linux-kernel - Re: [PATCH v11 7/9] arm64/kasan: add and use kasan_map

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Message-ID: <CAOAebxv4h+8ej6JA_DZbXaNV5JsAk4MbcCLf1+2RvwKGF2+MxQ@mail.gmail.com>
Date:   Fri, 13 Oct 2017 11:09:41 -0400
From:   Pavel Tatashin <pasha.tatashin@...cle.com>
To:     Will Deacon <will.deacon@....com>
Cc:     linux-kernel@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        x86@...nel.org, kasan-dev@...glegroups.com, borntraeger@...ibm.com,
        heiko.carstens@...ibm.com, davem@...emloft.net,
        willy@...radead.org, Michal Hocko <mhocko@...nel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Mark Rutland <mark.rutland@....com>, catalin.marinas@....com,
        sam@...nborg.org, mgorman@...hsingularity.net,
        Steve Sistare <steven.sistare@...cle.com>,
        daniel.m.jordan@...cle.com, bob.picco@...cle.com
Subject: Re: [PATCH v11 7/9] arm64/kasan: add and use kasan_map_populate()

> It shouldn't be difficult to use section mappings with my patch, I just
> don't really see the need to try to optimise TLB pressure when you're
> running with KASAN enabled which already has something like a 3x slowdown
> afaik. If it ends up being a big deal, we can always do that later, but
> my main aim here is to divorce kasan from vmemmap because they should be
> completely unrelated.

Yes, I understand that kasan makes system slow, but my point is why
make it even slower? However, I am OK adding your patch to the series,
BTW, symmetric changes will be needed for x86 as well sometime later.

>
> This certainly doesn't sound right; mapping the shadow with pages shouldn't
> lead to problems. I also can't seem to reproduce this myself -- could you
> share your full .config and a pointer to the git tree that you're using,
> please?

Config is attached. I am using my patch series + your patch + today's
clone from https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

Also, in a separate e-mail i sent out the qemu arguments.

>
>> I feel, this patch requires more work, and I am troubled with using
>> base pages instead of large pages.
>
> I'm happy to try fixing this, because I think splitting up kasan and vmemmap
> is the right thing to do here.

Thank you very much.

Pavel

Download attachment "config.gz" of type "application/x-gzip" (36799 bytes)