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Commit 91017044 authored by David Woodhouse's avatar David Woodhouse
Browse files

iommu/vt-d: Fix PASID table allocation 



Somehow I ended up with an off-by-three error in calculating the size of
the PASID and PASID State tables, which triggers allocations failures as
those tables unfortunately have to be physically contiguous.

In fact, even the *correct* maximum size of 8MiB is problematic and is
wont to lead to allocation failures. Since I have extracted a promise
that this *will* be fixed in hardware, I'm happy to limit it on the
current hardware to a maximum of 0x20000 PASIDs, which gives us 1MiB
tables — still not ideal, but better than before.

Reported by Mika Kuoppala <mika.kuoppala@linux.intel.com> and also by
Xunlei Pang <xlpang@redhat.com> who submitted a simpler patch to fix
only the allocation (and not the free) to the "correct" limit... which
was still problematic.

Signed-off-by: default avatarDavid Woodhouse <dwmw2@infradead.org>
Cc: stable@vger.kernel.org
parent 1c387188

drivers/iommu/intel-svm.c

+17 −11
Original line number Diff line number Diff line
@@ -39,10 +39,18 @@ int intel_svm_alloc_pasid_tables(struct intel_iommu *iommu) 
	struct page *pages;

	int order;



	order = ecap_pss(iommu->ecap) + 7 - PAGE_SHIFT;

	if (order < 0)

		order = 0;



	/* Start at 2 because it's defined as 2^(1+PSS) */

	iommu->pasid_max = 2 << ecap_pss(iommu->ecap);



	/* 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;



	order = get_order(sizeof(struct pasid_entry) * iommu->pasid_max);

	pages = alloc_pages(GFP_KERNEL | __GFP_ZERO, order);

	if (!pages) {

		pr_warn("IOMMU: %s: Failed to allocate PASID table\n",
@@ -53,6 +61,8 @@ int intel_svm_alloc_pasid_tables(struct intel_iommu *iommu) 
	pr_info("%s: Allocated order %d PASID table.\n", iommu->name, order);



	if (ecap_dis(iommu->ecap)) {

		/* Just making it explicit... */

		BUILD_BUG_ON(sizeof(struct pasid_entry) != sizeof(struct pasid_state_entry));

		pages = alloc_pages(GFP_KERNEL | __GFP_ZERO, order);

		if (pages)

			iommu->pasid_state_table = page_address(pages);
@@ -68,11 +78,7 @@ int intel_svm_alloc_pasid_tables(struct intel_iommu *iommu) 


int intel_svm_free_pasid_tables(struct intel_iommu *iommu)

{

	int order;



	order = ecap_pss(iommu->ecap) + 7 - PAGE_SHIFT;

	if (order < 0)

		order = 0;

	int order = get_order(sizeof(struct pasid_entry) * iommu->pasid_max);



	if (iommu->pasid_table) {

		free_pages((unsigned long)iommu->pasid_table, order);
@@ -371,8 +377,8 @@ int intel_svm_bind_mm(struct device *dev, int *pasid, int flags, struct svm_dev_ 
		}

		svm->iommu = iommu;



		if (pasid_max > 2 << ecap_pss(iommu->ecap))

			pasid_max = 2 << ecap_pss(iommu->ecap);

		if (pasid_max > iommu->pasid_max)

			pasid_max = iommu->pasid_max;



		/* Do not use PASID 0 in caching mode (virtualised IOMMU) */

		ret = idr_alloc(&iommu->pasid_idr, svm,

include/linux/intel-iommu.h

+1 −0
Original line number Diff line number Diff line
@@ -429,6 +429,7 @@ struct intel_iommu { 
	struct page_req_dsc *prq;

	unsigned char prq_name[16];    /* Name for PRQ interrupt */

	struct idr pasid_idr;

	u32 pasid_max;

#endif

	struct q_inval  *qi;            /* Queued invalidation info */

	u32 *iommu_state; /* Store iommu states between suspend and resume.*/