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Date: Mon, 16 Oct 2017 15:26:22 +0100 From: Mark Rutland <mark.rutland@....com> To: Robin Murphy <robin.murphy@....com> Cc: Leo Yan <leo.yan@...aro.org>, 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 Mon, Oct 16, 2017 at 03:12:45PM +0100, Robin Murphy wrote: > 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. Sure, I also looked it up. ;) I meant that I couldn't immediately see why VMAP'd stacks were likely to tickle issues with that more reliably. Thanks, Mark.
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