Messages in this thread | | | From | Shameerali Kolothum Thodi <> | Subject | RE: [PATCH v1 01/14] iommu: Add iommu_get_unmanaged_domain helper | Date | Fri, 10 Mar 2023 15:44:02 +0000 |
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> -----Original Message----- > From: Jason Gunthorpe [mailto:jgg@nvidia.com] > Sent: 10 March 2023 15:33 > To: Eric Auger <eric.auger@redhat.com> > Cc: Nicolin Chen <nicolinc@nvidia.com>; robin.murphy@arm.com; > will@kernel.org; kevin.tian@intel.com; baolu.lu@linux.intel.com; > joro@8bytes.org; Shameerali Kolothum Thodi > <shameerali.kolothum.thodi@huawei.com>; jean-philippe@linaro.org; > linux-arm-kernel@lists.infradead.org; iommu@lists.linux.dev; > linux-kernel@vger.kernel.org > Subject: Re: [PATCH v1 01/14] iommu: Add iommu_get_unmanaged_domain > helper > > On Fri, Mar 10, 2023 at 11:14:59AM +0100, Eric Auger wrote: > > Hi Nicolin, > > > > On 3/9/23 11:53, Nicolin Chen wrote: > > > The nature of ITS virtualization on ARM is done via hypercalls, so > > > kernel handles all IOVA mappings for the MSI doorbell in > > > iommu_dma_prepare_msi() and iommu_dma_compose_msi_msg(). The > current > > > virtualization solution with a 2-stage nested translation setup is > > > to do 1:1 IOVA mappings at stage-1 > > Note that if we still intend to use that trick there is a known issue > > at kernel side that needs to be fixed. > > > > ARM DEN 0049E.b IORT specification mandates that when RMRs are > > present, the OS must preserve PCIe configuration performed by the boot > > FW. > > This limitation doesn't seem necessary for this MSI stuff? > > What is it for?
That is to make sure the Stream Ids specified in RMR are still valid and is not being reassigned by OS. The kernel checks for this(iort_rmr_has_dev()), https://lore.kernel.org/linux-arm-kernel/20220420164836.1181-5-shameerali.kolothum.thodi@huawei.com/
Thanks, Shameer
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