linux-kernel - Re: [PATCH 4.9 00/25] 4.9.316-rc1 review

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Date:   Tue, 24 May 2022 17:06:06 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Jon Hunter <jonathanh@...dia.com>
Cc:     Ard Biesheuvel <ardb@...nel.org>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, torvalds@...ux-foundation.org,
        akpm@...ux-foundation.org, linux@...ck-us.net, shuah@...nel.org,
        patches@...nelci.org, lkft-triage@...ts.linaro.org, pavel@...x.de,
        f.fainelli@...il.com, sudipm.mukherjee@...il.com,
        slade@...dewatkins.com,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH 4.9 00/25] 4.9.316-rc1 review

On Tue, May 24, 2022 at 03:55:58PM +0100, Jon Hunter wrote:
> 
> 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.

These patches are quite small, and just enable it for this known-broken
cpu type.

If there is an issue enabling it for this cpu type, then we can work on
that upstream, but there shouldn't be a reason to prevent this from
being merged now, especially given that it is supposed to be fixing a
known issue.

thanks,

greg k-h