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

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Message-ID: <23c8a80d-a816-455b-b5ab-d65b159fd90f@amd.com>
Date: Thu, 18 Apr 2024 14:25:59 +0200
From: Christian König <christian.koenig@....com>
To: Zack Rusin <zack.rusin@...adcom.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 haven't seen your reply. Feel free to add my rb to the patch.

Regards,
Christian.

Am 18.04.24 um 13:38 schrieb Zack Rusin:
> Ping on this one. If we don't want the "_once" then I can quickly
> prepare a patch that just removes the logging altogether, because
> while useful it's polluting up the kernel logs too much right now so
> getting a fix in for 6.9 for this would be great.
>
> z
>
> On Mon, Apr 8, 2024 at 1:46 PM Zack Rusin <zack.rusin@...adcom.com> wrote:
>> 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