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([2001:df0:0:200c:75aa:d6ca:4354:6033]) by smtp.gmail.com with ESMTPSA id jy18-20020a17090b325200b001e31803540fsm450854pjb.6.2022.06.28.16.09.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 28 Jun 2022 16:09:09 -0700 (PDT) Message-ID: <9f812d3d-0fcd-46e6-6d7e-6d4bf66f24ab@gmail.com> Date: Wed, 29 Jun 2022 11:09:00 +1200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: Re: [PATCH v2 3/3] arch/*/: remove CONFIG_VIRT_TO_BUS Content-Language: en-US To: Arnd Bergmann Cc: Geert Uytterhoeven , scsi , Linux Kernel Mailing List , Arnd Bergmann , Jakub Kicinski , Christoph Hellwig , Marek Szyprowski , Robin Murphy , Linux IOMMU , Khalid Aziz , "Maciej W . Rozycki" , Matt Wang , Miquel van Smoorenburg , Mark Salyzyn , linuxppc-dev , Linux-Arch , alpha , linux-m68k , Parisc List , Denis Efremov , Michael Ellerman , John Paul Adrian Glaubitz References: <20220617125750.728590-1-arnd@kernel.org> <20220617125750.728590-4-arnd@kernel.org> <6ba86afe-bf9f-1aca-7af1-d0d348d75ffc@gmail.com> <9289fd82-285c-035f-5355-4d70ce4f87b0@gmail.com> From: Michael Schmitz In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Arnd, On 29/06/22 09:50, Arnd Bergmann wrote: > On Tue, Jun 28, 2022 at 11:03 PM Michael Schmitz wrote: >> On 28/06/22 19:03, Geert Uytterhoeven wrote: >>>> The driver allocates bounce buffers using kmalloc if it hits an >>>> unaligned data buffer - can such buffers still even happen these days? >>> No idea. >> Hmmm - I think I'll stick a WARN_ONCE() in there so we know whether this >> code path is still being used. > kmalloc() guarantees alignment to the next power-of-two size or > KMALLOC_MIN_ALIGN, whichever is bigger. On m68k this means it > is cacheline aligned. And all SCSI buffers are allocated using kmalloc? No way at all for user space to pass unaligned data? (SCSI is a weird beast - I have used a SCSI DAT tape driver many many years ago, which broke all sorts of assumptions about transfer block sizes ... but that might actually have been in the v0.99 days, many rewrites of SCSI midlevel ago). Just being cautious, as getting any of this tested will be a stretch. Cheers,     Michael > > Arnd