On 8/19/2016 11:33 PM, Chris Wilson wrote:
On Fri, Aug 19, 2016 at 02:13:07PM +0530, akash.g...@intel.com wrote:
static void *guc_get_write_buffer(struct intel_guc *guc)
{
- return NULL;
+ /* FIXME: Cover the check under a lock ? */
+ if (!guc->log.relay_chan)
+ return NULL;
+
+ /* Just get the base address of a new sub buffer and copy data into it
+ * ourselves. NULL will be returned in no-overwrite mode, if all sub
+ * buffers are full. Could have used the relay_write() to indirectly
+ * copy the data, but that would have been bit convoluted, as we need to
+ * write to only certain locations inside a sub buffer which cannot be
+ * done without using relay_reserve() along with relay_write(). So its
+ * better to use relay_reserve() alone.
+ */
+ return relay_reserve(guc->log.relay_chan, 0);
}
You have to chase through the code a long way to check whether or not
the allocation is correct.
Please do consider adding a check such as
GEM_BUG_ON(guc->log.relay_chan->size < guc->log.vma->size);
(near the allocation)
Fine, will add a check after the allocation, but not sure how useful it
will be, as we shall trust relay to do the memory allocation for the
sub-buffers as per the requested 'subbuf_size'.
subbuf_size = guc->log.vma->obj->base.size;
n_subbufs = 8;
guc_log_relay_chan = relay_open(NULL, NULL, subbuf_size,
n_subbufs, &relay_callbacks, dev_priv);
GEM_BUG_ON(guc->log.relay_chan->subbuf_size < guc->log.vma->obj->base.size);
GEM_BUG_ON(write_offset + buffer_size > guc->log.relay_chan->size);
(before the memcpy, or whatever is appropriate).
There is a check already for read_offset/write_offset before the memcpy.
I think it would be better to add this check
GEM_BUG_ON(guc->log.relay_chan->subbuf_size < guc->log.vma->obj->base.size);
just before
return relay_reserve(guc->log.relay_chan, 0);
Best regards
Akash
Just to leave some clues to the reader as to what is going on.
-Chris
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