On Thu, Apr 01, 2021 at 06:39:35PM -0700, isa...@codeaurora.org wrote: > On 2021-04-01 09:47, Will Deacon wrote: > > 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> > > --- > > 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..bcd623862bf9 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(__fls(size), 0); > I've fixed this in the latest RFC for the iommu_map/unmap optimization > patches, > but for the sake of completeness: I think this should be GENMASK_ULL, in > case > __fls(size) >= 32.
Hmm, but 'size' is a size_t; which architectures have sizeof(size_t) > sizeof(unsigned long)? > > - /* 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); This one looks like more of an issue, though, as addr_merge is a phys_addr_t, which certainly can be 64-bit where unsigned long is 32-bit (e.g. Armv7 + LPAE) Rather than make everything _ULL, please can you just do it where we're actually using the larger types? Will _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu