Re: [PATCH RFC 2/7] virtio-gpu-virgl: check page alignment of blob mapping

[Akihiko Odaki]

On 2025/12/03 13:07, Joelle van Dyne wrote:
Currently if a mapping is not page aligned, it will sliently fail and the
guest, assuming it is mapped, will attempt to access the memory and fail.
This is particularly an issue on macOS when the host page size is 16KiB and
the guest page size is 4KiB.

It should work. If I understand correctly, tcg doesn't care the host 
page size. hvf will not call hv_vm_map() for misaligned regions and that 
causes Data Abort, but it is handled by QEMU to perform memory access. I 
think it needs more debugging.

Regards,
Akihiko Odaki


Signed-off-by: Joelle van Dyne <j...@getutm.app>
---
  hw/display/virtio-gpu-virgl.c | 14 ++++++++++++++
  1 file changed, 14 insertions(+)

diff --git a/hw/display/virtio-gpu-virgl.c b/hw/display/virtio-gpu-virgl.c
index 20c856c04e..adf02ac22b 100644
--- a/hw/display/virtio-gpu-virgl.c
+++ b/hw/display/virtio-gpu-virgl.c
@@ -116,6 +116,20 @@ virtio_gpu_virgl_map_resource_blob(VirtIOGPU *g,
          return ret;
      }
  
+    if (!QEMU_IS_ALIGNED((uintptr_t)data, qemu_real_host_page_size())) {
+        virgl_renderer_resource_unmap(res->base.resource_id);
+        qemu_log_mask(LOG_GUEST_ERROR, "%s: address %p is not aligned to page 
size\n",
+                      __func__, data);
+        return -ENOMEM;
+    }
+
+    if (!QEMU_IS_ALIGNED(size, qemu_real_host_page_size())) {
+        virgl_renderer_resource_unmap(res->base.resource_id);
+        qemu_log_mask(LOG_GUEST_ERROR, "%s: size 0x%llx is not aligned to page 
size\n",
+                      __func__, size);
+        return -ENOMEM;
+    }
+
      vmr = g_new0(struct virtio_gpu_virgl_hostmem_region, 1);
      vmr->g = g;