On 16/06/2015 21:25, Chris Wilson wrote:
On Tue, Jun 16, 2015 at 08:25:20PM +0100, Arun Siluvery wrote:
+static int gen8_init_indirectctx_bb(struct intel_engine_cs *ring,
+ uint32_t offset,
+ uint32_t *num_dwords)
+{
+ uint32_t index;
+ struct page *page;
+ uint32_t *cmd;
+
+ page = i915_gem_object_get_page(ring->wa_ctx.obj, 0);
+ cmd = kmap_atomic(page);
+
+ index = offset;
+
+ /* FIXME: fill one cacheline with NOOPs.
+ * Replace these instructions with WA
+ */
+ while (index < (offset + 16))
+ cmd[index++] = MI_NOOP;
+
+ /*
+ * MI_BATCH_BUFFER_END is not required in Indirect ctx BB because
+ * execution depends on the length specified in terms of cache lines
+ * in the register CTX_RCS_INDIRECT_CTX
+ */
+
+ kunmap_atomic(cmd);
+
+ if (index > (PAGE_SIZE / sizeof(uint32_t)))
+ return -EINVAL;
Check before you GPF!
You just overran the buffer and corrupted memory, if you didn't succeed
in trapping a segfault.
To be generic, align to the cacheline then check you have enough room
for your own data.
-Chris
Hi Chris,
The placement of condition is not correct. I don't completely follow
your suggestion, could you please elaborate; here we don't know upfront
how much more data to be written.
I have made below changes to check after writing every command and
return error as soon as we reach the end.
#define wa_ctx_emit(batch, cmd) { \
if (WARN_ON(index >= (PAGE_SIZE / sizeof(uint32_t)))) { \
kunmap_atomic(batch); \
return -ENOSPC; \
} \
batch[index++] = (cmd); \
}
is this acceptable?
I think this is the only one issue, all other comments are addressed.
regards
Arun
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