Hi Jean, Thank you for the clarifications. In cases where a large range of PCI segments may be assigned to guest, would it make sense to describe this configuration as base + count. Currently, one would have to describe them individually.
Yinghan -----Original Message----- From: Jean-Philippe Brucker <jean-phili...@linaro.org> Sent: Thursday, November 5, 2020 5:45 AM To: Yinghan Yang <yinghan.y...@microsoft.com> Cc: iommu@lists.linux-foundation.org; Alexander Grest <alexander.gr...@microsoft.com>; eric.au...@redhat.com; jean-phili...@linaro.org; j...@8bytes.org; kevin.t...@intel.com; lorenzo.pieral...@arm.com; m...@redhat.com; Boeuf, Sebastien <sebastien.bo...@intel.com>; a...@redhat.com Subject: [EXTERNAL] Re: Question regarding VIOT proposal Hi, On Thu, Nov 05, 2020 at 12:13:53AM +0000, Yinghan Yang via iommu wrote: > Hi iommu developers, > > > > I have a question regarding the recent VIOT submission for supporting > paravirtualized IOMMU in guests. The spec defines PCI Range Node > Structure > (5.2.30.3) that maps to a single PCI segment. (To provide some context for other readers, a description of the node is available at https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fjpbrucker.net%2Fvirtio-iommu%2Fviot%2Fviot-v8.pdf&data=04%7C01%7CYinghan.Yang%40microsoft.com%7Cc52e42b3eb63495ed28708d881910b6f%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637401807671941922%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=YiZLS6kKMqe58vPsJFYIfA3nVICc3G44E6bziD3cC94%3D&reserved=0) > > > > Is it possible for the new table to express that an IOMMU covers all > PCI segments? This could help support scenarios where: > > > > 1. Devices are dynamically assigned to guests during runtime 2. > Devices in the same guests are assigned to different segments. This is possible with the current descriptor, assuming the PCI segments are static. The platform can provide a PCI Range Node for each segment, with a BDF range 0 - 0xffff. For example a table could describe: * PCI Range Node * PCI Segment: 0 * BDF start: 0 * BDF end: 0xffff * Endpoint start: 0 * Output node: &viommu * PCI Range Node * PCI Segment: 1 * BDF start: 0 * BDF end: 0xffff * Endpoint start: 0x10000 * Output node: &viommu * viommu Node Then the IOMMU covers all PCI devices on the two segments. To identify a device when configuring DMA translation, the IOMMU driver builds a 32-bit endpoint ID = Endpoint start + BDF. Thanks, Jean _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
