lkml.org 
[lkml]   [2021]   [Jun]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v7 05/15] iommu: Use bitmap to calculate page size in iommu_pgsize()
From
Date
On 6/16/21 9:38 PM, Georgi Djakov wrote:
> From: Will Deacon <will@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 <will@kernel.org>
> Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>
> Signed-off-by: Georgi Djakov <quic_c_gdjako@quicinc.com>
> ---
> 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 5419c4b9f27a..80e471ada358 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>
> @@ -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;
> }
>

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>

Best regards,
baolu

\
 
 \ /
  Last update: 2021-06-17 09:18    [W:0.229 / U:0.036 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site