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

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Message-ID: <5515984D.2020801@arm.com>
Date:	Fri, 27 Mar 2015 17:50:05 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Kyle McMartin <kmcmarti@...hat.com>
CC:	AKASHI Takahiro <takahiro.akashi@...aro.org>,
	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 27/03/15 17:40, 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...

... unless you've just switched TTBR0_EL2 to something slightly
inappropriate, and conveniently flushed the TLBs. Also, having 0 as the
exception class is fairly indicative you've fetched some crap, which
reinforce my idea that the page tables are pointing to nowhere-land.

I'll try to review the patches next week, maybe I'll spot something by
inspection.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...
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