Hi Peter, Thanks for looking into my patches.
On 07/11/2018 10:48 AM, Peter Xu wrote: > On Mon, Jul 09, 2018 at 01:22:50PM +0800, Lu Baolu wrote: > > [...] > >> +#ifndef __INTEL_PASID_H >> +#define __INTEL_PASID_H >> + >> +#define PASID_MIN 0x1 >> +#define PASID_MAX 0x20000 > Could I ask whether there's a reason to explicitly use 0x20000 for the > max value? Asked since I saw that the example in the spec gave 20 > bits for PASID (please refer to spec ver 3.0 section 3.4.3 figure > 3-8). Also I believe that's what I was told by Kevin. > > I saw that the old per-iommu max value is set to 0x20000, though I'm > not sure whether that's still needed since if we're going to have > two-level pasid table then AFAIU we don't need physically continuous > memory any more (though I saw that we don't yet have two-level pasid > table implemented): > > /* Eventually I'm promised we will get a multi-level PASID table > * and it won't have to be physically contiguous. Until then, > * limit the size because 8MiB contiguous allocations can be hard > * to come by. The limit of 0x20000, which is 1MiB for each of > * the PASID and PASID-state tables, is somewhat arbitrary. */ > if (iommu->pasid_max > 0x20000) > iommu->pasid_max = 0x20000; You are right. With the scalable mode defined in vt-d v3.0, wecould use the full 20 bit pasid. Previous max pasid was intended to save contiguous physical memory. Best regards, Lu Baolu _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
