Commit e7d6fff6 authored by Will Deacon's avatar Will Deacon Committed by Joerg Roedel
Browse files

iommu: Use bitmap to calculate page size in iommu_pgsize() 



Avoid the potential for shifting values by amounts greater than the
width of their type by using a bitmap to compute page size in
iommu_pgsize().

Signed-off-by: default avatarWill Deacon <will@kernel.org>
Signed-off-by: default avatarIsaac J. Manjarres <isaacm@codeaurora.org>
Signed-off-by: default avatarGeorgi Djakov <quic_c_gdjako@quicinc.com>
Reviewed-by: default avatarLu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/1623850736-389584-6-git-send-email-quic_c_gdjako@quicinc.com


Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
parent 910c4406

drivers/iommu/iommu.c

+12 −19
Original line number Diff line number Diff line
@@ -8,6 +8,7 @@ 


#include <linux/device.h>

#include <linux/kernel.h>

#include <linux/bits.h>

#include <linux/bug.h>

#include <linux/types.h>

#include <linux/init.h>
@@ -2378,30 +2379,22 @@ static size_t iommu_pgsize(struct iommu_domain *domain, 
			   unsigned long addr_merge, size_t size)

{

	unsigned int pgsize_idx;

	unsigned long pgsizes;

	size_t pgsize;



	/* Max page size that still fits into 'size' */

	pgsize_idx = __fls(size);

	/* Page sizes supported by the hardware and small enough for @size */

	pgsizes = domain->pgsize_bitmap & GENMASK(__fls(size), 0);



	/* need to consider alignment requirements ? */

	if (likely(addr_merge)) {

		/* Max page size allowed by address */

		unsigned int align_pgsize_idx = __ffs(addr_merge);

		pgsize_idx = min(pgsize_idx, align_pgsize_idx);

	}



	/* build a mask of acceptable page sizes */

	pgsize = (1UL << (pgsize_idx + 1)) - 1;



	/* throw away page sizes not supported by the hardware */

	pgsize &= domain->pgsize_bitmap;

	/* Constrain the page sizes further based on the maximum alignment */

	if (likely(addr_merge))

		pgsizes &= GENMASK(__ffs(addr_merge), 0);



	/* make sure we're still sane */

	BUG_ON(!pgsize);

	/* Make sure we have at least one suitable page size */

	BUG_ON(!pgsizes);



	/* pick the biggest page */

	pgsize_idx = __fls(pgsize);

	pgsize = 1UL << pgsize_idx;

	/* Pick the biggest page size remaining */

	pgsize_idx = __fls(pgsizes);

	pgsize = BIT(pgsize_idx);



	return pgsize;

}