linux-kernel - Re: [RFC v2 0/5] arm64: kvm: reset hyp context for kexec

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Date:	Mon, 30 Mar 2015 17:54:29 +0900
From:	AKASHI Takahiro <takahiro.akashi@...aro.org>
To:	Marc Zyngier <marc.zyngier@....com>
CC:	Kyle McMartin <kmcmarti@...hat.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	Mark Rutland <Mark.Rutland@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	"geoff@...radead.org" <geoff@...radead.org>,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"broonie@...nel.org" <broonie@...nel.org>,
	"david.griego@...aro.org" <david.griego@...aro.org>,
	"christoffer.dall@...aro.org" <christoffer.dall@...aro.org>,
	"freddy77@...il.com" <freddy77@...il.com>
Subject: Re: [RFC v2 0/5] arm64: kvm: reset hyp context for kexec

On 03/30/2015 04:16 PM, Marc Zyngier wrote:
> On Mon, 30 Mar 2015 02:39:53 +0100
> AKASHI Takahiro <takahiro.akashi@...aro.org> wrote:
>
>> On 03/28/2015 02:40 AM, Kyle McMartin wrote:
>>> On Fri, Mar 27, 2015 at 03:37:04PM +0000, Marc Zyngier wrote:
>>>>> [  236.260863] Kernel panic - not syncing: HYP panic:
>>>>> [  236.260863] PS:600003c9 PC:000003ffffff0830 ESR:0000000096000006
>>>>
>>>> It would be interesting if you could find out what you have at offset
>>>> 0x830 of hyp-init.o (the stack trace is for EL1, and is not going to
>>>> help much).
>>>>
>>>
>>> Given the alignment, i'm going to assume i'm looking at the right thing:
>>>
>>> 0000000000000820 <__kvm_hyp_reset>:
>>>        820:       d51c2000        msr     ttbr0_el2, x0
>>>        824:       d5033fdf        isb
>>>        828:       d50c871f        tlbi    alle2
>>>        82c:       d5033f9f        dsb     sy
>>>        830:       10000060        adr     x0, 83c <__kvm_hyp_reset+0x1c>
>>>        834:       b3403c01        bfxil   x1, x0, #0, #16
>>>        838:       d61f0020        br      x1
>>>        83c:       d53c1000        mrs     x0, sctlr_el2
>>>
>>> but it seems fairly implausible to be trapping on ADR x0, 1f...
>>
>>
>> I've never seen this panic on fast model...
>>
>> ESR shows that
>>     - Exception class: Data abort taken without a change in Exception level
>>     - Data fault status code: Translation fault at EL2
>>
>> and FAR seems not to be a proper address.
>
> ... which is consistent with what we're seeing here (data fault on
> something that doesn't generate a load/store). I'm pretty sure the
> page tables are screwed.
>
> Have you tested it with 64k pages?

Hmm... It seems that I was able to reproduce the problem if 64k pages enabled.

-Takahiro AKASHI

> Thanks,
>
>          M.
>
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