From: David Laight <David.Laight@ACULAB.COM> To: 'Ard Biesheuvel' <ard.biesheuvel@linaro.org>, Ramana Radhakrishnan <ramana.gcc@googlemail.com> Cc: Florian Weimer <fweimer@redhat.com>, Thomas Petazzoni <thomas.petazzoni@free-electrons.com>, GNU C Library <libc-alpha@sourceware.org>, Andrew Pinski <pinskia@gmail.com>, "Catalin Marinas" <catalin.marinas@arm.com>, Will Deacon <will.deacon@arm.com>, "Russell King" <linux@armlinux.org.uk>, LKML <linux-kernel@vger.kernel.org>, "Mikulas Patocka" <mpatocka@redhat.com>, linux-arm-kernel <linux-arm-kernel@lists.infradead.org> Subject: RE: framebuffer corruption due to overlapping stp instructions on arm64 Date: Fri, 3 Aug 2018 11:24:28 +0000 [thread overview] Message-ID: <f696ebe8605840e3bb04bb78b60a6cfa@AcuMS.aculab.com> (raw) In-Reply-To: <CAKv+Gu97QvwoLLK_zueiA_gjg_4Q5cqU4YVUyHUVFFfffdyJaw@mail.gmail.com> From: Ard Biesheuvel > Sent: 03 August 2018 10:30 ... > The discussion about whether memcpy() should rely on unaligned > accesses, and whether you should use it on device memory is orthogonal > to that, and not the heart of the matter IMO Even on x86 using memcpy() on PCIe memory (maybe mmap()ed into userspace) isn't a good idea. In the kernel memcpy_to/fromio() ought to be a better choice but that is just an alternate name for memcpy(). The problem on x86 is that memcpy() is likely to be implemented as 'rep movsb' on modern cpu - relying on the cpu hardware to perform cache-line sized transfers (etc). Unfortunately on uncached locations it has to revert to byte copies. So PCIe transfers (especially reads) are very slow. The transfers need to use the largest size register available. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
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From: David.Laight@ACULAB.COM (David Laight) To: linux-arm-kernel@lists.infradead.org Subject: framebuffer corruption due to overlapping stp instructions on arm64 Date: Fri, 3 Aug 2018 11:24:28 +0000 [thread overview] Message-ID: <f696ebe8605840e3bb04bb78b60a6cfa@AcuMS.aculab.com> (raw) In-Reply-To: <CAKv+Gu97QvwoLLK_zueiA_gjg_4Q5cqU4YVUyHUVFFfffdyJaw@mail.gmail.com> From: Ard Biesheuvel > Sent: 03 August 2018 10:30 ... > The discussion about whether memcpy() should rely on unaligned > accesses, and whether you should use it on device memory is orthogonal > to that, and not the heart of the matter IMO Even on x86 using memcpy() on PCIe memory (maybe mmap()ed into userspace) isn't a good idea. In the kernel memcpy_to/fromio() ought to be a better choice but that is just an alternate name for memcpy(). The problem on x86 is that memcpy() is likely to be implemented as 'rep movsb' on modern cpu - relying on the cpu hardware to perform cache-line sized transfers (etc). Unfortunately on uncached locations it has to revert to byte copies. So PCIe transfers (especially reads) are very slow. The transfers need to use the largest size register available. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2018-08-03 11:22 UTC|newest] Thread overview: 238+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-08-02 19:31 framebuffer corruption due to overlapping stp instructions on arm64 Mikulas Patocka 2018-08-02 19:31 ` Mikulas Patocka [not found] ` <CAHCPf3tFGqkYEcWNN4LaWThw_rVqT316pzLv6T7RfxwO-eZ0EA@mail.gmail.com> 2018-08-03 6:35 ` Mikulas Patocka 2018-08-03 6:35 ` Mikulas Patocka 2018-08-03 7:16 ` Ard Biesheuvel 2018-08-03 7:16 ` Ard Biesheuvel 2018-08-03 9:41 ` Will Deacon 2018-08-03 9:41 ` Will Deacon 2018-08-03 17:09 ` Mikulas Patocka 2018-08-03 17:09 ` Mikulas Patocka 2018-08-03 17:09 ` Mikulas Patocka 2018-08-03 17:32 ` Sinan Kaya 2018-08-03 17:32 ` Sinan Kaya 2018-08-03 17:32 ` Sinan Kaya 2018-08-03 17:33 ` Ard Biesheuvel 2018-08-03 17:33 ` Ard Biesheuvel 2018-08-03 17:33 ` Ard Biesheuvel 2018-08-03 18:25 ` Mikulas Patocka 2018-08-03 18:25 ` Mikulas Patocka 2018-08-03 18:25 ` Mikulas Patocka 2018-08-03 20:44 ` Matt Sealey 2018-08-03 20:44 ` Matt Sealey 2018-08-03 20:44 ` Matt Sealey 2018-08-03 21:20 ` Ard Biesheuvel 2018-08-03 21:20 ` Ard Biesheuvel 2018-08-03 21:20 ` Ard Biesheuvel 2018-08-06 10:25 ` Mikulas Patocka 2018-08-06 10:25 ` Mikulas Patocka 2018-08-06 10:25 ` Mikulas Patocka 2018-08-06 12:42 ` Robin Murphy 2018-08-06 12:42 ` Robin Murphy 2018-08-06 12:42 ` Robin Murphy 2018-08-06 12:53 ` Ard Biesheuvel 2018-08-06 12:53 ` Ard Biesheuvel 2018-08-06 12:53 ` Ard Biesheuvel 2018-08-06 13:41 ` Marcin Wojtas 2018-08-06 13:41 ` Marcin Wojtas 2018-08-06 13:41 ` Marcin Wojtas 2018-08-06 13:48 ` Ard Biesheuvel 2018-08-06 13:48 ` Ard Biesheuvel 2018-08-06 13:48 ` Ard Biesheuvel 2018-08-06 14:07 ` Marcin Wojtas 2018-08-06 14:07 ` Marcin Wojtas 2018-08-06 14:07 ` Marcin Wojtas 2018-08-06 14:13 ` Mikulas Patocka 2018-08-06 14:13 ` Mikulas Patocka 2018-08-06 14:13 ` Mikulas Patocka 2018-08-06 15:47 ` Ard Biesheuvel 2018-08-06 15:47 ` Ard Biesheuvel 2018-08-06 15:47 ` Ard Biesheuvel 2018-08-06 17:09 ` Mikulas Patocka 2018-08-06 17:09 ` Mikulas Patocka 2018-08-06 17:09 ` Mikulas Patocka 2018-08-06 17:21 ` Ard Biesheuvel 2018-08-06 17:21 ` Ard Biesheuvel 2018-08-06 17:21 ` Ard Biesheuvel 2018-08-06 19:54 ` Mikulas Patocka 2018-08-06 19:54 ` Mikulas Patocka 2018-08-06 19:54 ` Mikulas Patocka 2018-08-06 20:11 ` Ard Biesheuvel 2018-08-06 20:11 ` Ard Biesheuvel 2018-08-06 20:11 ` Ard Biesheuvel 2018-08-06 20:31 ` Mikulas Patocka 2018-08-06 20:31 ` Mikulas Patocka 2018-08-06 20:31 ` Mikulas Patocka 2018-08-07 16:40 ` Marcin Wojtas 2018-08-07 16:40 ` Marcin Wojtas 2018-08-07 16:40 ` Marcin Wojtas 2018-08-07 17:39 ` Mikulas Patocka 2018-08-07 17:39 ` Mikulas Patocka 2018-08-07 17:39 ` Mikulas Patocka 2018-08-07 18:07 ` Ard Biesheuvel 2018-08-07 18:07 ` Ard Biesheuvel 2018-08-07 18:07 ` Ard Biesheuvel 2018-08-07 18:17 ` Mikulas Patocka 2018-08-07 18:17 ` Mikulas Patocka 2018-08-07 18:17 ` Mikulas Patocka [not found] ` <CAPv3WKcKoEe=Qysp6Oac2C=G9bUhUQf1twSRCY+_qJ6XEC-iag@mail.gmail.com> 2018-08-08 14:10 ` Mikulas Patocka 2018-08-08 14:10 ` Mikulas Patocka 2018-08-08 14:10 ` Mikulas Patocka 2018-08-06 17:13 ` Catalin Marinas 2018-08-06 17:13 ` Catalin Marinas 2018-08-06 17:13 ` Catalin Marinas 2018-08-06 17:19 ` Mikulas Patocka 2018-08-06 17:19 ` Mikulas Patocka 2018-08-06 17:19 ` Mikulas Patocka 2018-08-08 18:31 ` Mikulas Patocka 2018-08-08 18:31 ` Mikulas Patocka 2018-08-08 18:31 ` Mikulas Patocka 2018-08-04 13:29 ` Mikulas Patocka 2018-08-04 13:29 ` Mikulas Patocka 2018-08-04 13:29 ` Mikulas Patocka 2018-08-08 12:16 ` Catalin Marinas 2018-08-08 12:16 ` Catalin Marinas 2018-08-08 12:16 ` Catalin Marinas 2018-08-08 13:02 ` David Laight 2018-08-08 13:02 ` David Laight 2018-08-08 13:02 ` David Laight 2018-08-08 13:46 ` Mikulas Patocka 2018-08-08 13:46 ` Mikulas Patocka 2018-08-08 13:46 ` Mikulas Patocka 2018-08-08 14:26 ` David Laight 2018-08-08 14:26 ` David Laight 2018-08-08 14:26 ` David Laight 2018-08-08 14:50 ` Catalin Marinas 2018-08-08 14:50 ` Catalin Marinas 2018-08-08 14:50 ` Catalin Marinas 2018-08-08 16:21 ` Mikulas Patocka 2018-08-08 16:21 ` Mikulas Patocka 2018-08-08 16:21 ` Mikulas Patocka 2018-08-08 16:31 ` Arnd Bergmann 2018-08-08 16:31 ` Arnd Bergmann 2018-08-08 16:31 ` Arnd Bergmann 2018-08-08 16:43 ` David Laight 2018-08-08 16:43 ` David Laight 2018-08-08 16:43 ` David Laight 2018-08-08 18:56 ` Mikulas Patocka 2018-08-08 18:56 ` Mikulas Patocka 2018-08-08 18:56 ` Mikulas Patocka 2018-08-08 18:37 ` Mikulas Patocka 2018-08-08 18:37 ` Mikulas Patocka 2018-08-08 18:37 ` Mikulas Patocka 2018-08-08 11:39 ` Catalin Marinas 2018-08-08 11:39 ` Catalin Marinas 2018-08-08 11:39 ` Catalin Marinas 2018-08-08 14:12 ` Mikulas Patocka 2018-08-08 14:12 ` Mikulas Patocka 2018-08-08 14:12 ` Mikulas Patocka 2018-08-08 14:28 ` Catalin Marinas 2018-08-08 14:28 ` Catalin Marinas 2018-08-08 14:28 ` Catalin Marinas 2018-08-08 18:40 ` Mikulas Patocka 2018-08-08 18:40 ` Mikulas Patocka 2018-08-08 18:40 ` Mikulas Patocka 2018-08-08 15:01 ` Richard Earnshaw (lists) 2018-08-08 15:01 ` Richard Earnshaw (lists) 2018-08-08 15:01 ` Richard Earnshaw (lists) 2018-08-08 15:14 ` Catalin Marinas 2018-08-08 15:14 ` Catalin Marinas 2018-08-08 15:14 ` Catalin Marinas 2018-08-08 16:01 ` Arnd Bergmann 2018-08-08 16:01 ` Arnd Bergmann 2018-08-08 16:01 ` Arnd Bergmann 2018-08-08 18:25 ` Mikulas Patocka 2018-08-08 18:25 ` Mikulas Patocka 2018-08-08 18:25 ` Mikulas Patocka 2018-08-08 21:51 ` Arnd Bergmann 2018-08-08 21:51 ` Arnd Bergmann 2018-08-08 21:51 ` Arnd Bergmann 2018-08-09 15:29 ` Arnd Bergmann 2018-08-09 15:29 ` Arnd Bergmann 2018-08-09 15:29 ` Arnd Bergmann 2018-08-03 7:11 ` Andrew Pinski 2018-08-03 7:11 ` Andrew Pinski 2018-08-03 7:53 ` Florian Weimer 2018-08-03 7:53 ` Florian Weimer 2018-08-03 9:12 ` Szabolcs Nagy 2018-08-03 9:12 ` Szabolcs Nagy 2018-08-03 9:15 ` Ramana Radhakrishnan 2018-08-03 9:15 ` Ramana Radhakrishnan 2018-08-03 9:29 ` Ard Biesheuvel 2018-08-03 9:29 ` Ard Biesheuvel 2018-08-03 9:37 ` Ramana Radhakrishnan 2018-08-03 9:37 ` Ramana Radhakrishnan 2018-08-03 9:42 ` Richard Earnshaw (lists) 2018-08-03 9:42 ` Richard Earnshaw (lists) 2018-08-04 0:58 ` Mikulas Patocka 2018-08-04 0:58 ` Mikulas Patocka 2018-08-04 1:13 ` Andrew Pinski 2018-08-04 1:13 ` Andrew Pinski 2018-08-04 11:04 ` Mikulas Patocka 2018-08-04 11:04 ` Mikulas Patocka 2018-08-05 18:33 ` Florian Weimer 2018-08-05 18:33 ` Florian Weimer 2018-08-06 8:02 ` Mikulas Patocka 2018-08-06 8:02 ` Mikulas Patocka 2018-08-06 8:10 ` Ard Biesheuvel 2018-08-06 8:10 ` Ard Biesheuvel 2018-08-06 10:31 ` Mikulas Patocka 2018-08-06 10:31 ` Mikulas Patocka 2018-08-06 10:37 ` Ard Biesheuvel 2018-08-06 10:37 ` Ard Biesheuvel 2018-08-06 10:42 ` Mikulas Patocka 2018-08-06 10:42 ` Mikulas Patocka 2018-08-06 10:48 ` Ard Biesheuvel 2018-08-06 10:48 ` Ard Biesheuvel 2018-08-06 12:09 ` Mikulas Patocka 2018-08-06 12:09 ` Mikulas Patocka 2018-08-06 12:19 ` Ard Biesheuvel 2018-08-06 12:19 ` Ard Biesheuvel 2018-08-06 12:22 ` Ard Biesheuvel 2018-08-06 12:22 ` Ard Biesheuvel 2018-08-07 14:14 ` Mikulas Patocka 2018-08-07 14:14 ` Mikulas Patocka 2018-08-07 14:40 ` Ard Biesheuvel 2018-08-07 14:40 ` Ard Biesheuvel 2018-08-08 19:15 ` Mikulas Patocka 2018-08-08 19:15 ` Mikulas Patocka 2018-08-06 11:19 ` Siddhesh Poyarekar 2018-08-06 11:19 ` Siddhesh Poyarekar 2018-08-06 11:29 ` Ard Biesheuvel 2018-08-06 11:29 ` Ard Biesheuvel 2018-08-06 14:26 ` Tulio Magno Quites Machado Filho 2018-08-06 14:26 ` Tulio Magno Quites Machado Filho 2018-08-05 21:51 ` Pavel Machek 2018-08-05 21:51 ` Pavel Machek 2018-08-06 14:30 ` Mikulas Patocka 2018-08-06 14:30 ` Mikulas Patocka 2018-08-03 11:24 ` David Laight [this message] 2018-08-03 11:24 ` David Laight 2018-08-03 12:04 ` Mikulas Patocka 2018-08-03 12:04 ` Mikulas Patocka 2018-08-03 13:04 ` David Laight 2018-08-03 13:04 ` David Laight 2018-08-05 14:36 ` Mikulas Patocka 2018-08-05 14:36 ` Mikulas Patocka 2018-08-06 10:18 ` David Laight 2018-08-06 10:18 ` David Laight 2018-08-07 14:07 ` Mikulas Patocka 2018-08-07 14:07 ` Mikulas Patocka 2018-08-07 14:33 ` David Laight 2018-08-07 14:33 ` David Laight 2018-08-08 14:21 ` Mikulas Patocka 2018-08-08 14:21 ` Mikulas Patocka 2018-08-03 13:20 ` Mikulas Patocka 2018-08-03 13:20 ` Mikulas Patocka 2018-08-03 13:31 ` Mikulas Patocka 2018-08-03 13:31 ` Mikulas Patocka 2018-08-03 14:17 ` Richard Earnshaw (lists) 2018-08-03 14:17 ` Richard Earnshaw (lists) 2018-08-05 21:36 ` Pavel Machek 2018-08-05 21:36 ` Pavel Machek 2018-08-06 8:04 ` Ramana Radhakrishnan 2018-08-06 8:04 ` Ramana Radhakrishnan 2018-08-06 8:44 ` Pavel Machek 2018-08-06 8:44 ` Pavel Machek 2018-08-06 9:11 ` Ard Biesheuvel 2018-08-06 9:11 ` Ard Biesheuvel
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