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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=desiato.20200630; h=Sender:Content-Transfer-Encoding :Content-Type:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:Cc: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=8x8ci4zYO86l+iOoISJ73MuM18VIKViZ13UAubouy8E=; b=pTj9Wx8Rf+XYVTKGcQQJW8gUm G2qbm8xfCgHHTVU4bhDuCTv8o8JfnrL5UhGoUoLQ2S0I1eRKY/Ag7/NXXEf6b8ct2bckMqvad7snY SJPkEnMWt8u3dUEnXDhuHtnJHK4P1LbcmIB5b0s6XKVJV+EhZOLvJLC1oZkCTAazIsRVXXfvNnkIU IqWA1Rb35rTpgPtmQSbr3iXGQXmnb6jHle+AmSkXP/EReIwja1ketV12UqyNgsjSLRRanh+NQf8O9 0BsI5cGgdoboVxTSMc+h0A5uw4HJk0IjF8bJXnfqiSqLxaJbb0Z7Q4nXtoN1JW/WKUn2CSilx1mIt eEgHQ303Q==; Received: from localhost ([::1] helo=desiato.infradead.org) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lRcqD-006uPw-6f; Wed, 31 Mar 2021 15:33:09 +0000 Received: from mail.kernel.org ([198.145.29.99]) by desiato.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1lRcq8-006uPC-DE for linux-arm-kernel@lists.infradead.org; Wed, 31 Mar 2021 15:33:06 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8E51260FEC; Wed, 31 Mar 2021 15:33:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1617204782; bh=VEAokRAUwmqk6b1XNvz8xq2ssgOe8XarXhR7rguGo64=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=CcBcHfkJsWOGdBJ54F4tHzTqX8odPThBv/+nD0XArAtpvbHrAUS3tfD4yLFqBUaXA QIInRYII0xdx1nOaRk+v0SR3QhU7nQpWQvM9VNaJVeQhfC5WlD8XyuyDp4rA8fB3AC qzeNuO8OLYAUJTsUGZw7wRW0Gfsjg/mq1nhGmLolpbwE//OYgdwBNalxL0IxznuQrK utcZFNOfP8j+Phf/ENFUerPLJ0/uDGWVsR5mmQHpALnrqdH0ffLWfYgIIAPRdTOAnA 8dcoEDthoYC+/5HqphI9KhMkMzfNppf0PCUVFfgYM5FnvGgHzJ5E2cOcTyJ8oPhL3s OVTrYXihR510A== Date: Wed, 31 Mar 2021 16:32:57 +0100 From: Will Deacon To: Robin Murphy Cc: freedreno@lists.freedesktop.org, kvm@vger.kernel.org, Michael Ellerman , linuxppc-dev@lists.ozlabs.org, dri-devel@lists.freedesktop.org, Li Yang , iommu@lists.linux-foundation.org, netdev@vger.kernel.org, linux-arm-msm@vger.kernel.org, virtualization@lists.linux-foundation.org, David Woodhouse , Christoph Hellwig , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 16/18] iommu: remove DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE Message-ID: <20210331153256.GA7815@willie-the-truck> References: <20210316153825.135976-1-hch@lst.de> <20210316153825.135976-17-hch@lst.de> <20210330131149.GP5908@willie-the-truck> <20210330135801.GA6187@willie-the-truck> <578d6aa5-4239-f5d7-2e9f-686b18e52bba@arm.com> <20210331114947.GA7626@willie-the-truck> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210331_163304_867604_D31C7BDF X-CRM114-Status: GOOD ( 45.06 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 Wed, Mar 31, 2021 at 02:09:37PM +0100, Robin Murphy wrote: > On 2021-03-31 12:49, Will Deacon wrote: > > On Tue, Mar 30, 2021 at 05:28:19PM +0100, Robin Murphy wrote: > > > On 2021-03-30 14:58, Will Deacon wrote: > > > > On Tue, Mar 30, 2021 at 02:19:38PM +0100, Robin Murphy wrote: > > > > > On 2021-03-30 14:11, Will Deacon wrote: > > > > > > On Tue, Mar 16, 2021 at 04:38:22PM +0100, Christoph Hellwig wrote: > > > > > > > From: Robin Murphy > > > > > > > > > > > > > > Instead make the global iommu_dma_strict paramete in iommu.c canonical by > > > > > > > exporting helpers to get and set it and use those directly in the drivers. > > > > > > > > > > > > > > This make sure that the iommu.strict parameter also works for the AMD and > > > > > > > Intel IOMMU drivers on x86. As those default to lazy flushing a new > > > > > > > IOMMU_CMD_LINE_STRICT is used to turn the value into a tristate to > > > > > > > represent the default if not overriden by an explicit parameter. > > > > > > > > > > > > > > Signed-off-by: Robin Murphy . > > > > > > > [ported on top of the other iommu_attr changes and added a few small > > > > > > > missing bits] > > > > > > > Signed-off-by: Christoph Hellwig > > > > > > > --- > > > > > > > drivers/iommu/amd/iommu.c | 23 +------- > > > > > > > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 50 +--------------- > > > > > > > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 1 - > > > > > > > drivers/iommu/arm/arm-smmu/arm-smmu.c | 27 +-------- > > > > > > > drivers/iommu/dma-iommu.c | 9 +-- > > > > > > > drivers/iommu/intel/iommu.c | 64 ++++----------------- > > > > > > > drivers/iommu/iommu.c | 27 ++++++--- > > > > > > > include/linux/iommu.h | 4 +- > > > > > > > 8 files changed, 40 insertions(+), 165 deletions(-) > > > > > > > > > > > > I really like this cleanup, but I can't help wonder if it's going in the > > > > > > wrong direction. With SoCs often having multiple IOMMU instances and a > > > > > > distinction between "trusted" and "untrusted" devices, then having the > > > > > > flush-queue enabled on a per-IOMMU or per-domain basis doesn't sound > > > > > > unreasonable to me, but this change makes it a global property. > > > > > > > > > > The intent here was just to streamline the existing behaviour of stuffing a > > > > > global property into a domain attribute then pulling it out again in the > > > > > illusion that it was in any way per-domain. We're still checking > > > > > dev_is_untrusted() before making an actual decision, and it's not like we > > > > > can't add more factors at that point if we want to. > > > > > > > > Like I say, the cleanup is great. I'm just wondering whether there's a > > > > better way to express the complicated logic to decide whether or not to use > > > > the flush queue than what we end up with: > > > > > > > > if (!cookie->fq_domain && (!dev || !dev_is_untrusted(dev)) && > > > > domain->ops->flush_iotlb_all && !iommu_get_dma_strict()) > > > > > > > > which is mixing up globals, device properties and domain properties. The > > > > result is that the driver code ends up just using the global to determine > > > > whether or not to pass IO_PGTABLE_QUIRK_NON_STRICT to the page-table code, > > > > which is a departure from the current way of doing things. > > > > > > But previously, SMMU only ever saw the global policy piped through the > > > domain attribute by iommu_group_alloc_default_domain(), so there's no > > > functional change there. > > > > For DMA domains sure, but I don't think that's the case for unmanaged > > domains such as those used by VFIO. > > Eh? This is only relevant to DMA domains anyway. Flush queues are part of > the IOVA allocator that VFIO doesn't even use. It's always been the case > that unmanaged domains only use strict invalidation. Maybe I'm going mad. With this patch, the SMMU driver unconditionally sets IO_PGTABLE_QUIRK_NON_STRICT for page-tables if iommu_get_dma_strict() is true, no? In which case, that will get set for page-tables corresponding to unmanaged domains as well as DMA domains when it is enabled. That didn't happen before because you couldn't set the attribute for unmanaged domains. What am I missing? > > > Obviously some of the above checks could be factored out into some kind of > > > iommu_use_flush_queue() helper that IOMMU drivers can also call if they need > > > to keep in sync. Or maybe we just allow iommu-dma to set > > > IO_PGTABLE_QUIRK_NON_STRICT directly via iommu_set_pgtable_quirks() if we're > > > treating that as a generic thing now. > > > > I think a helper that takes a domain would be a good starting point. > > You mean device, right? The one condition we currently have is at the device > level, and there's really nothing inherent to the domain itself that matters > (since the type is implicitly IOMMU_DOMAIN_DMA to even care about this). Device would probably work too; you'd pass the first device to attach to the domain when querying this from the SMMU driver, I suppose. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel