qemu-devel.nongnu.org archive mirror
 help / color / mirror / Atom feed
* [GIT PULL 0/1] Host Memory Backends and Memory devices queue 2023-11-13
@ 2023-11-13  8:46 David Hildenbrand
  2023-11-13  8:46 ` [GIT PULL 1/1] virtio-mem: fix division by zero in virtio_mem_activate_memslots_to_plug() David Hildenbrand
  2023-11-13 19:26 ` [GIT PULL 0/1] Host Memory Backends and Memory devices queue 2023-11-13 Stefan Hajnoczi
  0 siblings, 2 replies; 3+ messages in thread
From: David Hildenbrand @ 2023-11-13  8:46 UTC (permalink / raw)
  To: qemu-devel; +Cc: David Hildenbrand

The following changes since commit 69680740eafa1838527c90155a7432d51b8ff203:

  Merge tag 'qdev-array-prop' of https://repo.or.cz/qemu/kevin into staging (2023-11-11 11:23:25 +0800)

are available in the Git repository at:

  https://github.com/davidhildenbrand/qemu.git tags/mem-2023-11-13

for you to fetch changes up to 364eff6885a79869a074852d628dfa7a137ba492:

  virtio-mem: fix division by zero in virtio_mem_activate_memslots_to_plug() (2023-11-13 09:35:44 +0100)

----------------------------------------------------------------
Hi,

"Host Memory Backends" and "Memory devices" queue ("mem"):
- One virtio-mem fix leading to a QEMU crash in QEMU debug builds

----------------------------------------------------------------
David Hildenbrand (1):
      virtio-mem: fix division by zero in virtio_mem_activate_memslots_to_plug()

 hw/virtio/virtio-mem.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

-- 
2.41.0



^ permalink raw reply	[flat|nested] 3+ messages in thread

* [GIT PULL 1/1] virtio-mem: fix division by zero in virtio_mem_activate_memslots_to_plug()
  2023-11-13  8:46 [GIT PULL 0/1] Host Memory Backends and Memory devices queue 2023-11-13 David Hildenbrand
@ 2023-11-13  8:46 ` David Hildenbrand
  2023-11-13 19:26 ` [GIT PULL 0/1] Host Memory Backends and Memory devices queue 2023-11-13 Stefan Hajnoczi
  1 sibling, 0 replies; 3+ messages in thread
From: David Hildenbrand @ 2023-11-13  8:46 UTC (permalink / raw)
  To: qemu-devel
  Cc: David Hildenbrand, Mario Casquero, Michael S . Tsirkin,
	Maciej S . Szmigiero

When running with "dynamic-memslots=off", we enter
virtio_mem_activate_memslots_to_plug() to return immediately again
because "vmem->dynamic_memslots == false". However, the compiler might
not optimize out calculating start_idx+end_idx, where we divide by
vmem->memslot_size. In such a configuration, the memslot size is 0 and
we'll get a division by zero:

    (qemu) qom-set vmem0 requested-size 3G
    (qemu) q35.sh: line 38: 622940 Floating point exception(core dumped)

The same is true for virtio_mem_deactivate_unplugged_memslots(), however
we never really reach that code without a prior
virtio_mem_activate_memslots_to_plug() call.

Let's fix it by simply calling these functions only with
"dynamic-memslots=on".

This was found when using a debug build of QEMU.

Message-ID: <20231023111341.219317-1-david@redhat.com>
Reprted-by: Mario Casquero <mcasquer@redhat.com>
Fixes: 177f9b1ee464 ("virtio-mem: Expose device memory dynamically via multiple memslots if enabled")
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Tested-by: Mario Casquero <mcasquer@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 hw/virtio/virtio-mem.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c
index a5ea3be414..75ee38aa46 100644
--- a/hw/virtio/virtio-mem.c
+++ b/hw/virtio/virtio-mem.c
@@ -525,9 +525,7 @@ static void virtio_mem_activate_memslots_to_plug(VirtIOMEM *vmem,
                                  vmem->memslot_size;
     unsigned int idx;
 
-    if (!vmem->dynamic_memslots) {
-        return;
-    }
+    assert(vmem->dynamic_memslots);
 
     /* Activate all involved memslots in a single transaction. */
     memory_region_transaction_begin();
@@ -547,9 +545,7 @@ static void virtio_mem_deactivate_unplugged_memslots(VirtIOMEM *vmem,
                                  vmem->memslot_size;
     unsigned int idx;
 
-    if (!vmem->dynamic_memslots) {
-        return;
-    }
+    assert(vmem->dynamic_memslots);
 
     /* Deactivate all memslots with unplugged blocks in a single transaction. */
     memory_region_transaction_begin();
@@ -598,7 +594,9 @@ static int virtio_mem_set_block_state(VirtIOMEM *vmem, uint64_t start_gpa,
         virtio_mem_notify_unplug(vmem, offset, size);
         virtio_mem_set_range_unplugged(vmem, start_gpa, size);
         /* Deactivate completely unplugged memslots after updating the state. */
-        virtio_mem_deactivate_unplugged_memslots(vmem, offset, size);
+        if (vmem->dynamic_memslots) {
+            virtio_mem_deactivate_unplugged_memslots(vmem, offset, size);
+        }
         return 0;
     }
 
@@ -635,9 +633,11 @@ static int virtio_mem_set_block_state(VirtIOMEM *vmem, uint64_t start_gpa,
          * blocks we are plugging here. The following notification will inform
          * registered listeners about the blocks we're plugging.
          */
-        virtio_mem_activate_memslots_to_plug(vmem, offset, size);
+        if (vmem->dynamic_memslots) {
+            virtio_mem_activate_memslots_to_plug(vmem, offset, size);
+        }
         ret = virtio_mem_notify_plug(vmem, offset, size);
-        if (ret) {
+        if (ret && vmem->dynamic_memslots) {
             virtio_mem_deactivate_unplugged_memslots(vmem, offset, size);
         }
     }
@@ -749,7 +749,9 @@ static int virtio_mem_unplug_all(VirtIOMEM *vmem)
         notifier_list_notify(&vmem->size_change_notifiers, &vmem->size);
 
         /* Deactivate all memslots after updating the state. */
-        virtio_mem_deactivate_unplugged_memslots(vmem, 0, region_size);
+        if (vmem->dynamic_memslots) {
+            virtio_mem_deactivate_unplugged_memslots(vmem, 0, region_size);
+        }
     }
 
     trace_virtio_mem_unplugged_all();
-- 
2.41.0



^ permalink raw reply related	[flat|nested] 3+ messages in thread

* Re: [GIT PULL 0/1] Host Memory Backends and Memory devices queue 2023-11-13
  2023-11-13  8:46 [GIT PULL 0/1] Host Memory Backends and Memory devices queue 2023-11-13 David Hildenbrand
  2023-11-13  8:46 ` [GIT PULL 1/1] virtio-mem: fix division by zero in virtio_mem_activate_memslots_to_plug() David Hildenbrand
@ 2023-11-13 19:26 ` Stefan Hajnoczi
  1 sibling, 0 replies; 3+ messages in thread
From: Stefan Hajnoczi @ 2023-11-13 19:26 UTC (permalink / raw)
  To: David Hildenbrand; +Cc: qemu-devel, David Hildenbrand

[-- Attachment #1: Type: text/plain, Size: 115 bytes --]

Applied, thanks.

Please update the changelog at https://wiki.qemu.org/ChangeLog/8.2 for any user-visible changes.

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2023-11-13 19:29 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2023-11-13  8:46 [GIT PULL 0/1] Host Memory Backends and Memory devices queue 2023-11-13 David Hildenbrand
2023-11-13  8:46 ` [GIT PULL 1/1] virtio-mem: fix division by zero in virtio_mem_activate_memslots_to_plug() David Hildenbrand
2023-11-13 19:26 ` [GIT PULL 0/1] Host Memory Backends and Memory devices queue 2023-11-13 Stefan Hajnoczi

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).