iommu/vt-d: Limit max address mask to MAX_AGAW_PFN_WIDTH

Address mask specifies the number of low order bits of the address field
that must be masked for the invalidation operation.

Since address bits masked start from bit 12, the max address mask should
be MAX_AGAW_PFN_WIDTH, as defined in Table 19 ("Invalidate Descriptor
Address Mask Encodings") of the spec.

Limit the max address mask returned from calculate_psi_aligned_address()
to MAX_AGAW_PFN_WIDTH to prevent potential integer overflow in the
following code:

qi_flush_dev_iotlb():
    ...
    addr |= (1ULL << (VTD_PAGE_SHIFT + mask - 1)) - 1;
    ...

Fixes: c4d27ffa ("iommu/vt-d: Add cache tag invalidation helpers")
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20240709152643.28109-2-baolu.lu@linux.intel.comSigned-off-by: Will Deacon <will@kernel.org>

drivers/iommu/intel/cache.c

@@ -245,7 +245,7 @@ static unsigned long calculate_psi_aligned_address(unsigned long start,
 		 * shared_bits are all equal in both pfn and end_pfn.
 		 */
 		shared_bits = ~(pfn ^ end_pfn) & ~bitmask;
-		mask = shared_bits ? __ffs(shared_bits) : BITS_PER_LONG;
+		mask = shared_bits ? __ffs(shared_bits) : MAX_AGAW_PFN_WIDTH;
 	}
 
 	*_pages = aligned_pages;