linux-kernel - Re: [PATCH AUTOSEL 5.19 05/58] arm64: kernel: drop unnecessary PoC cache clean+invalidate

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Message-ID: <YvJopiTwMaahZGIy@sashalap>
Date:   Tue, 9 Aug 2022 10:01:10 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Anshuman Khandual <anshuman.khandual@....com>,
        Will Deacon <will@...nel.org>, catalin.marinas@....com,
        bp@...e.de, Jason@...c4.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH AUTOSEL 5.19 05/58] arm64: kernel: drop unnecessary PoC
 cache clean+invalidate

On Mon, Aug 08, 2022 at 11:05:29AM +0200, Ard Biesheuvel wrote:
>On Mon, 8 Aug 2022 at 03:31, Sasha Levin <sashal@...nel.org> wrote:
>>
>> From: Ard Biesheuvel <ardb@...nel.org>
>>
>> [ Upstream commit 2e945851e26836c0f2d34be3763ddf55870e49fe ]
>>
>> Some early boot code runs before the virtual placement of the kernel is
>> finalized, and we used to go back to the very start and recreate the ID
>> map along with the page tables describing the virtual kernel mapping,
>> and this involved setting some global variables with the caches off.
>>
>> In order to ensure that global state created by the KASLR code is not
>> corrupted by the cache invalidation that occurs in that case, we needed
>> to clean those global variables to the PoC explicitly.
>>
>> This is no longer needed now that the ID map is created only once (and
>> the associated global variable updates are no longer repeated). So drop
>> the cache maintenance that is no longer necessary.
>>
>> Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
>> Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>
>> Link: https://lore.kernel.org/r/20220624150651.1358849-9-ardb@kernel.org
>> Signed-off-by: Will Deacon <will@...nel.org>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>
>NAK
>
>This patch *must* *not* be backported. It will break the boot.

Appologies for this one, this was a technical issue on my end and I owe
a beer for yourself and few other folks that should have been filtered
out.

I'll drop all your patches from the AUTOSEL queue.

-- 
Thanks,
Sasha