linux-kernel - Re: [PATCH v9 00/13] firmware: qcom: qseecom: convert to using the TZ allocator

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Date: Fri, 29 Mar 2024 19:56:13 +0100
From: Maximilian Luz <luzmaximilian@...il.com>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Andy Gross <agross@...nel.org>, Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konrad.dybcio@...aro.org>,
 Elliot Berman <quic_eberman@...cinc.com>,
 Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
 Guru Das Srinagesh <quic_gurus@...cinc.com>,
 Andrew Halaney <ahalaney@...hat.com>, Alex Elder <elder@...aro.org>,
 Srini Kandagatla <srinivas.kandagatla@...aro.org>,
 Arnd Bergmann <arnd@...db.de>, linux-arm-msm@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 kernel@...cinc.com, Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v9 00/13] firmware: qcom: qseecom: convert to using the TZ
 allocator



On 3/29/24 7:53 PM, Maximilian Luz wrote:
> On 3/29/24 11:22 AM, Bartosz Golaszewski wrote:
>> On Thu, Mar 28, 2024 at 7:55 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:
>>>
>>> On Thu, Mar 28, 2024 at 5:50 PM Maximilian Luz <luzmaximilian@...il.com> wrote:
>>>>
>>>> If I understand correctly, it enters an atomic section in
>>>> qcom_tzmem_alloc() and then tries to schedule somewhere down the line.
>>>> So this shouldn't be qseecom specific.
>>>>
>>>> I should probably also say that I'm currently testing this on a patched
>>>> v6.8 kernel, so there's a chance that it's my fault. However, as far as
>>>> I understand, it enters an atomic section in qcom_tzmem_alloc() and then
>>>> later tries to expand the pool memory with dma_alloc_coherent(). Which
>>>> AFAIK is allowed to sleep with GFP_KERNEL (and I guess that that's the
>>>> issue here).
>>>>
>>>> I've also tried the shmem allocator option, but that seems to get stuck
>>>> quite early at boot, before I even have usb-serial access to get any
>>>> logs. If I can find some more time, I'll try to see if I can get some
>>>> useful output for that.
>>>>
>>>
>>> Ah, I think it happens here:
>>>
>>> +       guard(spinlock_irqsave)(&pool->lock);
>>> +
>>> +again:
>>> +       vaddr = gen_pool_alloc(pool->genpool, size);
>>> +       if (!vaddr) {
>>> +               if (qcom_tzmem_try_grow_pool(pool, size, gfp))
>>> +                       goto again;
>>>
>>> We were called with GFP_KERNEL so this is what we pass on to
>>> qcom_tzmem_try_grow_pool() but we're now holding the spinlock. I need
>>> to revisit it. Thanks for the catch!
>>>
>>> Bart
>>
>> Can you try the following tree?
>>
>>      https://git.codelinaro.org/bartosz_golaszewski/linux.git
>> topic/shm-bridge-v10
>>
>> gen_pool_alloc() and gen_pool_add_virt() can be used without external
>> serialization. We only really need to protect the list of areas in the
>> pool when adding a new element. We could possibly even use
>> list_add_tail_rcu() as it updates the pointers atomically and go
>> lockless.
> 
> Thanks! That fixes the allocations for CONFIG_QCOM_TZMEM_MODE_GENERIC=y.
> Unfortunately, with the shmbridge mode it still gets stuck at boot (and
> I haven't had the time to look into it yet).
> 
> And for more bad news: It looks like the new allocator now fully exposes
> a bug that I've been tracking down the last couple of days. In short,
> uefisecapp doesn't seem to be happy when we split the allocations for
> request and response into two, causing commands to fail. Instead it
> wants a single buffer for both. Before, it seemed to be fairly sporadic
> (likely because kzalloc in sequence just returned consecutive memory
> almost all of the time) but now it's basically every call that fails.
> 
> I have a fix for that almost ready and I'll likely post it in the next
> hour. But that means that you'll probably have to rebase this series
> on top of it...

Forgot to mention: I tested it with the fix and this series, and that
works.

> Best regards,
> Max
>