Re: [qemu] boot failed: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000

On 06-07-20, 07:33, Dave Jiang wrote:

...

I don't see anything suspicious in dmaengine drivers, but there is a recent series from Dave Jiang that might explain it. Could you try reverting commit deb9541f5052 ("dmaengine: check device and channel list for empty")?

I think the broken change is this one:

@@ -819,6 +850,11 @@ struct dma_chan *dma_request_chan(struct device *dev, const char *name)

     /* Try to find the channel via the DMA filter map(s) */
     mutex_lock(&dma_list_mutex);

•   if (list_empty(&dma_device_list)) {
  

•           mutex_unlock(&dma_list_mutex);
  

•           return NULL;
  

•   }
  

•    list_for_each_entry_safe(d, _d, &dma_device_list, global_node) {
             dma_cap_mask_t mask;
             const struct dma_slave_map *map = dma_filter_match(d,
  

name, dev);

which needs to return an error code like -ENODEV instead of NULL. There may be other changes in the same patch that introduce the same bug elsewhere.

  Arnd

Vinod, Do you want a diff fix or a revision of the patch for the fix?

Diff fix please