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

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: 177f9b1ee4 ("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>
This commit is contained in:
David Hildenbrand 2023-10-23 13:13:41 +02:00
parent 69680740ea
commit 364eff6885
1 changed files with 12 additions and 10 deletions
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22
hw/virtio/virtio-mem.c
View File

@ -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();