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 BC3856A320; Tue, 5 Dec 2023 17:50:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="L0Zo0NUd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2D990C433C8; Tue, 5 Dec 2023 17:50:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1701798630; bh=iHtPLJCrT8jVDogR2HcFk+3QsBCzCFBD9pyDf3NU5HU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=L0Zo0NUdsLKrYjTFRQ9QrCxszAMoQJQDwms7JS45EmNYS7SHFzRBvx17GquG1jp0Y CCndcwJFKrllSuEQPnzWxXjId704Gpi06HxtNVbXgdflqVvmynR9TxL56hOU/C+xTi E8qgUoPyvqQ55VomJwuxLnfCPnlCvSe+NFuzFzOU0/gByQuFrYVhYRaoHB5Drl+77w W0ABflwvllJtG76pscG/iSK1/F0R0Aum35XxBz4VO5yrfbA6e1DS4rJJ+8PmpGJbV6 w5QzBlI85shvIidEpnqzjEeOlyp7Dho5gdQlgMMo9TcSQv+7UM0VrHHEblVm1YEEUi ULAyqmJ+YmLLA== Received: from sofa.misterjones.org ([185.219.108.64] helo=goblin-girl.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1rAZYx-001eEi-Mp; Tue, 05 Dec 2023 17:50:27 +0000 Date: Tue, 05 Dec 2023 17:50:27 +0000 Message-ID: <86a5qobkt8.wl-maz@kernel.org> From: Marc Zyngier To: Catalin Marinas Cc: Jason Gunthorpe , 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, lpieralisi@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 In-Reply-To: References: <20231205033015.10044-1-ankita@nvidia.com> <86fs0hatt3.wl-maz@kernel.org> <20231205130517.GD2692119@nvidia.com> <20231205164318.GG2692119@nvidia.com> <86bkb4bn2v.wl-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/29.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: catalin.marinas@arm.com, jgg@nvidia.com, ankita@nvidia.com, shameerali.kolothum.thodi@huawei.com, 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, lpieralisi@kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false On Tue, 05 Dec 2023 17:33:01 +0000, Catalin Marinas wrote: > > On Tue, Dec 05, 2023 at 05:01:28PM +0000, Marc Zyngier wrote: > > On Tue, 05 Dec 2023 16:43:18 +0000, > > Jason Gunthorpe wrote: > > > On Tue, Dec 05, 2023 at 04:22:33PM +0000, Catalin Marinas wrote: > > > > That's an argument to restrict this feature to PCIe. It's really about > > > > fewer arguments on the behaviour of other devices. Marc did raise > > > > another issue with the GIC VCPU interface (does this even have a vma in > > > > the host VMM?). That's a class of devices where the mapping is > > > > context-switched, so the TLBI+DSB rules don't help. > > > > There is no vma. The CPU interface is entirely under control of KVM. > > Userspace only provides the IPA for the mapping. > > That's good to know. We can solve the GIC issue by limiting the > relaxation to those mappings that have a user vma. Yes, this should definitely be part of the decision. > Ideally we should do this for vfio only but we don't have an easy > way to convey this to KVM. But if we want to limit this to PCIe, we'll have to find out. The initial proposal (a long while ago) had a flag conveying some information, and I'd definitely feel more confident having something like that. M. -- Without deviation from the norm, progress is not possible.