Hi, Joerg
Not sure whether you think this calculation is correct.
If I missed something for this " + 1" in your formula, I am glad to hear your
explanation. So that I could learn something from you :-)
Have a good day~
On Sat, May 21, 2016 at 02:41:51AM +0000, Wei Yang wrote:
>In commit <8bf478163e69> ("iommu/vt-d: Split up iommu->domains array"), it
>it splits iommu->domains in two levels. Each first level contains 256
>entries of second level. In case of the ndomains is exact a multiple of
>256, it would have one more extra first level entry for current
>implementation.
>
>This patch refines this calculation to reduce the extra first level entry.
>
>Signed-off-by: Wei Yang <[email protected]>
>---
> drivers/iommu/intel-iommu.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
>diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
>index e3061d3..2204ca4 100644
>--- a/drivers/iommu/intel-iommu.c
>+++ b/drivers/iommu/intel-iommu.c
>@@ -1634,7 +1634,7 @@ static int iommu_init_domains(struct intel_iommu *iommu)
> return -ENOMEM;
> }
>
>- size = ((ndomains >> 8) + 1) * sizeof(struct dmar_domain **);
>+ size = (ALIGN(ndomains, 256) >> 8) * sizeof(struct dmar_domain **);
> iommu->domains = kzalloc(size, GFP_KERNEL);
>
> if (iommu->domains) {
>@@ -1699,7 +1699,7 @@ static void disable_dmar_iommu(struct intel_iommu *iommu)
> static void free_dmar_iommu(struct intel_iommu *iommu)
> {
> if ((iommu->domains) && (iommu->domain_ids)) {
>- int elems = (cap_ndoms(iommu->cap) >> 8) + 1;
>+ int elems = ALIGN(cap_ndoms(iommu->cap), 256) >> 8;
> int i;
>
> for (i = 0; i < elems; i++)
>--
>1.7.9.5
--
Wei Yang
Help you, Help me
