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 20:07:09 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Maximilian Luz <luzmaximilian@...il.com>
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 Fri, Mar 29, 2024 at 7:56 PM Maximilian Luz <luzmaximilian@...ilcom> 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?

If so, please Cc me on the fix.

Bart