On Wed, Feb 16, 2022 at 2:55 PM Yong Wu [off-list ref] wrote:

On Thu, 2022-01-27 at 12:08 +0100, AngeloGioacchino Del Regno wrote:

quoted

Il 25/01/22 09:56, Yong Wu ha scritto:

quoted

No need zero for the protect buffer that is only accessed by the
IOMMU HW
translation fault happened.

Signed-off-by: Yong Wu <yong.wu@mediatek.com>

I would rather keep this a devm_kzalloc instead... the cost is very
minimal and
this will be handy when new hardware will be introduced, as it may
require a bigger
buffer: in that case, "older" platforms will use only part of it and
we may get
garbage data at the end.

Currently this is to avoid zero 512 bytes for all the platforms.

Sorry, I don't understand why it is unnecessary when the new hardware
requires a bigger buffer. If the buffer becomes bigger, then clearing
it to 0 need more cost. then this patch is more helpful?

The content in this buffer is garbage, we won't care about or analyse
it.

I think we should zero it for security reasons regardless of any other
aspects. With this patch it's leaking kernel data to the hardware.

At the same time, we're talking here about something executed just 1
time when the driver probes. I don't think the cost would really
matter.

Best regards,
Tomasz