From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tom Lyon Subject: Re: [PATCH V2] 2.6.34: simple IOMMU API extension to check safe interrupt remapping Date: Fri, 2 Jul 2010 12:33:58 -0700 Message-ID: <201007021233.58894.pugs@lyon-about.com> References: <4c2d0790.Bi9FugC8c/QW1Ike%pugs@cisco.com> <20100702092646.GF24084@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Cc: "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" , "iommu@lists.linux-foundation.org" , "chrisw@sous-sol.org" , "mst@redhat.com" , "dwmw2@infradead.org" , "aafabbri@cisco.com" , "scofeldm@cisco.com" To: "Roedel, Joerg" Return-path: In-Reply-To: <20100702092646.GF24084@amd.com> Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Friday 02 July 2010 02:26:46 am Roedel, Joerg wrote: > On Thu, Jul 01, 2010 at 05:24:32PM -0400, Tom Lyon wrote: > > This patch allows IOMMU users to determine whether the hardware and software > > support safe, isolated interrupt remapping. Not all Intel IOMMUs have the > > hardware, and the software for AMD is not there yet. > > Signed-off-by: Tom Lyon > > It does not make a lot of sense to check for this feature in the > IOMMU-API currently because there is no support for intr-remapping in > there. But it will be there when intr-remapping support for AMD IOMMU is > implemented. So this change can be considered as a first step in that > direction. Please repost with the change requested below an I'll add > this one to my tree. OK, but I'm not sure what you mean by the first sentence. The Intel stuff today does intr remapping as a side effect of X2APIC support. > > > Version 2: previous ifdefs not needed. > > > > MST has convinced me that any user level driver for PCI master devices can't > > be safe unless there is an IOMMU protecting the APIC MSI/MSI-X interrupt > > addresses from device writes. This interrupt remapping is not present in all > > Intel IOMMUs and the code for the interrupt mapping in the AMD IOMMUs is not > > implemented yet. > > > > Needed by not-yet-accepted VFIO driver. > > > > diff -uprN linux-2.6.34/drivers/pci/intel-iommu.c iommuapi-linux-2.6.34/drivers/pci/intel-iommu.c > > --- linux-2.6.34/drivers/pci/intel-iommu.c 2010-05-16 14:17:36.000000000 -0700 > > +++ iommuapi-linux-2.6.34/drivers/pci/intel-iommu.c 2010-06-30 15:47:10.000000000 -0700 > > @@ -3705,6 +3705,10 @@ static int intel_iommu_domain_has_cap(st > > > > if (cap == IOMMU_CAP_CACHE_COHERENCY) > > return dmar_domain->iommu_snooping; > > + if (cap == IOMMU_CAP_SAFE_INTR_REMAP) > > + return intr_remapping_enabled; > > > > return 0; > > } > > diff -uprN linux-2.6.34/include/linux/iommu.h iommuapi-linux-2.6.34/include/linux/iommu.h > > --- linux-2.6.34/include/linux/iommu.h 2010-05-16 14:17:36.000000000 -0700 > > +++ iommuapi-linux-2.6.34/include/linux/iommu.h 2010-06-30 15:47:34.000000000 -0700 > > @@ -30,6 +30,7 @@ struct iommu_domain { > > }; > > > > #define IOMMU_CAP_CACHE_COHERENCY 0x1 > > +#define IOMMU_CAP_SAFE_INTR_REMAP 0x2 /* isolates device intrs */ > > I think the SAFE_ is not necessary in the name. It is misleading because > it indicates that there is an unsafe variant of intr-remapping available > when this capability is not set. Just call it IOMMU_CAP_INTR_REMAPPING. > > > Joerg >