From: Catalin Marinas <catalin.marinas@arm.com>
To: Arnd Bergmann <arnd@kernel.org>
Cc: linux-kernel@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
Vineet Gupta <vgupta@kernel.org>,
Russell King <linux@armlinux.org.uk>,
Neil Armstrong <neil.armstrong@linaro.org>,
Linus Walleij <linus.walleij@linaro.org>,
Will Deacon <will@kernel.org>, Guo Ren <guoren@kernel.org>,
Brian Cain <bcain@quicinc.com>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Michal Simek <monstr@monstr.eu>,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
Dinh Nguyen <dinguyen@kernel.org>,
Stafford Horne <shorne@gmail.com>, Helge Deller <deller@gmx.de>,
Michael Ellerman <mpe@ellerman.id.au>,
Christophe Leroy <christophe.leroy@csgroup.eu>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Rich Felker <dalias@libc.org>,
John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
"David S. Miller" <davem@davemloft.net>,
Max Filippov <jcmvbkbc@gmail.com>, Christoph Hellwig <hch@lst.de>,
Robin Murphy <robin.murphy@arm.com>,
Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>,
Conor Dooley <conor.dooley@microchip.com>,
linux-snps-arc@lists.infradead.org,
linux-arm-kernel@lists.infradead.org, linux-oxnas@groups.io,
linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org,
linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org,
linux-openrisc@vger.kernel.org, linux-parisc@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org,
linux-sh@vger.kernel.org, sparclinux@vger.kernel.org,
linux-xtensa@linux-xtensa.org
Subject: Re: [PATCH 00/21] dma-mapping: unify support for cache flushes
Date: Fri, 31 Mar 2023 17:53:45 +0100 [thread overview]
Message-ID: <ZCcQGX/i8xBPiG7T@arm.com> (raw)
In-Reply-To: <20230327121317.4081816-1-arnd@kernel.org>
On Mon, Mar 27, 2023 at 02:12:56PM +0200, Arnd Bergmann wrote:
> Another difference that I do not address here is what cache invalidation
> does for partical cache lines. On arm32, arm64 and powerpc, a partial
> cache line always gets written back before invalidation in order to
> ensure that data before or after the buffer is not discarded. On all
> other architectures, the assumption is cache lines are never shared
> between DMA buffer and data that is accessed by the CPU.
I don't think sharing the DMA buffer with other data is safe even with
this clean+invalidate on the unaligned cache. Mapping the DMA buffer as
FROM_DEVICE or BIDIRECTIONAL can cause the shared cache line to be
evicted and override the device written data. This sharing only works if
the CPU guarantees not to dirty the corresponding cache line.
I'm fine with removing this partial cache line hack from arm64 as it's
not safe anyway. We'll see if any driver stops working. If there's some
benign sharing (I wouldn't trust it), the cache cleaning prior to
mapping and invalidate on unmap would not lose any data.
--
Catalin
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next prev parent reply other threads:[~2023-03-31 16:54 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-27 12:12 [PATCH 00/21] dma-mapping: unify support for cache flushes Arnd Bergmann
2023-03-27 12:12 ` [PATCH 01/21] openrisc: dma-mapping: flush bidirectional mappings Arnd Bergmann
2023-03-27 12:12 ` [PATCH 02/21] xtensa: dma-mapping: use normal cache invalidation rules Arnd Bergmann
2023-03-27 15:42 ` Max Filippov
2023-03-27 12:12 ` [PATCH 03/21] sparc32: flush caches in dma_sync_*for_device Arnd Bergmann
2023-03-27 12:13 ` [PATCH 04/21] microblaze: dma-mapping: skip extra DMA flushes Arnd Bergmann
2023-03-27 12:13 ` [PATCH 05/21] powerpc: dma-mapping: split out cache operation logic Arnd Bergmann
2023-03-27 12:13 ` [PATCH 06/21] powerpc: dma-mapping: minimize for_cpu flushing Arnd Bergmann
2023-03-27 12:56 ` Christophe Leroy
2023-03-27 13:02 ` Arnd Bergmann
2023-03-27 12:13 ` [PATCH 07/21] powerpc: dma-mapping: always clean cache in _for_device() op Arnd Bergmann
2023-03-27 12:13 ` [PATCH 08/21] riscv: dma-mapping: only invalidate after DMA, not flush Arnd Bergmann
2023-03-29 20:48 ` Conor Dooley
2023-03-30 7:10 ` Arnd Bergmann
2023-03-29 21:51 ` Jessica Clarke
2023-03-30 12:59 ` Lad, Prabhakar
2023-04-19 14:22 ` Palmer Dabbelt
2023-03-27 12:13 ` [PATCH 09/21] riscv: dma-mapping: skip invalidation before bidirectional DMA Arnd Bergmann
2023-03-29 20:16 ` Conor Dooley
2023-03-30 13:26 ` Lad, Prabhakar
2023-04-19 14:22 ` Palmer Dabbelt
2023-05-05 5:47 ` Guo Ren
2023-05-05 13:18 ` Arnd Bergmann
2023-05-06 7:25 ` Guo Ren
2023-05-06 7:53 ` Arnd Bergmann
2023-03-27 12:13 ` [PATCH 10/21] csky: dma-mapping: skip invalidating before DMA from device Arnd Bergmann
2023-03-27 13:37 ` Guo Ren
2023-03-27 12:13 ` [PATCH 11/21] mips: dma-mapping: skip invalidating before bidirectional DMA Arnd Bergmann
2023-03-27 12:13 ` [PATCH 12/21] mips: dma-mapping: split out cache operation logic Arnd Bergmann
2023-03-27 12:13 ` [PATCH 13/21] arc: dma-mapping: skip invalidating before bidirectional DMA Arnd Bergmann
2023-04-02 6:52 ` Vineet Gupta
2023-04-04 8:27 ` Shahab Vahedi
2023-04-06 9:01 ` Shahab Vahedi
2023-03-27 12:13 ` [PATCH 14/21] parisc: dma-mapping: use regular flush/invalidate ops Arnd Bergmann
2023-03-27 12:13 ` [PATCH 15/21] ARM: dma-mapping: always invalidate WT caches before DMA Arnd Bergmann
2023-03-31 9:01 ` Linus Walleij
2023-03-31 9:07 ` Russell King (Oracle)
2023-03-31 9:35 ` Russell King (Oracle)
2023-03-31 10:38 ` Arnd Bergmann
2023-03-31 11:01 ` David Laight
2023-03-31 11:08 ` Russell King (Oracle)
2023-03-31 12:32 ` Arnd Bergmann
2023-03-27 12:13 ` [PATCH 16/21] ARM: dma-mapping: bring back dmac_{clean,inv}_range Arnd Bergmann
2023-03-27 13:10 ` Russell King (Oracle)
2023-03-27 12:13 ` [PATCH 17/21] ARM: dma-mapping: use arch_sync_dma_for_{device,cpu}() internally Arnd Bergmann
2023-03-31 9:10 ` Linus Walleij
2023-03-31 12:48 ` Arnd Bergmann
2023-03-27 12:13 ` [PATCH 18/21] ARM: drop SMP support for ARM11MPCore Arnd Bergmann
2023-03-30 7:48 ` Neil Armstrong
2023-03-30 10:03 ` Arnd Bergmann
2023-03-30 16:40 ` Neil Armstrong
2023-03-30 8:12 ` Linus Walleij
2023-03-30 11:51 ` Ard Biesheuvel
2023-03-31 17:09 ` Catalin Marinas
2023-03-27 12:13 ` [PATCH 19/21] ARM: dma-mapping: use generic form of arch_sync_dma_* helpers Arnd Bergmann
2023-03-27 12:13 ` [PATCH 20/21] ARM: dma-mapping: split out arch_dma_mark_clean() helper Arnd Bergmann
2023-03-27 12:48 ` Robin Murphy
2023-03-31 14:00 ` Arnd Bergmann
2023-03-31 15:12 ` Robin Murphy
2023-03-31 17:20 ` Arnd Bergmann
2023-03-27 15:01 ` Russell King (Oracle)
2023-03-31 14:06 ` Arnd Bergmann
2023-03-31 15:54 ` Russell King (Oracle)
2023-07-03 7:54 ` Geert Uytterhoeven
2023-07-06 14:11 ` Christoph Hellwig
2023-03-27 12:13 ` [PATCH 21/21] dma-mapping: replace custom code with generic implementation Arnd Bergmann
2023-03-27 22:25 ` Christoph Hellwig
2023-03-31 13:04 ` Arnd Bergmann
2023-03-30 14:06 ` Lad, Prabhakar
2023-04-13 12:13 ` Biju Das
2023-04-13 12:51 ` Arnd Bergmann
2023-06-27 16:52 ` Geert Uytterhoeven
2023-03-31 16:53 ` Catalin Marinas [this message]
2023-03-31 20:27 ` [PATCH 00/21] dma-mapping: unify support for cache flushes Arnd Bergmann
2023-05-25 7:46 ` Lad, Prabhakar
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