From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mp0 ([2001:41d0:2:4a6f::]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) by ms11 with LMTPS id 6IxjBIM7KV+9SQAA0tVLHw (envelope-from ) for ; Tue, 04 Aug 2020 10:42:11 +0000 Received: from aspmx1.migadu.com ([2001:41d0:2:4a6f::]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) by mp0 with LMTPS id AJI7AIM7KV9fZQAA1q6Kng (envelope-from ) for ; Tue, 04 Aug 2020 10:42:11 +0000 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by aspmx1.migadu.com (Postfix) with ESMTPS id 735F794005D for ; Tue, 4 Aug 2020 10:42:10 +0000 (UTC) Received: from localhost ([::1]:48472 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1k2uOV-0007Kz-AX for larch@yhetil.org; Tue, 04 Aug 2020 06:42:07 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:41136) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1k2uKY-0001K5-NG for guix-patches@gnu.org; Tue, 04 Aug 2020 06:38:02 -0400 Received: from debbugs.gnu.org ([209.51.188.43]:35404) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1k2uKY-0002NH-92 for guix-patches@gnu.org; Tue, 04 Aug 2020 06:38:02 -0400 Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1k2uKX-00047d-WF for guix-patches@gnu.org; Tue, 04 Aug 2020 06:38:02 -0400 X-Loop: help-debbugs@gnu.org Subject: [bug#42686] Update to linux-libre 5.7 Resent-From: Danny Milosavljevic Original-Sender: "Debbugs-submit" Resent-CC: guix-patches@gnu.org Resent-Date: Tue, 04 Aug 2020 10:38:01 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 42686 X-GNU-PR-Package: guix-patches X-GNU-PR-Keywords: To: Leo Famulari Cc: 42686@debbugs.gnu.org Received: via spool by 42686-submit@debbugs.gnu.org id=B42686.159653742515780 (code B ref 42686); Tue, 04 Aug 2020 10:38:01 +0000 Received: (at 42686) by debbugs.gnu.org; 4 Aug 2020 10:37:05 +0000 Received: from localhost ([127.0.0.1]:46950 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1k2uJd-00046S-CI for submit@debbugs.gnu.org; Tue, 04 Aug 2020 06:37:05 -0400 Received: from dd26836.kasserver.com ([85.13.145.193]:49900) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1k2uJa-000467-UW for 42686@debbugs.gnu.org; Tue, 04 Aug 2020 06:37:04 -0400 Received: from localhost (80-110-127-146.cgn.dynamic.surfer.at [80.110.127.146]) by dd26836.kasserver.com (Postfix) with ESMTPSA id 0DC0F336520B; Tue, 4 Aug 2020 12:37:01 +0200 (CEST) Date: Tue, 4 Aug 2020 12:36:57 +0200 From: Danny Milosavljevic Message-ID: <20200804123657.67daa48e@scratchpost.org> In-Reply-To: <20200802224356.GA4714@jasmine.lan> References: <20200802224356.GA4714@jasmine.lan> X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; x86_64-unknown-linux-gnu) MIME-Version: 1.0 Content-Type: multipart/signed; boundary="Sig_/G57lME_m7WTpCZ5iGEtRQwy"; protocol="application/pgp-signature"; micalg=pgp-sha512 X-Spam-Score: -0.7 (/) X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-Spam-Score: -1.7 (-) X-BeenThere: guix-patches@gnu.org List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: guix-patches-bounces+larch=yhetil.org@gnu.org Sender: "Guix-patches" X-Scanner: scn0 Authentication-Results: aspmx1.migadu.com; dkim=none; dmarc=none; spf=pass (aspmx1.migadu.com: domain of guix-patches-bounces@gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=guix-patches-bounces@gnu.org X-Spam-Score: -1.11 X-TUID: y9EefWmgOCRy --Sig_/G57lME_m7WTpCZ5iGEtRQwy Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Hi Leo, On Sun, 2 Aug 2020 18:43:56 -0400 Leo Famulari wrote: > * Enable the DMA-BUF userland memory heaps? This options creates per > heap chardevs in /dev/dma_heap/ which allows userspace to allocate > dma-bufs that can be shared between drivers. (DMABUF_HEAPS) >=20 > I don't really know what that means. DMA ("direct memory access") is a method to automatically have devices tran= sfer memory blocks to (and/or from) volatile memory without the involvement of t= he CPU. dma-bufs are buffers that can be used for DMA. These are distinct from reg= ular buffers because DMA is done without the involvement of the CPU, so setting = up a DMA buffer, telling the device the buffer location, and then freeing (or swapping out) the buffer would be very bad (the device wouldn't know that it is freed and would just continue using it, bypassing all the usual kernel access checks--because it doesn't use the CPU in the first place). A dma-buf heap is an allocator for dma-buf buffers and some limits where it can allocate. That is needed because peripheral chips have all kinds of weird limitations on where the dma-buf buffer can be in memory (for example some GPUs require the dma-buf buffers to be in the first 256 MiB of memory), so the allocator has to take into account that the later devices can actual= ly reach the buffers and give them a dma-buf buffer at some weird location, aliged like the device likes it and size-padded so the device doesn't scribble over something else while using potentially huge block transfers. A dma-buf userland memory heap is a device file in directory /dev/dma_heap/ which is connected to one specific dma-buf heap allocator in the kernel. A userspace program can then use a weird ioctl to request a dma-buf buffer, which then will be allocated. A file descriptor will be returned to the userspace program. This FD can be inherited by child processes etc--the usual. These dma-buf buffers are annoying in that you can't swap them out, free th= em and reallocate them later--or anything else you would do with normal memory. Also, when using them you need to use a memory fence in order to synchronize accesses between the CPU and the other devices that are using the buffer. That means allocating those dma-buf buffers without needing them is a great way to exhaust all RAM, with the kernel not having any recourse in reclaimi= ng them. So, require root. If the heap allocator that is used for that has a device-specific limit, that is much safer, though. The thing is mostly used by Android. --Sig_/G57lME_m7WTpCZ5iGEtRQwy Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEEds7GsXJ0tGXALbPZ5xo1VCwwuqUFAl8pOkkACgkQ5xo1VCww uqVx3Qf/TEKS5+TG14ryOB6Tt66E4SUg7/yyTnE+PK1GFo/M6bkS1s+sXGuL0z74 +PB16P+zlfFYcDyF4HDwrIFjk9t22foutfbIJkEdTq0osKdPIt/hbIqVLM5qrhdI n+EYdjMf/lYbPnNZVkJPdk73CUDTWXptU6aWyN2j39l3GJxcRUA58kWY34lF+jCc V0uRMeMVdzCNALZrcz9zY/Hb9gFQE2z4DKd8lVSltJs1aec3Qlu1eaIJC9g0O55f 45pVJffSPuyIgbuedxQch6UuIBkwndGO8xw4H9o9sqoc0F30jx2Hg+BfnAb/fa2z FEcjb51wHQiCp4R6ZdkHmHXnolHZ2g== =/j25 -----END PGP SIGNATURE----- --Sig_/G57lME_m7WTpCZ5iGEtRQwy--