From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 675762E11DD for ; Thu, 18 Dec 2025 16:57:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766077056; cv=none; b=RdEGdWdI1DH7qJWwbc96lvQpNPiMUwQBxcIY1dufwX/tP8opeZf+X0VHqjHVTKFzt3cVPEqHkHodKTwmKhBDIEXEpVdXdztjGSfHbOvIH0hWQmrIfc7ehrZBw8Rw5R61Ku4Q8gmvjOLFuD9GzCPUBc896of6AdBj0Ybv/1sPT8k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766077056; c=relaxed/simple; bh=LlWypiomcFVsRX20LhzmxjNTF1H3ODYMFDy4YKZklUM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=rhODVeZtsLhhfLzpLUtaqQitbzG3Al1bkcs2VzLxrqv6EVy0TxTgYyRjloi/j2wB49rENbqB3ssyxEvKI6jWw5ef9e2t4jOwoyRCTcaQw4L6Hql7BWfWfF4kWobSJyBpJGo+Gp+tyzdgLD/92xetMSD8kqMgjITC4oeLUWO1yhc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 56335FEC; Thu, 18 Dec 2025 08:57:25 -0800 (PST) Received: from [10.1.29.42] (e122027.cambridge.arm.com [10.1.29.42]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3CB143F73F; Thu, 18 Dec 2025 08:57:30 -0800 (PST) Message-ID: <0939a54e-dc35-434b-9dbc-06837f04e62f@arm.com> Date: Thu, 18 Dec 2025 16:57:28 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] drm/panthor: Evict groups before VM termination To: Ketil Johnsen , Boris Brezillon , Liviu Dudau , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Grant Likely , Heiko Stuebner Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20251218162644.828495-1-ketil.johnsen@arm.com> From: Steven Price Content-Language: en-GB In-Reply-To: <20251218162644.828495-1-ketil.johnsen@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 18/12/2025 16:26, Ketil Johnsen wrote: > Ensure all related groups are evicted and suspended before VM > destruction takes place. > > This fixes an issue where panthor_vm_destroy() destroys and unmaps the > heap context while there are still on slot groups using this. > The FW will do a write out to the heap context when a CSG (group) is > suspended, so a premature unmap of the heap context will cause a > GPU page fault. > This page fault is quite harmless, and do not affect the continued > operation of the GPU. > > Fixes: 647810ec2476 ("drm/panthor: Add the MMU/VM logical block") > Co-developed-by: Boris Brezillon > Signed-off-by: Ketil Johnsen > --- > drivers/gpu/drm/panthor/panthor_mmu.c | 4 ++++ > drivers/gpu/drm/panthor/panthor_sched.c | 16 ++++++++++++++++ > drivers/gpu/drm/panthor/panthor_sched.h | 1 + > 3 files changed, 21 insertions(+) > > diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c > index 74230f7199121..0e4b301a9c70e 100644 > --- a/drivers/gpu/drm/panthor/panthor_mmu.c > +++ b/drivers/gpu/drm/panthor/panthor_mmu.c > @@ -1537,6 +1537,10 @@ static void panthor_vm_destroy(struct panthor_vm *vm) > > vm->destroyed = true; > > + /* Tell scheduler to stop all GPU work related to this VM */ > + if (refcount_read(&vm->as.active_cnt) > 0) > + panthor_sched_prepare_for_vm_destruction(vm->ptdev); > + > mutex_lock(&vm->heaps.lock); > panthor_heap_pool_destroy(vm->heaps.pool); > vm->heaps.pool = NULL; > diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c > index f680edcd40aad..fbbaab9b25efb 100644 > --- a/drivers/gpu/drm/panthor/panthor_sched.c > +++ b/drivers/gpu/drm/panthor/panthor_sched.c > @@ -2930,6 +2930,22 @@ void panthor_sched_report_mmu_fault(struct panthor_device *ptdev) > sched_queue_delayed_work(ptdev->scheduler, tick, 0); > } > > +void panthor_sched_prepare_for_vm_destruction(struct panthor_device *ptdev) > +{ > + /* FW can write out internal state, like the heap context, during CSG > + * suspend. It is therefore important that the scheduler has fully > + * evicted any pending and related groups before VM destruction can > + * safely continue. Failure to do so can lead to GPU page faults. > + * A controlled termination of a Panthor instance involves destroying > + * the group(s) before the VM. This means any relevant group eviction > + * has already been initiated by this point, and we just need to > + * ensure that any pending tick_work() has been completed. > + */ > + if (ptdev->scheduler) { > + flush_work(&ptdev->scheduler->tick_work.work); > + } NIT: braces not needed. But I'm also struggling to understand in what situation ptdev->scheduler would be NULL? Thanks, Steve > +} > + > void panthor_sched_resume(struct panthor_device *ptdev) > { > /* Force a tick to re-evaluate after a resume. */ > diff --git a/drivers/gpu/drm/panthor/panthor_sched.h b/drivers/gpu/drm/panthor/panthor_sched.h > index f4a475aa34c0a..9a8692de8aded 100644 > --- a/drivers/gpu/drm/panthor/panthor_sched.h > +++ b/drivers/gpu/drm/panthor/panthor_sched.h > @@ -50,6 +50,7 @@ void panthor_sched_suspend(struct panthor_device *ptdev); > void panthor_sched_resume(struct panthor_device *ptdev); > > void panthor_sched_report_mmu_fault(struct panthor_device *ptdev); > +void panthor_sched_prepare_for_vm_destruction(struct panthor_device *ptdev); > void panthor_sched_report_fw_events(struct panthor_device *ptdev, u32 events); > > void panthor_fdinfo_gather_group_samples(struct panthor_file *pfile);