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From: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
To: Julien Grall <julien.grall@arm.com>
Cc: "tee-dev@lists.linaro.org" <tee-dev@lists.linaro.org>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
Subject: Re: [Xen-devel] [PATCH 1/5] xen/arm: optee: impose limit on shared buffer size
Date: Thu, 12 Sep 2019 19:45:37 +0000	[thread overview]
Message-ID: <87h85hfgda.fsf@epam.com> (raw)
In-Reply-To: <1cc4bd9c-44fc-0e6e-254c-c07f4b17ba4c@arm.com>


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?


-- 
Volodymyr Babchuk at EPAM
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  reply	other threads:[~2019-09-12 19:46 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-23 18:48 [Xen-devel] [PATCH 0/5] arch/arm: optee: fix TODOs and remove "experimental" status Volodymyr Babchuk
2019-08-23 18:48 ` [Xen-devel] [PATCH 1/5] xen/arm: optee: impose limit on shared buffer size Volodymyr Babchuk
2019-09-09 22:11   ` Julien Grall
2019-09-11 18:48     ` Volodymyr Babchuk
2019-09-12 19:32       ` Julien Grall
2019-09-12 19:45         ` Volodymyr Babchuk [this message]
2019-09-12 19:51           ` Julien Grall
2019-09-16 15:26             ` Volodymyr Babchuk
2019-09-17 10:49               ` Julien Grall
2019-09-17 12:28                 ` Volodymyr Babchuk
2019-09-17 18:46                   ` Julien Grall
2019-08-23 18:48 ` [Xen-devel] [PATCH 2/5] xen/arm: optee: check for preemption while freeing shared buffers Volodymyr Babchuk
2019-09-09 22:19   ` Julien Grall
2019-09-11 18:53     ` Volodymyr Babchuk
2019-09-12 19:39       ` Julien Grall
2019-09-12 19:47         ` Volodymyr Babchuk
2019-08-23 18:48 ` [Xen-devel] [PATCH 3/5] xen/arm: optee: limit number of " Volodymyr Babchuk
2019-08-23 18:48 ` [Xen-devel] [PATCH 4/5] xen/arm: optee: handle share buffer translation error Volodymyr Babchuk
2019-09-10 11:17   ` Julien Grall
2019-09-11 18:32     ` Volodymyr Babchuk
2019-09-12 18:55       ` Julien Grall
2019-08-23 18:48 ` [Xen-devel] [PATCH 5/5] xen/arm: optee: remove experimental status Volodymyr Babchuk
2019-08-23 19:05   ` Julien Grall
2019-08-23 19:20     ` Volodymyr Babchuk
2019-09-09 21:31       ` Julien Grall
2019-09-11 18:41         ` Volodymyr Babchuk
2019-09-12 19:00           ` Julien Grall

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