Hi,
On 12.09.18 14:02, Julien Grall wrote:
On 09/11/2018 08:33 PM, Volodymyr Babchuk wrote:
Hi Julien,
Hi,
On 11.09.18 16:37, Julien Grall wrote:
Hi Volodymyr,
On 10/09/18 19:04, Volodymyr Babchuk wrote:
On 10.09.18 17:02, Julien Grall wrote:
On 03/09/18 17:54, Volodymyr Babchuk wrote:
[...]
+ if ( !pages_data_xen_start )
+ return false;
+
+ shm_buf = allocate_shm_buf(ctx, param->u.tmem.shm_ref,
num_pages);
In alocate_shm_buf you are now globally limiting the number of
pages ( (16384) to pin. However, this does not limit per call.
With the current limit, you would could call up to 16384 times
lookup_and_pin_guest_ram_addr(...). On Arm, for p2m related
operation, we limit to 512 iterations in one go before checking the
preemption.
So I think 16384 times is far too much.
So, in other words, I can translate only 2MB buffer (if 4096KB pages
are used), is it right?
2MB for the whole command. So if you have 5 buffer in the command,
then the sum of the buffer should not be bigger than 2MB.
4 buffers, but yes, it can be up to 8MB. Okay, I'll add per-call
counter to limit memory usage for a whole call.
That would need to be reduced to 2MB in total per call. You probably
want to look at max_order(...).
Yes, this is what I was saying. 512 pages per call.
However, 2MB might be too big considering that you also need to
account the SMC call. Does buffer can be passed for fast call?
No, all such calls are yielding calls, so you can ignore time used for
SMC call itself.
How come you can ignore it? It has a cost to trap to EL3.
Strictly speaking, yes. All steps has cost: trap to EL3, dispatch in EL3,
switch to S-EL1, new thread preparation in OP-TEE, context switch in
OP-TEE.
I wanted to tell, that in my opinion, this is negligible in comparison
with the actual call processing. But maybe, I'm wrong there.
--
Volodymyr Babchuk
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