Commit 5cec7537 authored by David Woodhouse's avatar David Woodhouse
Browse files

iommu/vt-d: Implement SVM_FLAG_SUPERVISOR_MODE for kernel access 



This is only usable for the static 1:1 mapping of physical memory.

Any access to vmalloc or module regions will require some way of doing
an IOTLB flush. It's theoretically possible to hook into the
tlb_flush_kernel_range() function, but that seems like overkill — most
of the addresses accessed through a kernel PASID *will* be in the 1:1
mapping.

If we really need to allow access to more interesting kernel regions,
then the answer will probably be an explicit IOTLB flush call after use,
akin to the DMA API's unmap function.

In fact, it might be worth introducing that sooner rather than later, and
making it just BUG() if the address isn't in the static 1:1 mapping.

Signed-off-by: default avatarDavid Woodhouse <David.Woodhouse@intel.com>
parent 569e4f77

drivers/iommu/intel-svm.c

+31 −12
Original line number Diff line number Diff line
@@ -269,11 +269,10 @@ int intel_svm_bind_mm(struct device *dev, int *pasid, int flags, struct svm_dev_ 
	struct intel_iommu *iommu = intel_svm_device_to_iommu(dev);

	struct intel_svm_dev *sdev;

	struct intel_svm *svm = NULL;

	struct mm_struct *mm = NULL;

	int pasid_max;

	int ret;



	BUG_ON(pasid && !current->mm);



	if (WARN_ON(!iommu))

		return -EINVAL;
@@ -284,12 +283,20 @@ int intel_svm_bind_mm(struct device *dev, int *pasid, int flags, struct svm_dev_ 
	} else

		pasid_max = 1 << 20;



	if ((flags & SVM_FLAG_SUPERVISOR_MODE)) {

		if (!ecap_srs(iommu->ecap))

			return -EINVAL;

	} else if (pasid) {

		mm = get_task_mm(current);

		BUG_ON(!mm);

	}



	mutex_lock(&pasid_mutex);

	if (pasid && !(flags & SVM_FLAG_PRIVATE_PASID)) {

		int i;



		idr_for_each_entry(&iommu->pasid_idr, svm, i) {

			if (svm->mm != current->mm ||

			if (svm->mm != mm ||

			    (svm->flags & SVM_FLAG_PRIVATE_PASID))

				continue;
@@ -355,17 +362,22 @@ int intel_svm_bind_mm(struct device *dev, int *pasid, int flags, struct svm_dev_ 
		}

		svm->pasid = ret;

		svm->notifier.ops = &intel_mmuops;

		svm->mm = get_task_mm(current);

		svm->mm = mm;

		svm->flags = flags;

		INIT_LIST_HEAD_RCU(&svm->devs);

		ret = -ENOMEM;

		if (!svm->mm || (ret = mmu_notifier_register(&svm->notifier, svm->mm))) {

		if (mm) {

			ret = mmu_notifier_register(&svm->notifier, mm);

			if (ret) {

				idr_remove(&svm->iommu->pasid_idr, svm->pasid);

				kfree(svm);

				kfree(sdev);

				goto out;

			}

		iommu->pasid_table[svm->pasid].val = (u64)__pa(svm->mm->pgd) | 1;

			iommu->pasid_table[svm->pasid].val = (u64)__pa(mm->pgd) | 1;

			mm = NULL;

		} else

			iommu->pasid_table[svm->pasid].val = (u64)__pa(init_mm.pgd) | 1 | (1ULL << 11);

		wmb();

	}

	list_add_rcu(&sdev->list, &svm->devs);
@@ -375,6 +387,8 @@ int intel_svm_bind_mm(struct device *dev, int *pasid, int flags, struct svm_dev_ 
	ret = 0;

 out:

	mutex_unlock(&pasid_mutex);

	if (mm)

		mmput(mm);

	return ret;

}

EXPORT_SYMBOL_GPL(intel_svm_bind_mm);
@@ -416,6 +430,7 @@ int intel_svm_unbind_mm(struct device *dev, int pasid) 
					mmu_notifier_unregister(&svm->notifier, svm->mm);



					idr_remove(&svm->iommu->pasid_idr, svm->pasid);

					if (svm->mm)

						mmput(svm->mm);

					/* We mandate that no page faults may be outstanding

					 * for the PASID when intel_svm_unbind_mm() is called.
@@ -500,6 +515,10 @@ static irqreturn_t prq_event_thread(int irq, void *d) 
		}



		result = QI_RESP_INVALID;

		/* Since we're using init_mm.pgd directly, we should never take

		 * any faults on kernel addresses. */

		if (!svm->mm)

			goto bad_req;

		down_read(&svm->mm->mmap_sem);

		vma = find_extend_vma(svm->mm, address);

		if (!vma || address < vma->vm_start)

include/linux/intel-svm.h

+14 −1
Original line number Diff line number Diff line
@@ -42,6 +42,19 @@ struct svm_dev_ops { 
 */

#define SVM_FLAG_PRIVATE_PASID		(1<<0)



/*

 * The SVM_FLAG_SUPERVISOR_MODE flag requests a PASID which can be used only

 * for access to kernel addresses. No IOTLB flushes are automatically done

 * for kernel mappings; it is valid only for access to the kernel's static

 * 1:1 mapping of physical memory — not to vmalloc or even module mappings.

 * A future API addition may permit the use of such ranges, by means of an

 * explicit IOTLB flush call (akin to the DMA API's unmap method).

 *

 * It is unlikely that we will ever hook into flush_tlb_kernel_range() to

 * do such IOTLB flushes automatically.

 */

#define SVM_FLAG_SUPERVISOR_MODE	(1<<1)



/**

 * intel_svm_bind_mm() - Bind the current process to a PASID

 * @dev:	Device to be granted acccess

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