hw/xen/xen-mapcache.c
@@ -376,12 +376,12 @@ tryagain:
 
     entry = &mc->entry[address_index % mc->nr_buckets];
 
-    while (entry && (lock || entry->lock) && entry->vaddr_base &&
-            (entry->paddr_index != address_index || entry->size != cache_size ||
+    while (entry && (!entry->vaddr_base ||
+            entry->paddr_index != address_index || entry->size != cache_size ||
              !test_bits(address_offset >> XC_PAGE_SHIFT,
                  test_bit_size >> XC_PAGE_SHIFT,
                  entry->valid_mapping))) {
-        if (!free_entry && !entry->lock) {
+        if (!free_entry && (!entry->lock || !entry->vaddr_base)) {
             free_entry = entry;
             free_pentry = pentry;
         }