linux-kernel - Re: [PATCH 3.13.y-ckt 71/80] MIPS: Fix C0

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Date:	Fri, 20 Mar 2015 10:02:58 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	David Daney <ddaney@...iumnetworks.com>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com, David Daney <david.daney@...ium.com>,
	Leonid Yegoshin <Leonid.Yegoshin@...tec.com>,
	linux-mips@...ux-mips.org, Ralf Baechle <ralf@...ux-mips.org>
Subject: Re: [PATCH 3.13.y-ckt 71/80] MIPS: Fix C0_Pagegrain[IEC] support.

On Thu, 2015-03-19 at 16:10 -0700, David Daney wrote:
> On 03/19/2015 03:35 PM, Kamal Mostafa wrote:
> > 3.13.11-ckt17 -stable review patch.  If anyone has any objections, please let me know.
> >
> 
> Read the patch commentary.  It should only be applied to 3.17 and later.
> 
> So:  NACK.
> 

Thanks very much for reviewing this, David.  Dropped from 3.13-stable.

Also FYI, if you append e.g. "# 3.17+" to your Cc: stable line, that
will help the stable maintainers (more specifically, will help our
automated tools ;-) recognize where the patch should and shouldn't be
applied.  Example:

    Cc: <stable@...r.kernel.org> # 3.17+

 -Kamal


> > ------------------
> >
> > From: David Daney <david.daney@...ium.com>
> >
> > commit 9ead8632bbf454cfc709b6205dc9cd8582fb0d64 upstream.
> >
> > The following commits:
> >
> >    5890f70f15c52d (MIPS: Use dedicated exception handler if CPU supports RI/XI exceptions)
> >    6575b1d4173eae (MIPS: kernel: cpu-probe: Detect unique RI/XI exceptions)
> >
> > break the kernel for *all* existing MIPS CPUs that implement the
> > CP0_PageGrain[IEC] bit.  They cause the TLB exception handlers to be
> > generated without the legacy execute-inhibit handling, but never set
> > the CP0_PageGrain[IEC] bit to activate the use of dedicated exception
> > vectors for execute-inhibit exceptions.  The result is that upon
> > detection of an execute-inhibit violation, we loop forever in the TLB
> > exception handlers instead of sending SIGSEGV to the task.
> >
> > If we are generating TLB exception handlers expecting separate
> > vectors, we must also enable the CP0_PageGrain[IEC] feature.
> >
> > The bug was introduced in kernel version 3.17.
> >
> > Signed-off-by: David Daney <david.daney@...ium.com>
> > Cc: Leonid Yegoshin <Leonid.Yegoshin@...tec.com>
> > Cc: linux-mips@...ux-mips.org
> > Patchwork: http://patchwork.linux-mips.org/patch/8880/
> > Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>
> > Signed-off-by: Kamal Mostafa <kamal@...onical.com>
> > ---
> >   arch/mips/mm/tlb-r4k.c | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/arch/mips/mm/tlb-r4k.c b/arch/mips/mm/tlb-r4k.c
> > index da3b0b9..d04fe4e 100644
> > --- a/arch/mips/mm/tlb-r4k.c
> > +++ b/arch/mips/mm/tlb-r4k.c
> > @@ -429,6 +429,8 @@ void tlb_init(void)
> >   #ifdef CONFIG_64BIT
> >   		pg |= PG_ELPA;
> >   #endif
> > +		if (cpu_has_rixiex)
> > +			pg |= PG_IEC;
> >   		write_c0_pagegrain(pg);
> >   	}
> >
> >
> 


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