Hello Joao,
On 3/2/23 14:24, Joao Martins wrote:
On 27/02/2023 14:09, Cédric Le Goater wrote:
On 2/22/23 18:49, Avihai Horon wrote:
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -320,6 +320,41 @@ const MemoryRegionOps vfio_region_ops = {
* Device state interfaces
*/
+typedef struct {
+ unsigned long *bitmap;
+ hwaddr size;
+ hwaddr pages;
+} VFIOBitmap;
+
+static VFIOBitmap *vfio_bitmap_alloc(hwaddr size)
+{
+ VFIOBitmap *vbmap = g_try_new0(VFIOBitmap, 1);
I think using g_malloc0() for the VFIOBitmap should be fine. If QEMU can
not allocate a couple of bytes, we are in trouble anyway.
OOM situations are rather unpredictable, and switching to g_malloc0 means we
will exit ungracefully in the middle of fetching dirty bitmaps. And this
function (vfio_bitmap_alloc) overall will be allocating megabytes for terabyte
guests.
It would be ok if we are initializing, but this is at runtime when we do
migration. I think we should stick with g_try_new0. exit on failure should be
reserved to failure to switch the kernel migration state whereby we are likely
to be dealing with a hardware failure and thus requires something more drastic.
I agree for large allocation :
vbmap->bitmap = g_try_malloc0(vbmap->size);
but not for the smaller ones, like VFIOBitmap. You would have to
convert some other g_malloc0() calls, like the one allocating 'unmap'
in vfio_dma_unmap_bitmap(), to be consistent.
Given the size of VFIOBitmap, I think it could live on the stack in
routine vfio_dma_unmap_bitmap() and routine vfio_get_dirty_bitmap()
since the reference is not kept.
The 'vbmap' attribute of vfio_giommu_dirty_notifier does not need
to be a pointer either.
vfio_bitmap_alloc(hwaddr size) could then become
vfio_bitmap_init(VFIOBitmap *vbmap, hwaddr size).
Anyhow, this is minor. It would simplify a bit the exit path
and error handling.
Thanks,
C.
