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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Fri, 30 Sep 2022 12:35:45 -0700
Message-ID: <CAHk-=wgPqauyKD9CoQg2AAtV=ygpS_fAahhgzPAe99k5Kush6A@mail.gmail.com>
Subject: Re: [PATCH 07/10] crypto: Use ARCH_DMA_MINALIGN instead of ARCH_KMALLOC_MINALIGN
To:     Catalin Marinas <catalin.marinas@arm.com>
Cc:     Isaac Manjarres <isaacmanjarres@google.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Ard Biesheuvel <ardb@kernel.org>,
        Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Saravana Kannan <saravanak@google.com>, kernel-team@android.com
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On Fri, Sep 30, 2022 at 11:33 AM Catalin Marinas
<catalin.marinas@arm.com> wrote:
>
> I started refreshing the series but I got stuck on having to do bouncing
> for small buffers even if when they go through the iommu (and I don't
> have the set up to test it yet).

May I suggest doing that "force bouncing" and "change kmalloc to have
a 8-byte minalign" to be the two first commits?

IOW, if we force bouncing for unaligned DMA, then that *should* mean
that allocation alignment is no longer a correctness issue, it's
purely a performance one due to the bouncing.

So then the rest of the series should be about "ok, this is actually a
hot enough allocation that I want to force alignment", and be purely
about performance, not correctness.

No?

               Linus