ANDROID: iommu: Define vendor hook to limit max alignment

When the IOVA framework applies IOVA alignment it aligns all IOVAs
to the smallest PAGE_SIZE order which is greater than or equal to
the requested IOVA size.

We support use cases that requires large buffers (> 64 MB in size)
to be allocated and mapped in their stage 1 page tables.  However,
with this alignment scheme we find ourselves running out of IOVA
space for 32 bit devices,

Define a vendor hook to allow limiting the alignment value used when
allocating IOVAs.

We addressed this issue in Android13-5.15 with commit 989b762eb159
("FROMLIST: iommu/iova: Add support for IOVA max alignment tuning")

Bug: 190519428
Change-Id: I13032c1b440c050860109aae23f96c0b52782664
Link: https://lore.kernel.org/r/1634148667-409263-1-git-send-email-quic_c_gdjako@quicinc.com/
Signed-off-by: Sukadev Bhattiprolu <quic_sukadev@quicinc.com>

drivers/android/vendor_hooks.c

@@ -114,6 +114,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_iommu_iovad_free_iova);
 EXPORT_TRACEPOINT_SYMBOL_GPL(android_rvh_psci_tos_resident_on);
 EXPORT_TRACEPOINT_SYMBOL_GPL(android_rvh_psci_cpu_suspend);
 EXPORT_TRACEPOINT_SYMBOL_GPL(android_rvh_iommu_iovad_init_alloc_algo);
+EXPORT_TRACEPOINT_SYMBOL_GPL(android_rvh_iommu_limit_align_shift);
 EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_ptype_head);
 EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_allow_domain_state);
 EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_cpuidle_psci_enter);

drivers/iommu/iova.c

@@ -173,8 +173,12 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
 	unsigned long align_mask = ~0UL;
 	unsigned long high_pfn = limit_pfn, low_pfn = iovad->start_pfn;
 
-	if (size_aligned)
-		align_mask <<= fls_long(size - 1);
+	if (size_aligned) {
+		unsigned long shift = fls_long(size - 1);
+
+		trace_android_rvh_iommu_limit_align_shift(iovad, size, &shift);
+		align_mask <<= shift;
+	}
 
 	/* Walk the tree backwards */
 	spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);

include/trace/hooks/iommu.h

@@ -39,6 +39,11 @@ DECLARE_RESTRICTED_HOOK(android_rvh_iommu_iovad_init_alloc_algo,
 	TP_PROTO(struct device *dev, struct iova_domain *iovad),
 	TP_ARGS(dev, iovad), 1);
 
+DECLARE_RESTRICTED_HOOK(android_rvh_iommu_limit_align_shift,
+	TP_PROTO(struct iova_domain *iovad, unsigned long size,
+		unsigned long *shift),
+	TP_ARGS(iovad, size, shift), 1);
+
 #endif /* _TRACE_HOOK_IOMMU_H */
 
 /* This part must be outside protection */