From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7F5DC675A1; Tue, 5 Dec 2023 16:24:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7D01CC433C8; Tue, 5 Dec 2023 16:24:25 +0000 (UTC) Date: Tue, 5 Dec 2023 16:24:22 +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: <20231205033015.10044-1-ankita@nvidia.com> <86fs0hatt3.wl-maz@kernel.org> <20231205130517.GD2692119@nvidia.com> <20231205144417.GE2692119@nvidia.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231205144417.GE2692119@nvidia.com> On Tue, Dec 05, 2023 at 10:44:17AM -0400, Jason Gunthorpe wrote: > On Tue, Dec 05, 2023 at 03:37:13PM +0100, Lorenzo Pieralisi wrote: > > On Tue, Dec 05, 2023 at 09:05:17AM -0400, Jason Gunthorpe wrote: > > > On Tue, Dec 05, 2023 at 11:40:47AM +0000, Catalin Marinas wrote: > > > > > - Will had unanswered questions in another part of the thread: > > > > > > > > > > https://lore.kernel.org/all/20231013092954.GB13524@willie-the-truck/ > > > > > > > > > > Can someone please help concluding it? > > > > > > > > Is this about reclaiming the device? I think we concluded that we can't > > > > generalise this beyond PCIe, though not sure there was any formal > > > > statement to that thread. The other point Will had was around stating > > > > in the commit message why we only relax this to Normal NC. I haven't > > > > checked the commit message yet, it needs careful reading ;). > > > > > > Not quite, we said reclaiming is VFIO's problem and if VFIO can't > > > reliably reclaim a device it shouldn't create it in the first place. > > > > I think that as far as device reclaiming was concerned the question > > posed was related to memory attributes of transactions for guest > > mappings and the related grouping/ordering with device reset MMIO > > transactions - it was not (or wasn't only) about error containment. > > Yes. It is VFIO that issues the reset, it is VFIO that must provide > the ordering under the assumption that NORMAL_NC was used. And does it? Because VFIO so far only assumes Device-nGnRnE. Do we need to address this first before attempting to change KVM? Sorry, just questions, trying to clear the roadblocks. -- Catalin