Re: [PATCH] drm/amdkfd: Remove vla

From: "Christian König" <christian.koenig@amd.com>
To: Laura Abbott <labbott@redhat.com>,
	Oded Gabbay <oded.gabbay@gmail.com>,
	Alex Deucher <alexander.deucher@amd.com>,
	"David (ChunMing) Zhou" <David1.Zhou@amd.com>
Cc: David Airlie <airlied@linux.ie>,
	dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org,
	linux-kernel@vger.kernel.org,
	kernel-hardening@lists.openwall.com,
	Kees Cook <keescook@chromium.org>
Subject: Re: [PATCH] drm/amdkfd: Remove vla
Date: Tue, 10 Apr 2018 08:38:59 +0200	[thread overview]
Message-ID: <71ff5078-713c-ff8b-8c8d-6d24a7d84c02@amd.com> (raw)
In-Reply-To: <20180409210620.3647-1-labbott@redhat.com>

Am 09.04.2018 um 23:06 schrieb Laura Abbott:
> There's an ongoing effort to remove VLAs[1] from the kernel to eventually
> turn on -Wvla. The single VLA usage in the amdkfd driver is actually
> constant across all current platforms.

Actually that isn't correct.

Could be that we haven't upstreamed KFD support for them, but Vega10 
have a different interrupt ring entry size and so would cause the error 
message here.

> Switch to a constant size array
> instead.

I would say to just make make the array bigger.

Regards,
Christian.

>
> [1] https://lkml.org/lkml/2018/3/7/621
>
> Signed-off-by: Laura Abbott <labbott@redhat.com>
> ---
>   drivers/gpu/drm/amd/amdkfd/kfd_interrupt.c | 8 +++++---
>   1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_interrupt.c b/drivers/gpu/drm/amd/amdkfd/kfd_interrupt.c
> index 035c351f47c5..c9863858f343 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_interrupt.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_interrupt.c
> @@ -139,10 +139,12 @@ static void interrupt_wq(struct work_struct *work)
>   {
>   	struct kfd_dev *dev = container_of(work, struct kfd_dev,
>   						interrupt_work);
> +	uint32_t ih_ring_entry[4];
>   
> -	uint32_t ih_ring_entry[DIV_ROUND_UP(
> -				dev->device_info->ih_ring_entry_size,
> -				sizeof(uint32_t))];
> +	if (dev->device_info->ih_ring_entry_size > (4 * sizeof(uint32_t))) {
> +		dev_err(kfd_chardev(), "Ring entry too small\n");
> +		return;
> +	}
>   
>   	while (dequeue_ih_ring_entry(dev, ih_ring_entry))
>   		dev->device_info->event_interrupt_class->interrupt_wq(dev,