linux-kernel - Re: [GIT PULL] parisc huge page support for v4.4

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Date:	Tue, 24 Nov 2015 13:43:50 -0500 (EST)
From:	Mikulas Patocka <mpatocka@...hat.com>
To:	Helge Deller <deller@....de>
cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-parisc@...r.kernel.org,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	John David Anglin <dave.anglin@...l.net>
Subject: Re: [GIT PULL] parisc huge page support for v4.4



On Tue, 24 Nov 2015, Helge Deller wrote:

> * Mikulas Patocka <mpatocka@...hat.com>:
> > 
> > 
> > On Tue, 24 Nov 2015, Helge Deller wrote:
> > 
> > > > Hi
> > > > 
> > > > Since the kernel 4.4-rc2 I'm getting frequent boot failures on PA-RISC. 
> > > > When I revert this patchset, the crashes are gone.
> > > 
> > > > [    3.296666] CPU(s): 4 out of 4 PA8900 (Shortfin) at 1000.000000 MHz online
> > > 
> > > Hi Mikulas,
> > > 
> > > Yes, I've seen this as well.
> > > It affects only the PA8900 CPUs, while all PA8500-PA8700 machines seem to work fine.
> > > I do have a temporary 3-line patch to avoid the crashes which I'll push to my tree shortly.
> > > I'm still investigating why it only affects the PA8900 CPUs, but I assume
> > > it's related to the cache aliasing of those CPUs.
> > > I'll keep you updated.
> > > 
> > > Helge
> > 
> > The PA-RISC specification doesn't allow aliasing on non-equaivalent 
> > addresses. Can the kernel map a piece of kernel data to other virtual 
> > address? If yes, we can't use big pages to map kernel data.
> 
> Can you please try the two patches below?
> The first one disables mapping kernel text/data on huge pages on
> PA8800/PA8900 CPUs. Patch works for me on my Mako PA8800.
> 
> Independend of my huge page patch the second patch disables the tlb
> flush optimization we added earlier. It seems calling flush_tlb_all()
> doesn't reliably flushes tlbs on all CPUs so it's better to fall back to
> the loop implementation.
> 
> Helge

The kernel with these patches works fine so far.

Mikulas
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