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From: Mark Rutland <mark.rutland@arm.com>
To: AKASHI Takahiro <takahiro.akashi@linaro.org>,
	geoff@infradead.org, catalin.marinas@arm.com,
	will.deacon@arm.com, james.morse@arm.com,
	bauerman@linux.vnet.ibm.com, dyoung@redhat.com,
	kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v31 05/12] arm64: kdump: protect crash dump kernel memory
Date: Fri, 3 Feb 2017 11:51:59 +0000	[thread overview]
Message-ID: <20170203115158.GD30497@leverpostej> (raw)
In-Reply-To: <20170203014538.GA29585@linaro.org>

Hi,

On Fri, Feb 03, 2017 at 10:45:39AM +0900, AKASHI Takahiro wrote:
> On Thu, Feb 02, 2017 at 11:54:25AM +0000, Mark Rutland wrote:
> > On Thu, Feb 02, 2017 at 07:39:06PM +0900, AKASHI Takahiro wrote:
> > > On Wed, Feb 01, 2017 at 06:25:06PM +0000, Mark Rutland wrote:
> > > > On Wed, Feb 01, 2017 at 06:00:08PM +0000, Mark Rutland wrote:
> > > > Another question is (how) does hyp map this region?
> > > 
> > > I don't get your point here.
> > > Hyp mode does care only physical memory in intermediate address, doesn't it?
> > 
> > My concern was that hyp may map the region; and thus buggy code at hyp
> > can corrupt the region (and/or hyp may conflict w.r.t. attributes).
> 
> Grep'ing create_hyp_mappings() under arch/arm(64)/kvm shows that
> we have only a few small regions of memory mapped in hyp mode.
> I also confirmed that there is no active mapping for crash dump kernel
> memory by checking mmu tables with DS-5 debugger.

Ok, that sounds fine.

I was under the mistaken impression that hyp had a copy of the whole
linear mapping, but it seems it lazily maps that in (at page
granularity) as required. So there should be no alias for the
crashkernel region.

> > We mght have to ensure hyp doesn't map the crashkernel region, and to
> > case us pain, disallow freeing of any part of the region.
> 
> So I don't believe we need to worry such a case.

I agree.

Thanks,
Mark.

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WARNING: multiple messages have this Message-ID (diff)
From: mark.rutland@arm.com (Mark Rutland)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v31 05/12] arm64: kdump: protect crash dump kernel memory
Date: Fri, 3 Feb 2017 11:51:59 +0000	[thread overview]
Message-ID: <20170203115158.GD30497@leverpostej> (raw)
In-Reply-To: <20170203014538.GA29585@linaro.org>

Hi,

On Fri, Feb 03, 2017 at 10:45:39AM +0900, AKASHI Takahiro wrote:
> On Thu, Feb 02, 2017 at 11:54:25AM +0000, Mark Rutland wrote:
> > On Thu, Feb 02, 2017 at 07:39:06PM +0900, AKASHI Takahiro wrote:
> > > On Wed, Feb 01, 2017 at 06:25:06PM +0000, Mark Rutland wrote:
> > > > On Wed, Feb 01, 2017 at 06:00:08PM +0000, Mark Rutland wrote:
> > > > Another question is (how) does hyp map this region?
> > > 
> > > I don't get your point here.
> > > Hyp mode does care only physical memory in intermediate address, doesn't it?
> > 
> > My concern was that hyp may map the region; and thus buggy code at hyp
> > can corrupt the region (and/or hyp may conflict w.r.t. attributes).
> 
> Grep'ing create_hyp_mappings() under arch/arm(64)/kvm shows that
> we have only a few small regions of memory mapped in hyp mode.
> I also confirmed that there is no active mapping for crash dump kernel
> memory by checking mmu tables with DS-5 debugger.

Ok, that sounds fine.

I was under the mistaken impression that hyp had a copy of the whole
linear mapping, but it seems it lazily maps that in (at page
granularity) as required. So there should be no alias for the
crashkernel region.

> > We mght have to ensure hyp doesn't map the crashkernel region, and to
> > case us pain, disallow freeing of any part of the region.
> 
> So I don't believe we need to worry such a case.

I agree.

Thanks,
Mark.

  reply	other threads:[~2017-02-03 11:51 UTC|newest]

Thread overview: 92+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-02-01 12:42 [PATCH v31 00/12] add kdump support AKASHI Takahiro
2017-02-01 12:42 ` AKASHI Takahiro
2017-02-01 12:45 ` [PATCH v31 01/12] memblock: add memblock_cap_memory_range() AKASHI Takahiro
2017-02-01 12:45   ` AKASHI Takahiro
2017-02-01 12:45   ` AKASHI Takahiro
2017-02-01 12:46 ` [PATCH v31 02/12] arm64: limit memory regions based on DT property, usable-memory-range AKASHI Takahiro
2017-02-01 12:46   ` AKASHI Takahiro
2017-02-01 15:07   ` Mark Rutland
2017-02-01 15:07     ` Mark Rutland
2017-02-02  4:21     ` AKASHI Takahiro
2017-02-02  4:21       ` AKASHI Takahiro
2017-02-01 12:46 ` [PATCH v31 03/12] arm64: kdump: reserve memory for crash dump kernel AKASHI Takahiro
2017-02-01 12:46   ` AKASHI Takahiro
2017-02-01 15:26   ` Mark Rutland
2017-02-01 15:26     ` Mark Rutland
2017-02-02  4:52     ` AKASHI Takahiro
2017-02-02  4:52       ` AKASHI Takahiro
2017-02-02 11:26       ` Mark Rutland
2017-02-02 11:26         ` Mark Rutland
2017-02-02 13:44         ` AKASHI Takahiro
2017-02-02 13:44           ` AKASHI Takahiro
2017-02-01 12:46 ` [PATCH v31 04/12] arm64: mm: allow for unmapping part of kernel mapping AKASHI Takahiro
2017-02-01 12:46   ` AKASHI Takahiro
2017-02-01 16:03   ` Mark Rutland
2017-02-01 16:03     ` Mark Rutland
2017-02-02 10:21     ` AKASHI Takahiro
2017-02-02 10:21       ` AKASHI Takahiro
2017-02-02 11:44       ` Mark Rutland
2017-02-02 11:44         ` Mark Rutland
2017-02-02 14:01         ` AKASHI Takahiro
2017-02-02 14:01           ` AKASHI Takahiro
2017-02-02 14:35           ` Mark Rutland
2017-02-02 14:35             ` Mark Rutland
2017-02-02 14:55             ` AKASHI Takahiro
2017-02-02 14:55               ` AKASHI Takahiro
2017-02-03  6:13               ` AKASHI Takahiro
2017-02-03  6:13                 ` AKASHI Takahiro
2017-02-03 14:22                 ` Mark Rutland
2017-02-03 14:22                   ` Mark Rutland
2017-02-01 12:46 ` [PATCH v31 05/12] arm64: kdump: protect crash dump kernel memory AKASHI Takahiro
2017-02-01 12:46   ` AKASHI Takahiro
2017-02-01 18:00   ` Mark Rutland
2017-02-01 18:00     ` Mark Rutland
2017-02-01 18:25     ` Mark Rutland
2017-02-01 18:25       ` Mark Rutland
2017-02-02 10:39       ` AKASHI Takahiro
2017-02-02 10:39         ` AKASHI Takahiro
2017-02-02 11:54         ` Mark Rutland
2017-02-02 11:54           ` Mark Rutland
2017-02-03  1:45           ` AKASHI Takahiro
2017-02-03  1:45             ` AKASHI Takahiro
2017-02-03 11:51             ` Mark Rutland [this message]
2017-02-03 11:51               ` Mark Rutland
2017-02-02 10:45       ` James Morse
2017-02-02 10:45         ` James Morse
2017-02-02 11:19         ` AKASHI Takahiro
2017-02-02 11:19           ` AKASHI Takahiro
2017-02-02 11:48         ` Mark Rutland
2017-02-02 11:48           ` Mark Rutland
2017-02-02 10:31     ` AKASHI Takahiro
2017-02-02 10:31       ` AKASHI Takahiro
2017-02-02 11:16       ` Mark Rutland
2017-02-02 11:16         ` Mark Rutland
2017-02-02 14:36         ` AKASHI Takahiro
2017-02-02 14:36           ` AKASHI Takahiro
2017-02-02 15:36           ` Mark Rutland
2017-02-02 15:36             ` Mark Rutland
2017-02-01 12:46 ` [PATCH v31 06/12] arm64: hibernate: preserve kdump image around hibernation AKASHI Takahiro
2017-02-01 12:46   ` AKASHI Takahiro
2017-02-01 12:46 ` [PATCH v31 07/12] arm64: kdump: implement machine_crash_shutdown() AKASHI Takahiro
2017-02-01 12:46   ` AKASHI Takahiro
2017-02-01 12:46 ` [PATCH v31 08/12] arm64: kdump: add VMCOREINFO's for user-space tools AKASHI Takahiro
2017-02-01 12:46   ` AKASHI Takahiro
2017-02-01 12:46 ` [PATCH v31 09/12] arm64: kdump: provide /proc/vmcore file AKASHI Takahiro
2017-02-01 12:46   ` AKASHI Takahiro
2017-02-01 19:21   ` Mark Rutland
2017-02-01 19:21     ` Mark Rutland
2017-02-02  6:24     ` AKASHI Takahiro
2017-02-02  6:24       ` AKASHI Takahiro
2017-02-02 12:03       ` Mark Rutland
2017-02-02 12:03         ` Mark Rutland
2017-02-02 12:08         ` Mark Rutland
2017-02-02 12:08           ` Mark Rutland
2017-02-02 14:39           ` AKASHI Takahiro
2017-02-02 14:39             ` AKASHI Takahiro
2017-02-01 12:46 ` [PATCH v31 10/12] arm64: kdump: enable kdump in defconfig AKASHI Takahiro
2017-02-01 12:46   ` AKASHI Takahiro
2017-02-01 12:46 ` [PATCH v31 11/12] Documentation: kdump: describe arm64 port AKASHI Takahiro
2017-02-01 12:46   ` AKASHI Takahiro
2017-02-01 12:48 ` [PATCH v31 12/12] Documentation: dt: chosen properties for arm64 kdump AKASHI Takahiro
2017-02-01 12:48   ` AKASHI Takahiro
2017-02-01 12:48   ` AKASHI Takahiro

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