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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7D888C4167B for ; Wed, 6 Dec 2023 16:23:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1379277AbjLFQX1 (ORCPT ); Wed, 6 Dec 2023 11:23:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44302 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1379155AbjLFQXZ (ORCPT ); Wed, 6 Dec 2023 11:23:25 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4E97C12F for ; Wed, 6 Dec 2023 08:23:32 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C4457C433C8; Wed, 6 Dec 2023 16:23:27 +0000 (UTC) Date: Wed, 6 Dec 2023 16:23:25 +0000 From: Catalin Marinas To: Jason Gunthorpe Cc: Lorenzo Pieralisi , Marc Zyngier , ankita@nvidia.com, Shameerali Kolothum Thodi , oliver.upton@linux.dev, suzuki.poulose@arm.com, yuzenghui@huawei.com, will@kernel.org, ardb@kernel.org, akpm@linux-foundation.org, gshan@redhat.com, aniketa@nvidia.com, cjia@nvidia.com, kwankhede@nvidia.com, targupta@nvidia.com, vsethi@nvidia.com, acurrid@nvidia.com, apopple@nvidia.com, jhubbard@nvidia.com, danw@nvidia.com, mochs@nvidia.com, kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 1/1] KVM: arm64: allow the VM to select DEVICE_* and NORMAL_NC for IO memory Message-ID: References: <20231205130517.GD2692119@nvidia.com> <20231205164318.GG2692119@nvidia.com> <20231205194822.GL2692119@nvidia.com> <20231206150556.GQ2692119@nvidia.com> <20231206153809.GS2692119@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231206153809.GS2692119@nvidia.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 06, 2023 at 11:38:09AM -0400, Jason Gunthorpe wrote: > On Wed, Dec 06, 2023 at 04:18:05PM +0100, Lorenzo Pieralisi wrote: > > On Wed, Dec 06, 2023 at 11:05:56AM -0400, Jason Gunthorpe wrote: > > > On Wed, Dec 06, 2023 at 02:49:02PM +0000, Catalin Marinas wrote: > > > > BTW, on those Mellanox devices that require different attributes within > > > > a BAR, do they have a problem with speculative reads causing > > > > side-effects? > > > > > > Yes. We definitely have had that problem in the past on older > > > devices. VFIO must map the BAR using pgprot_device/noncached() into > > > the VMM, no other choice is functionally OK. > > > > Were those BARs tagged as prefetchable or non-prefetchable ? I assume the > > latter but please let me know if I am guessing wrong. > > I don't know it was quite old HW. Probably. > > Just because a BAR is not marked as prefetchable doesn't mean that the > device can't use NORMAL_NC on subsets of it. What about the other way around - would we have a prefetchable BAR that has portions which are unprefetchable? -- Catalin