From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_NONE,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7B0FFC433E2 for ; Tue, 8 Sep 2020 11:38:48 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 39B8721532 for ; Tue, 8 Sep 2020 11:38:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="NAhOoKpE"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=ffwll.ch header.i=@ffwll.ch header.b="TRI4o8zL" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 39B8721532 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ffwll.ch Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=tQBqkURimGVxloFlx2fPzG/O4irX4ItwdSpdxQwZIto=; b=NAhOoKpENCGy9uvzf5oLRfK+c UkyxTjt1rPh1BvO9U8IWRSwBc7xz6D+a9O0renYbB+qFhyTp0IbqvTvY3jFZW33xJc8RgdqShA7wH vvhwNOYYdF+YVGvR0eHQoqxaA1PX87VBgEh0CeWMw5P54MPljqmgxqK0cpPECoBBo9u91mvWWTyFe ajK3uDm1zbX19TnnYCdjUFmljakgiSwsxc84JT9niG3GfCGkkGS2MuJYDuOxSpRYgIFtHodsoUS6p ykK70jSpLLfJCGaksltk3tELdudsmRjHIDV8WsWV0P3Xor4ss3mFBCSwf+XxDr6M9hQab7AE85vu0 zInAHtKaw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kFbw7-000518-RZ; Tue, 08 Sep 2020 11:37:19 +0000 Received: from mail-wr1-x444.google.com ([2a00:1450:4864:20::444]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kFbw4-0004yv-E8 for linux-arm-kernel@lists.infradead.org; Tue, 08 Sep 2020 11:37:17 +0000 Received: by mail-wr1-x444.google.com with SMTP id t10so18791151wrv.1 for ; Tue, 08 Sep 2020 04:37:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=date:from:to:cc:subject:message-id:mail-followup-to:references :mime-version:content-disposition:in-reply-to; bh=I/sh0hf7RWpKTkHRG2sXo6X29i3mK1fyatkLVFjwPyY=; b=TRI4o8zL814YHGA/D/zYMJIAaCIYqFZ0mIpUDMLZUZN87cVGkWukeoAQibFqRSdTi0 6pbezBxBfFFSAjRUKWB8QJP5CHgs93NHYtFiS1nIDp648nb0kIv2ZVQ/RTs1fTwlNaec GPg0wCc5jkN3j+ma2gtmxo4nY/EYhDvIrUWKQ= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id :mail-followup-to:references:mime-version:content-disposition :in-reply-to; bh=I/sh0hf7RWpKTkHRG2sXo6X29i3mK1fyatkLVFjwPyY=; b=pcXkOf055pT0n5NQBC9md3g+awb8VchXOYLuCa+aClAIFsApHplgBxPCdX8UMt2X0m 7S1IuO8u+gBu/QLUfkEqHMA2X2IMRjsB7hnjLiDOBGnhS43PUbVrfrSFoRnW9JrrZPjD n0I9Fd0Vs8MBRlfIHL6T9UfPffnGBWrg28pWy0CyiIVwIVOMs1twPzA4ggQY2NyVJJLu Qd8hysdpa0ZIWxd0wnsTkI7TH/UollBDL3Mm8wkOWsgp0EpFn/H9KBWdtYV2MLprP2Xa uiAXLGsuZoCo/OHKlcH8QIfp1E5LeP7p9e/ZwYi3Vl+n2qbxSMWvv01zlLvdhnK/dcGf qOMA== X-Gm-Message-State: AOAM531dYDwVWaoBbUd6Wr94BbIlbbQnZM68P+RlAmqQ7zERPIRovbvh U7wGFQGCDn9IZRYXxIqcH/HM/Q== X-Google-Smtp-Source: ABdhPJyF2qwliIvI/LNW3ilYwO975TKwRXyUs29RK60LvcJNYZwaiKnp5x/7ZaLEGFTKwLjPhYZ/og== X-Received: by 2002:adf:fd01:: with SMTP id e1mr24749831wrr.44.1599565035147; Tue, 08 Sep 2020 04:37:15 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id e18sm39103291wra.36.2020.09.08.04.37.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Sep 2020 04:37:14 -0700 (PDT) Date: Tue, 8 Sep 2020 13:37:12 +0200 From: Daniel Vetter To: Gerd Hoffmann Subject: Re: [PATCH v4 1/1] drm: allow limiting the scatter list size. Message-ID: <20200908113712.GL2352366@phenom.ffwll.local> Mail-Followup-To: Gerd Hoffmann , dri-devel , Christian =?iso-8859-1?Q?K=F6nig?= , Alex Deucher , David Airlie , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Lucas Stach , Russell King , Christian Gmeiner , Rob Clark , Sean Paul , Ben Skeggs , Sandy Huang , Heiko =?iso-8859-1?Q?St=FCbner?= , Thierry Reding , Jonathan Hunter , Oleksandr Andrushchenko , "open list:RADEON and AMDGPU DRM DRIVERS" , open list , "moderated list:DRM DRIVERS FOR VIVANTE GPU IP" , "open list:DRM DRIVER FOR MSM ADRENO GPU" , "open list:DRM DRIVER FOR MSM ADRENO GPU" , "open list:DRM DRIVER FOR NVIDIA GEFORCE/QUADRO GPUS" , "moderated list:ARM/Rockchip SoC support" , "open list:ARM/Rockchip SoC support" , "open list:DRM DRIVERS FOR NVIDIA TEGRA" , "moderated list:DRM DRIVERS FOR XEN" References: <20200907112425.15610-1-kraxel@redhat.com> <20200907112425.15610-2-kraxel@redhat.com> <20200908054858.um34wojjv6uhi7d3@sirius.home.kraxel.org> <20200908085544.GI2352366@phenom.ffwll.local> <20200908100253.b22sff23737l77bo@sirius.home.kraxel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200908100253.b22sff23737l77bo@sirius.home.kraxel.org> X-Operating-System: Linux phenom 5.7.0-1-amd64 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200908_073716_569998_F6991F83 X-CRM114-Status: GOOD ( 23.94 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Heiko =?iso-8859-1?Q?St=FCbner?= , David Airlie , "open list:DRM DRIVER FOR NVIDIA GEFORCE/QUADRO GPUS" , dri-devel , Sandy Huang , Thierry Reding , Oleksandr Andrushchenko , "open list:RADEON and AMDGPU DRM DRIVERS" , Jonathan Hunter , "open list:ARM/Rockchip SoC support" , Ben Skeggs , Russell King , "moderated list:DRM DRIVERS FOR XEN" , "open list:DRM DRIVER FOR MSM ADRENO GPU" , Maarten Lankhorst , "moderated list:DRM DRIVERS FOR VIVANTE GPU IP" , Maxime Ripard , Christian Gmeiner , "open list:DRM DRIVERS FOR NVIDIA TEGRA" , Sean Paul , "moderated list:ARM/Rockchip SoC support" , open list , Rob Clark , Thomas Zimmermann , Alex Deucher , "open list:DRM DRIVER FOR MSM ADRENO GPU" , Christian =?iso-8859-1?Q?K=F6nig?= , Lucas Stach Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Sep 08, 2020 at 12:02:53PM +0200, Gerd Hoffmann wrote: > > > > The comments I've found suggest very much not ... Or is that all very > > > > old stuff only that no one cares about anymore? > > > > > > I think these days it is possible to override dma_ops per device, which > > > in turn allows virtio to deal with the quirks without the rest of the > > > kernel knowing about these details. > > > > > > I also think virtio-gpu can drop the virtio_has_dma_quirk() checks, just > > > use the dma api path unconditionally and depend on virtio core having > > > setup dma_ops in a way that it JustWorks[tm]. I'll look into that next. > > > > The comment above vring_use_dma_api() suggests that this has not yet > > happened, that's why I'm asking. > > Hmm, wading through the code, seems it indeed happen yet, even though my > testing didn't show any issues. Probably pure luck because devices and > cpus have the same memory view on x86. Guess I need to try this on > ppc64 to see it actually failing ... > > So dropping the virtio_has_dma_quirk() checks isn't going to fly. > > Using dma_max_mapping_size() should be fine though. It might use a > lower limit than needed for virtio, but it should not break things. Makes sense. On this patch here: Reviewed-by: Daniel Vetter And I guess would be good if virtio pushes a bit more towards using the dma api abstraction fully so we can get rid of these hacks. Virtio feels like a driver that really should be using dma-api and not dig around behind it because "it' makes stuff 0.5% faster" or so, since being virtualized it's already not the king of speed anyway :-) Cheers, Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel