linux-kernel - Re: [PATCH] drm/ttm: Print the memory decryption status just once

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Message-ID: <CABQX2QMaF6e6o4Ewg6sExfaEZMXRaUrNHNYUCAYG3+44P=7epQ@mail.gmail.com>
Date: Mon, 8 Apr 2024 13:46:49 -0400
From: Zack Rusin <zack.rusin@...adcom.com>
To: Christian König <christian.koenig@....com>, 
	dri-devel@...ts.freedesktop.org
Cc: Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>, 
	Ian Forbes <ian.forbes@...adcom.com>, Martin Krastev <martin.krastev@...adcom.com>, 
	Maaz Mombasawala <maaz.mombasawala@...adcom.com>, 
	Thomas Hellström <thomas.hellstrom@...ux.intel.com>, 
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] drm/ttm: Print the memory decryption status just once

Sorry, apologies to everyone. By accident I replied off the list.
Redoing it now on the list. More below.

On Mon, Apr 8, 2024 at 12:10 PM Christian König
<christian.koenig@....com> wrote:
>
> Am 08.04.24 um 18:04 schrieb Zack Rusin:
> > On Mon, Apr 8, 2024 at 11:59 AM Christian König
> > <christian.koenig@....com> wrote:
> >> Am 08.04.24 um 17:56 schrieb Zack Rusin:
> >>> Stop printing the TT memory decryption status info each time tt is created
> >>> and instead print it just once.
> >>>
> >>> Reduces the spam in the system logs when running guests with SEV enabled.
> >> Do we then really need this in the first place?
> > Thomas asked for it just to have an indication when those paths are
> > being used because they could potentially break things pretty bad. I
> > think it is useful knowing that those paths are hit (but only once).
> > It makes it pretty easy for me to tell whether bug reports with people
> > who report black screen can be answered with "the kernel needs to be
> > upgraded" ;)
>
> Sounds reasonable, but my expectation was rather that we would print
> something on the device level.
>
> If that's not feasible for whatever reason than printing it once works
> as well of course.

TBH, I think it's pretty convenient to have the drm_info in the TT
just to make sure that when drivers request use_dma_alloc on SEV
systems TT turns decryption on correctly, i.e. it's a nice sanity
check when reading the logs. But if you'd prefer it in the driver I
can move this logic there as well.

z