Hi Julien,
Julien Grall writes:
Hi Volodymyr,
On 9/11/19 7:48 PM, Volodymyr Babchuk wrote:
Julien Grall writes:
Hi Volodymyr,
On 8/23/19 7:48 PM, Volodymyr Babchuk wrote:
We want to limit number of calls to lookup_and_pin_guest_ram_addr() per one request. There are two ways to do this: either preempt translate_noncontig() or to limit size of one shared buffer size.
It is quite hard to preempt translate_noncontig(), because it is deep nested. So we chose second option. We will allow 512 pages per one shared buffer. This does not interfere with GP standard, as it requires that size limit for shared buffer should be at lest 512kB.
Do you mean "least" instead of "lest"?
Yes
If so, why 512 pages (i.e 1MB) is plenty enough for most of the use cases? What does "xtest" consist on?
Bigger buffer xtest tries to allocate is mere 32KB. I believe that 1MB is enough for the most cases, because OP-TEE itself have a very limited resources. But this value is chosen arbitrary.
Could we potentially reduce to let say 512KB (or maybe lower) if xtest only allocate 32KB?
Potentially - yes. But only to 512KB if we want to be compatible with the Global Platform specification. Why are you asking, though?