Messages in this thread | | | Date | Tue, 18 Apr 2023 10:06:12 +0800 | Subject | Re: [PATCH v4 3/7] iommu: Support allocation of global PASIDs outside SVA | From | Baolu Lu <> |
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On 4/18/23 12:46 AM, Jacob Pan wrote: > On Wed, 12 Apr 2023 09:37:48 +0800, Baolu Lu<baolu.lu@linux.intel.com> > wrote: > >> On 4/11/23 4:02 PM, Tian, Kevin wrote: >>>> From: Jacob Pan<jacob.jun.pan@linux.intel.com> >>>> Sent: Saturday, April 8, 2023 2:06 AM >>>> @@ -28,8 +26,8 @@ static int iommu_sva_alloc_pasid(struct mm_struct >>>> *mm, ioasid_t min, ioasid_t ma >>>> goto out; >>>> } >>>> >>>> - ret = ida_alloc_range(&iommu_global_pasid_ida, min, max, >>>> GFP_KERNEL); >>>> - if (ret < min) >>>> + ret = iommu_alloc_global_pasid(min, max); >>> I wonder whether this can take a device pointer so >>> dev->iommu->max_pasids is enforced inside the alloc function. >> Agreed. Instead of using the open code, it looks better to have a helper >> like dev_iommu_max_pasids(). > yes, probably export dev_iommu_get_max_pasids(dev)? > > But if I understood Kevin correctly, he's also suggesting that the > interface should be changed to iommu_alloc_global_pasid(dev), my concern is > that how do we use this function to reserve RID_PASID which is not specific > to a device?
Probably we can introduce a counterpart dev->iommu->min_pasids, so that there's no need to reserve the RID_PASID. At present, we can set it to 1 in the core as ARM/AMD/Intel all treat PASID 0 as a special pasid.
In the future, if VT-d supports using arbitrary number as RID_PASID for any specific device, we can call iommu_alloc_global_pasid() for that device.
The device drivers don't know and don't need to know the range of viable PASIDs, so the @min, @max parameters seem to be unreasonable.
Best regards, baolu
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