linux-kernel - Re: CONFIG_THUMB2_KERNEL=y boot failure after Spectre BHB fixes

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Message-ID: <1896453.PYKUYFuaPT@localhost.localdomain>
Date:   Wed, 30 Mar 2022 20:27:56 +0200
From:   Christian Eggers <ceggers@...i.de>
To:     Ard Biesheuvel <ardb@...nel.org>
CC:     "Russell King (Oracle)" <linux@...linux.org.uk>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        <llvm@...ts.linux.dev>, Nathan Chancellor <nathan@...nel.org>
Subject: Re: CONFIG_THUMB2_KERNEL=y boot failure after Spectre BHB fixes

On Wednesday, 30 March 2022, 19:42:31 CEST, Ard Biesheuvel wrote:
> On Wed, 30 Mar 2022 at 19:33, Christian Eggers <ceggers@...i.de> wrote:
> >
> > I just switched to v5.15.31-rt38 which already includes
> > 6c7cb60bff7a ("ARM: fix Thumb2 regression")
> >
> > This kernel boots fine now, even with CONFIG_HARDEN_BRANCH_HISTORY=y. After
> > applying the patch series from Ard, the system still boots fine.
> >
> > I haven't any understanding what these patches do. Is there anything I shall
> > test?
> >
> 
> Thanks for confirming. The first fix affects all Thumb2
> configurations, my patch only affects Thumb2 configurations that
> actually enable the loop8 mitigation for Spectre-BHB.
> 
> What type of CPU are you booting on?
> 

NXP i.MX6ULL (ARM Cortex-A7).