Akihiko Odaki <akihiko.od...@daynix.com> writes:
> On 2025/06/05 20:57, Alex Bennée wrote:
>> Akihiko Odaki <akihiko.od...@daynix.com> writes:
>>
>>> On 2025/06/03 20:01, Alex Bennée wrote:
>>>> QOM objects can be embedded in other QOM objects and managed as part
>>>> of their lifetime but this isn't the case for
>>>> virtio_gpu_virgl_hostmem_region. However before we can split it out we
>>>> need some other way of associating the wider data structure with the
>>>> memory region.
>>>> Fortunately MemoryRegion has an opaque pointer. This is passed down
>>>> to
>>>> MemoryRegionOps for device type regions but is unused in the
>>>> memory_region_init_ram_ptr() case. Use the opaque to carry the
>>>> reference and allow the final MemoryRegion object to be reaped when
>>>> its reference count is cleared.
>>>> Signed-off-by: Manos Pitsidianakis <manos.pitsidiana...@linaro.org>
>>>> Reviewed-by: Philippe Mathieu-Daudé <phi...@linaro.org>
>>>> Signed-off-by: Alex Bennée <alex.ben...@linaro.org>
>>>> Message-Id: <20250410122643.1747913-2-manos.pitsidiana...@linaro.org>
>>>> Cc: qemu-sta...@nongnu.org
>>>> ---
>>>> include/system/memory.h | 1 +
>>>> hw/display/virtio-gpu-virgl.c | 23 ++++++++---------------
>>>> 2 files changed, 9 insertions(+), 15 deletions(-)
>>>> diff --git a/include/system/memory.h b/include/system/memory.h
>>>> index fc35a0dcad..90715ff44a 100644
>>>> --- a/include/system/memory.h
>>>> +++ b/include/system/memory.h
>>>> @@ -784,6 +784,7 @@ struct MemoryRegion {
>>>> DeviceState *dev;
>>>> const MemoryRegionOps *ops;
>>>> + /* opaque data, used by backends like @ops */
>>>> void *opaque;
>>>> MemoryRegion *container;
>>>> int mapped_via_alias; /* Mapped via an alias, container might be
>>>> NULL */
>>>> diff --git a/hw/display/virtio-gpu-virgl.c b/hw/display/virtio-gpu-virgl.c
>>>> index 145a0b3879..71a7500de9 100644
>>>> --- a/hw/display/virtio-gpu-virgl.c
>>>> +++ b/hw/display/virtio-gpu-virgl.c
>>>> @@ -52,17 +52,11 @@ virgl_get_egl_display(G_GNUC_UNUSED void *cookie)
>>>> #if VIRGL_VERSION_MAJOR >= 1
>>>> struct virtio_gpu_virgl_hostmem_region {
>>>> - MemoryRegion mr;
>>>> + MemoryRegion *mr;
>>>> struct VirtIOGPU *g;
>>>> bool finish_unmapping;
>>>> };
>>>> -static struct virtio_gpu_virgl_hostmem_region *
>>>> -to_hostmem_region(MemoryRegion *mr)
>>>> -{
>>>> - return container_of(mr, struct virtio_gpu_virgl_hostmem_region, mr);
>>>> -}
>>>> -
>>>> static void virtio_gpu_virgl_resume_cmdq_bh(void *opaque)
>>>> {
>>>> VirtIOGPU *g = opaque;
>>>> @@ -73,14 +67,12 @@ static void virtio_gpu_virgl_resume_cmdq_bh(void
>>>> *opaque)
>>>> static void virtio_gpu_virgl_hostmem_region_free(void *obj)
>>>> {
>>>> MemoryRegion *mr = MEMORY_REGION(obj);
>>>> - struct virtio_gpu_virgl_hostmem_region *vmr;
>>>> + struct virtio_gpu_virgl_hostmem_region *vmr = mr->opaque;
>>>> VirtIOGPUBase *b;
>>>> VirtIOGPUGL *gl;
>>>> - vmr = to_hostmem_region(mr);
>>>> - vmr->finish_unmapping = true;
>>>> -
>>>> b = VIRTIO_GPU_BASE(vmr->g);
>>>> + vmr->finish_unmapping = true;
>>>> b->renderer_blocked--;
>>>> /*
>>>> @@ -118,8 +110,8 @@ virtio_gpu_virgl_map_resource_blob(VirtIOGPU *g,
>>>> vmr = g_new0(struct virtio_gpu_virgl_hostmem_region, 1);
>>>> vmr->g = g;
>>>> + mr = g_new0(MemoryRegion, 1);
>>>
>>> This patch does nothing more than adding a separate allocation for
>>> MemoryRegion. Besides there is no corresponding g_free(). This patch
>>> can be simply dropped.
>> As the patch says the MemoryRegion is now free'd when it is
>> de-referenced. Do you have a test case showing it leaking?
>
> "De-referenced" is confusing and sounds like pointer dereferencing.
>
> OBJECT(mr)->free, which has virtio_gpu_virgl_hostmem_region_free() as
> its value, will be called to free mr when the references of mr are
> removed. This patch however does not add a corresponding g_free() call
> to virtio_gpu_virgl_hostmem_region_free(), leaking mr.
>
> AddressSanitizer will catch the memory leak.
Example invocation?
I ran the AddressSantizier against all the virtio-gpu tests yesterday
and it did not complain.
>
> Regards,
> Akihiko Odaki
--
Alex Bennée
Virtualisation Tech Lead @ Linaro
