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

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Message-ID: <2b1dc031-d645-494c-9103-a2bb422ea60b@gmail.com>
Date: Fri, 29 Mar 2024 20:22:14 +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 8:07 PM, Bartosz Golaszewski wrote:
> On Fri, Mar 29, 2024 at 7:56 PM Maximilian Luz <luzmaximilian@...il.com> wrote:
>>
>>
>>
>> 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.
>>
> 
> Both with and without SHM bridge?

With CONFIG_QCOM_TZMEM_MODE_GENERIC=y (and the upcoming fix) everything
works. With CONFIG_QCOM_TZMEM_MODE_SHMBRIDGE=y things unfortunately
still get stuck at boot (regardless of the fix). I think that's
happening even before anything efivar related should come up.

> If so, please Cc me on the fix.

Sure, will do.

Best regards,
Max