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[209.132.180.67]) by mx.google.com with ESMTP id g141si905459oib.45.2020.02.27.02.57.07; Thu, 27 Feb 2020 02:57:18 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=FNNkRHSB; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728886AbgB0K4y (ORCPT + 99 others); Thu, 27 Feb 2020 05:56:54 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:56222 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728876AbgB0K4y (ORCPT ); Thu, 27 Feb 2020 05:56:54 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1582801013; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=DYpy6RJTXglkEu2oTovR+MB3265JeXuBkFoSO+vFOFs=; b=FNNkRHSBPyxwq5Ll7qEgjvrdTfohJOvFZxl9s1TlF2y2NRSrue2G+hs9JerYEHQq21DkIQ 2KRBVe2xdtRUEFY3/eWqA4ypxSE27TeOChxRM5v0j4Xfs4iHoVKs/xU+twW9X8PrBbHo0j XRKprR69Kno55mL3jpqR/kPFlZi9I4k= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-243-EQVjFHmoPeexcX8WUqiLWQ-1; Thu, 27 Feb 2020 05:56:49 -0500 X-MC-Unique: EQVjFHmoPeexcX8WUqiLWQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1E7E9107ACC7; Thu, 27 Feb 2020 10:56:45 +0000 (UTC) Received: from sirius.home.kraxel.org (ovpn-116-150.ams2.redhat.com [10.36.116.150]) by smtp.corp.redhat.com (Postfix) with ESMTP id 999838D540; Thu, 27 Feb 2020 10:56:44 +0000 (UTC) Received: by sirius.home.kraxel.org (Postfix, from userid 1000) id C6B561744A; Thu, 27 Feb 2020 11:56:43 +0100 (CET) Date: Thu, 27 Feb 2020 11:56:43 +0100 From: Gerd Hoffmann To: Thomas =?utf-8?Q?Hellstr=C3=B6m_=28VMware=29?= Cc: dri-devel@lists.freedesktop.org, Guillaume.Gardet@arm.com, David Airlie , open list , stable@vger.kernel.org, gurchetansingh@chromium.org, tzimmermann@suse.de Subject: Re: [PATCH v5 1/3] drm/shmem: add support for per object caching flags. Message-ID: <20200227105643.h4klc3ybhpwv2l3x@sirius.home.kraxel.org> References: <20200226154752.24328-1-kraxel@redhat.com> <20200226154752.24328-2-kraxel@redhat.com> <20200227075321.ki74hfjpnsqv2yx2@sirius.home.kraxel.org> <41ca197c-136a-75d8-b269-801db44d4cba@shipmail.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <41ca197c-136a-75d8-b269-801db44d4cba@shipmail.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, > I think it might be safe for some integrated graphics where the driver > maintainers can guarantee that it's safe on all particular processors used > with that driver, but then IMO it should be moved out to those drivers. > > Other drivers needing write-combine shouldn't really use shmem. > > So again, to fix the regression, could we revert 0be895893607f ("drm/shmem: > switch shmem helper to &drm_gem_object_funcs.mmap") or does that have other > implications? This patch isn't a regression. The old code path has the pgprot_writecombine() call in drm_gem_mmap_obj(), so the behavior is the same before and afterwards. But with the patch in place we can easily have shmem helpers do their own thing instead of depending on whatever drm_gem_mmap_obj() is doing. Just using cached mappings unconditionally would be perfectly fine for virtio-gpu. Not sure about the other users though. I'd like to fix the virtio-gpu regression (coming from ttm -> shmem switch) asap, and I don't feel like changing the behavior for other drivers in 5.6-rc is a good idea. So I'd like to push patches 1+2 to -fixes and sort everything else later in -next. OK? cheers, Gerd