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

[Jon Hunter]

On 24/05/2022 16:06, Greg Kroah-Hartman wrote:
> 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.

Yes understand. I have been doing some more testing and with v4.9, this 
is triggering a boot timeout 100% of the time. So with 20 boots, all 20 
timeout. Note the timeout is 2 mins. With v4.14, I saw only 5 out of 20 
timeouts and so it would seem that v4.9 is slower to boot in general. I 
think that the more recent kernels show intermittent timeouts.

We have some verbose logging enabled on this platform, which until now 
has not been a problem, but I will disable this and that should resolve 
this for now.

Cheers
Jon	

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nvpublic