On Mon, Apr 05, 2021 at 12:11:05PM -0700, Isaac J. Manjarres wrote:
> From: Will Deacon <w...@kernel.org>
>
> 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: Will Deacon <w...@kernel.org>
> Signed-off-by: Isaac J. Manjarres <isa...@codeaurora.org>
> ---
> drivers/iommu/iommu.c | 31 ++++++++++++-------------------
> 1 file changed, 12 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index d0b0a15dba84..9006397b6604 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -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>
> @@ -2360,30 +2361,22 @@ 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_ULL(__fls(size), 0);
See my comments on the other thread, but I don't think it's necessary to use
the _ULL versions everywhere.
Will
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