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Date:   Tue, 24 May 2022 15:55:58 +0100
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From:   Jon Hunter <jonathanh@nvidia.com>
Subject: Re: [PATCH 4.9 00/25] 4.9.316-rc1 review
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Ard Biesheuvel <ardb@kernel.org>
Cc:     linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        torvalds@linux-foundation.org, akpm@linux-foundation.org,
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On 24/05/2022 13:09, Greg Kroah-Hartman wrote:

...

>> I am seeing a boot regression on tegra124-jetson-tk1 and reverting the above
>> commit is fixing the problem. This also appears to impact linux-4.14.y,
>> 4.19.y and 5.4.y.
>>
>> Test results for stable-v4.9:
>>      8 builds:	8 pass, 0 fail
>>      18 boots:	16 pass, 2 fail
>>      18 tests:	18 pass, 0 fail
>>
>> Linux version:	4.9.316-rc1-gbe4ec3e3faa1
>> Boards tested:	tegra124-jetson-tk1, tegra20-ventana,
>>                  tegra210-p2371-2180, tegra30-cardhu-a04
>>
>> Boot failures:	tegra124-jetson-tk1
> 
> Odd.  This is also in 5.10.y, right?  No issues there?  Are we missing
> something?


Actually, the more I look at this, the more I see various intermittent 
reports with this and it is also impacting the mainline.

The problem is that the commit in question is causing a ton of messages 
to be printed a boot and this sometimes is causing the boot test to fail 
because the boot is taking too long. The console shows ...

[ 1233.327547] CPU0: Spectre BHB: using loop workaround
[ 1233.327795] CPU1: Spectre BHB: using loop workaround
[ 1233.328270] CPU1: Spectre BHB: using loop workaround
[ 1233.328700] CPU1: Spectre BHB: using loop workaround
[ 1233.355477] CPU2: Spectre BHB: using loop workaround
** 7 printk messages dropped **
[ 1233.366271] CPU0: Spectre BHB: using loop workaround
[ 1233.366580] CPU0: Spectre BHB: using loop workaround
[ 1233.366815] CPU1: Spectre BHB: using loop workaround
[ 1233.405475] CPU1: Spectre BHB: using loop workaround
[ 1233.405874] CPU0: Spectre BHB: using loop workaround
[ 1233.406041] CPU1: Spectre BHB: using loop workaround
** 1 printk messages dropped **

There is a similar report of this [0] and I believe that we need a 
similar fix for the above prints as well. I have reported this to Ard 
[1]. So I am not sure that these Spectre BHB patches are quite ready for 
stable.

Cheers
Jon

[0] 
https://lore.kernel.org/linux-arm-kernel/20220519161310.1489625-1-dmitry.osipenko@collabora.com/T/
[1] 
https://lore.kernel.org/linux-arm-kernel/a589f56d-a0e1-328d-e4be-9427342d46b8@nvidia.com/

-- 
nvpublic