linux-kernel - Re: ARM64: Regression with commit e3067861ba66 ("arm64: add basic VMAP

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Date:   Mon, 16 Oct 2017 15:12:45 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Mark Rutland <mark.rutland@....com>, Leo Yan <leo.yan@...aro.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        ard.biesheuvel@...aro.org
Subject: Re: ARM64: Regression with commit e3067861ba66 ("arm64: add basic
 VMAP_STACK support")

On 16/10/17 14:48, Mark Rutland wrote:
> Hi Leo,
> 
> On Mon, Oct 16, 2017 at 09:17:23AM +0800, Leo Yan wrote:
>> On Tue, Oct 10, 2017 at 05:03:44PM +0100, Robin Murphy wrote:
>>> On 10/10/17 16:45, Mark Rutland wrote:
>>>> On Tue, Oct 10, 2017 at 10:27:25PM +0800, Leo Yan wrote:
>>>>> I work mainline kernel on Hikey620 board, I find it's easily to
>>>>> introduce the panic and report the log as below. So I bisect the kernel
>>>>> and finally narrow down the commit e3067861ba66 ("arm64: add basic
>>>>> VMAP_STACK support") which introduce this issue.
>>>>>
>>>>> I tried to remove 'select HAVE_ARCH_VMAP_STACK' from
>>>>> arch/arm64/Kconfig, then I can see the panic issue will dismiss. So
>>>>> could you check this and have insight for this issue?
>>>>
>>>> Given the stuff in the backtrace, my suspicion is something is trying to
>>>> perform DMA to/from the stack, getting junk addresses form the attempted
>>>> virt<->phys conversions.
>>>>
>>>> Could you try enabling both VMAP_STACK and CONFIG_DEBUG_VIRTUAL?
>>>
>>> CONFIG_DMA_API_DEBUG should scream about drivers trying to use stack
>>> addresses either way, too.
>>
>> Thanks for suggestions, Mark & Robin.
>>
>> I enabled these debugging configs but cannot get clue from it; but
>> occasionally found this issue is quite likely related with CA53 errata,
>> especialy ERRATA_A53_855873 is the relative one. So I changed to use
>> ARM-TF mainline code with ERRATA fixing, this issue can be dismissed.
> 
> Thanks for the update.
> 
> Just to confirm, with the updated firmware you no longer see the issue?
> 
> I can't immediately see how that would be related.

Cores up to r0p2 have the other errata to which
ARM64_WORKAROUND_CLEAN_CACHE also applies anyway; r3p0+ have an ACTLR
bit to do thee CVAC->CIVAC upgrade in hardware, and our policy is that
we expect firmware to enable such hardware workarounds where possible. I
assume that's why we don't explicitly document 855873 anywhere in Linux.

Robin.