[Qemu-devel] [RFC PATCH qemu] vfio-quirks: Pass the actual parent when deleting a memory region

[Alexey Kardashevskiy]

The usual way of using a quirk's MR is to add it as a subregion of a BAR
as this is what quirks are for. However there is less than standard user
of this - NVLink2-enabled NVIDIA GPU which exposes a GPU RAM and a ATSD
64K region outside of PCI MMIO window so these MRs get the system address
space root as a parent. So when the user unplugs such device, assert
occurs:

qemu-system-ppc64: /home/aik/p/qemu/memory.c:2391: memory_region_del_subregion: 
Assertion `subregion->container == mr' failed.

This passes the actual parent MR to memory_region_del_subregion() in
vfio_bar_quirk_exit.

Signed-off-by: Alexey Kardashevskiy <address@hidden>
---

This removes an extra sanity check that a quirk has a correct parent;
I am not sure if it is very useful.
I could use the "system" MR if quirk->mem[i].container==get_system_memory()
and quirk->mem[i].container otherwise to keep that assert working.

Also this does not help with the actual device removal much because of
the closed source driver nature - the associated service
(nvidia-persistenced, responsible for onlining GPU memory) crashes
the guest system but at least the user can reboot the guest after
the crash which is not as bad as assert.

---
 hw/vfio/pci-quirks.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/hw/vfio/pci-quirks.c b/hw/vfio/pci-quirks.c
index 27dddbc8fa3e..ef2e182c1d36 100644
--- a/hw/vfio/pci-quirks.c
+++ b/hw/vfio/pci-quirks.c
@@ -1896,7 +1896,8 @@ void vfio_bar_quirk_exit(VFIOPCIDevice *vdev, int nr)
         }
 
         for (i = 0; i < quirk->nr_mem; i++) {
-            memory_region_del_subregion(bar->region.mem, &quirk->mem[i]);
+            memory_region_del_subregion(quirk->mem[i].container,
+                                        &quirk->mem[i]);
         }
     }
 }
-- 
2.17.1