From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-by2on0115.outbound.protection.outlook.com ([207.46.100.115]:56713 "EHLO na01-by2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753625AbbEAPXf convert rfc822-to-8bit (ORCPT ); Fri, 1 May 2015 11:23:35 -0400 From: Stuart Yoder To: Will Deacon , Varun Sethi CC: Marc Zyngier , "Minghuan.Lian@freescale.com" , "linux-pci@vger.kernel.org" , Arnd Bergmann , "Mingkai.Hu@freescale.com" , Roy Zang , Bjorn Helgaas , Scott Wood , "linux-arm-kernel@lists.infradead.org" , Alex Williamson Subject: RE: [PATCH 1/2] irqchip/gicv3-its: Support share device ID Date: Fri, 1 May 2015 15:23:31 +0000 Message-ID: References: <20150422170718.GG13019@arm.com> <20150424161818.GC7313@arm.com> <553A72D4.7000801@arm.com> <20150425113930.7386a42a@arm.com> <553DEC20.3010400@arm.com> <20150427170423.GC3310@arm.com> In-Reply-To: <20150427170423.GC3310@arm.com> Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org List-ID: > -----Original Message----- > From: Will Deacon [mailto:will.deacon@arm.com] > Sent: Monday, April 27, 2015 12:04 PM > To: Sethi Varun-B16395 > Cc: Marc Zyngier; Yoder Stuart-B08248; Lian Minghuan-B31939; linux-pci@vger.kernel.org; Arnd Bergmann; Hu > Mingkai-B21284; Zang Roy-R61911; Bjorn Helgaas; Wood Scott-B07421; linux-arm-kernel@lists.infradead.org > Subject: Re: [PATCH 1/2] irqchip/gicv3-its: Support share device ID > > On Mon, Apr 27, 2015 at 02:08:10PM +0100, Varun Sethi wrote: > > > >>> In the SMMU/GIC-500-ITS world the iommu isolation ID (the stream ID) > > > >>> and the GIC-ITS device ID are in fact the same ID. > > > >> > > > >> The DeviceID is the "MSI group" you mention. This is what provides > > > >> isolation at the ITS level. > > > >> > > > > [varun] True, in case of a transparent host bridge device Id won't > > > > provide the necessary isolation. > > > > > > Well, it depends how you look at it. How necessary is this isolation, since > > > we've already established that you couldn't distinguish between these > > > devices at the IOMMU level? > > > > > [varun] Yes, the devices would fall in the same IOMMU group. So, devices > > would end up sharing the interrupt? > > Well, I think that's the crux of the issue here. If IOMMU groups are also > needed to relay constraints to the IRQ subsystem, then perhaps we need a > more general notion of device grouping and ID transformations between > the different levels of group hierarchy. I agree. Have been thinking about it over the last few days...is is a matter of renaming what we currently call an "IOMMU group"? Or, do we really need to separate general 'device grouping' and 'iommu groups' in the Linux kernel? Stuart From mboxrd@z Thu Jan 1 00:00:00 1970 From: stuart.yoder@freescale.com (Stuart Yoder) Date: Fri, 1 May 2015 15:23:31 +0000 Subject: [PATCH 1/2] irqchip/gicv3-its: Support share device ID In-Reply-To: <20150427170423.GC3310@arm.com> References: <20150422170718.GG13019@arm.com> <20150424161818.GC7313@arm.com> <553A72D4.7000801@arm.com> <20150425113930.7386a42a@arm.com> <553DEC20.3010400@arm.com> <20150427170423.GC3310@arm.com> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org > -----Original Message----- > From: Will Deacon [mailto:will.deacon at arm.com] > Sent: Monday, April 27, 2015 12:04 PM > To: Sethi Varun-B16395 > Cc: Marc Zyngier; Yoder Stuart-B08248; Lian Minghuan-B31939; linux-pci at vger.kernel.org; Arnd Bergmann; Hu > Mingkai-B21284; Zang Roy-R61911; Bjorn Helgaas; Wood Scott-B07421; linux-arm-kernel at lists.infradead.org > Subject: Re: [PATCH 1/2] irqchip/gicv3-its: Support share device ID > > On Mon, Apr 27, 2015 at 02:08:10PM +0100, Varun Sethi wrote: > > > >>> In the SMMU/GIC-500-ITS world the iommu isolation ID (the stream ID) > > > >>> and the GIC-ITS device ID are in fact the same ID. > > > >> > > > >> The DeviceID is the "MSI group" you mention. This is what provides > > > >> isolation at the ITS level. > > > >> > > > > [varun] True, in case of a transparent host bridge device Id won't > > > > provide the necessary isolation. > > > > > > Well, it depends how you look at it. How necessary is this isolation, since > > > we've already established that you couldn't distinguish between these > > > devices at the IOMMU level? > > > > > [varun] Yes, the devices would fall in the same IOMMU group. So, devices > > would end up sharing the interrupt? > > Well, I think that's the crux of the issue here. If IOMMU groups are also > needed to relay constraints to the IRQ subsystem, then perhaps we need a > more general notion of device grouping and ID transformations between > the different levels of group hierarchy. I agree. Have been thinking about it over the last few days...is is a matter of renaming what we currently call an "IOMMU group"? Or, do we really need to separate general 'device grouping' and 'iommu groups' in the Linux kernel? Stuart