From: will.deacon@arm•com (Will Deacon)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] arm64: efi: don't restore TTBR0 if active_mm points at init_mm
Date: Mon, 23 Mar 2015 18:00:16 +0000 [thread overview]
Message-ID: <20150323180016.GE1556@arm.com> (raw)
In-Reply-To: <20150323175055.GD12757@e104818-lin.cambridge.arm.com>
On Mon, Mar 23, 2015 at 05:50:55PM +0000, Catalin Marinas wrote:
> On Mon, Mar 23, 2015 at 05:22:57PM +0000, Jon Medhurst (Tixy) wrote:
> > On Mon, 2015-03-23 at 15:44 +0000, Catalin Marinas wrote:
> > > From 5d9e3540b6480558528612dd3672543fa8ab3528 Mon Sep 17 00:00:00 2001
> > > From: Catalin Marinas <catalin.marinas@arm•com>
> > > Date: Mon, 23 Mar 2015 15:06:50 +0000
> > > Subject: [PATCH] arm64: Use the reserved TTBR0 if context switching to the
> > > init_mm
> > >
> > > The idle_task_exit() function may call switch_mm() with next ==
> > > &init_mm. On arm64, init_mm.pgd cannot be used for user mappings, so
> > > this patch simply sets the reserved TTBR0.
> > >
> > > Cc: <stable@vger•kernel.org>
> > > Reported-by: Jon Medhurst (Tixy) <tixy@linaro•org>
> > > Signed-off-by: Catalin Marinas <catalin.marinas@arm•com>
> >
> > That unsurprising fixes the BUG_ON I was seeing on Juno, so...
> > Tested-by: Jon Medhurst (Tixy) <tixy@linaro•org>
>
> Thanks.
>
> > One question, is bypassing setting the mm_cpumask and context.id for
> > init_mm OK? I'm not familiar with the code but had a quick look, and it
> > looks like they are just used for ASID management, in which case I
> > assume everything is OK - ASIDs only being relevant for user mappings in
> > ttbr0?
>
> That's my thinking as well. Will asked me the same question, so I'll let
> him confirm if he's seeing anything wrong.
I can't seem to break it. The ASID state should all be up to date with the
previous mm, so this should be harmless...
Will
prev parent reply other threads:[~2015-03-23 18:00 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-19 15:43 [PATCH] arm64: efi: don't restore TTBR0 if active_mm points at init_mm Will Deacon
2015-03-19 16:01 ` Ard Biesheuvel
2015-03-23 13:22 ` Jon Medhurst (Tixy)
2015-03-23 15:44 ` Catalin Marinas
2015-03-23 17:22 ` Jon Medhurst (Tixy)
2015-03-23 17:50 ` Catalin Marinas
2015-03-23 18:00 ` Will Deacon [this message]
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