On 13.07.2018 08:37, Janosch Frank wrote:
> Let's allow huge pmd linking when enabled through the
> KVM_CAP_S390_HPAGE_1M capability. Also we can now restrict gmap
> invalidation and notification to the cases where the capability has
> been activated and save some cycles when that's not the case.
>
> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
> ---
> arch/s390/mm/gmap.c | 9 ++++++---
> arch/s390/mm/pgtable.c | 12 ++++++------
> 2 files changed, 12 insertions(+), 9 deletions(-)
>
> diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
> index 8b1a293b00d3..1399392d2fbd 100644
> --- a/arch/s390/mm/gmap.c
> +++ b/arch/s390/mm/gmap.c
> @@ -2,8 +2,10 @@
> /*
> * KVM guest address space mapping code
> *
> - * Copyright IBM Corp. 2007, 2016
> + * Copyright IBM Corp. 2007, 2016, 2018
> * Author(s): Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
> + * David Hildenbrand <david@xxxxxxxxxx>
> + * Janosch Frank <frankja@xxxxxxxxxxxxxxxxxx>
> */
>
> #include <linux/kernel.h>
> @@ -589,8 +591,8 @@ int __gmap_link(struct gmap *gmap, unsigned long gaddr, unsigned long vmaddr)
> return -EFAULT;
> pmd = pmd_offset(pud, vmaddr);
> VM_BUG_ON(pmd_none(*pmd));
> - /* large pmds cannot yet be handled */
> - if (pmd_large(*pmd))
> + /* Are we allowed to use huge pages? */
> + if (pmd_large(*pmd) && !gmap->mm->context.allow_gmap_hpage_1m)
> return -EFAULT;
> /* Link gmap segment table entry location to page table. */
> rc = radix_tree_preload(GFP_KERNEL);
> @@ -1631,6 +1633,7 @@ struct gmap *gmap_shadow(struct gmap *parent, unsigned long asce,
> unsigned long limit;
> int rc;
>
> + BUG_ON(parent->mm->context.allow_gmap_hpage_1m);
> BUG_ON(gmap_is_shadow(parent));
> spin_lock(&parent->shadow_lock);
> sg = gmap_find_shadow(parent, asce, edat_level);
> diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
> index 161e08437681..1275f73b5c39 100644
> --- a/arch/s390/mm/pgtable.c
> +++ b/arch/s390/mm/pgtable.c
> @@ -348,7 +348,7 @@ static inline void pmdp_idte_local(struct mm_struct *mm,
> mm->context.asce, IDTE_LOCAL);
> else
> __pmdp_idte(addr, pmdp, 0, 0, IDTE_LOCAL);
> - if (mm_has_pgste(mm))
> + if (mm_has_pgste(mm) && mm->context.allow_gmap_hpage_1m)
> gmap_pmdp_idte_local(mm, addr);
> }
>
> @@ -358,15 +358,15 @@ static inline void pmdp_idte_global(struct mm_struct *mm,
> if (MACHINE_HAS_TLB_GUEST) {
> __pmdp_idte(addr, pmdp, IDTE_NODAT | IDTE_GUEST_ASCE,
> mm->context.asce, IDTE_GLOBAL);
> - if (mm_has_pgste(mm))
> + if (mm_has_pgste(mm) && mm->context.allow_gmap_hpage_1m)
> gmap_pmdp_idte_global(mm, addr);
> } else if (MACHINE_HAS_IDTE) {
> __pmdp_idte(addr, pmdp, 0, 0, IDTE_GLOBAL);
> - if (mm_has_pgste(mm))
> + if (mm_has_pgste(mm) && mm->context.allow_gmap_hpage_1m)
> gmap_pmdp_idte_global(mm, addr);
> } else {
> __pmdp_csp(pmdp);
> - if (mm_has_pgste(mm))
> + if (mm_has_pgste(mm) && mm->context.allow_gmap_hpage_1m)
> gmap_pmdp_csp(mm, addr);
> }
> }
> @@ -435,7 +435,7 @@ pmd_t pmdp_xchg_direct(struct mm_struct *mm, unsigned long addr,
> pmd_t old;
>
> preempt_disable();
> - if (mm_has_pgste(mm)) {
> + if (mm_has_pgste(mm) && mm->context.allow_gmap_hpage_1m) {
> pmdp_clear_skeys(mm, pmdp, new);
> pmdp_notify(mm, addr);
> }
> @@ -452,7 +452,7 @@ pmd_t pmdp_xchg_lazy(struct mm_struct *mm, unsigned long addr,
> pmd_t old;
>
> preempt_disable();
> - if (mm_has_pgste(mm)) {
> + if (mm_has_pgste(mm) && mm->context.allow_gmap_hpage_1m) {
> pmdp_clear_skeys(mm, pmdp, new);
> pmdp_notify(mm, addr);
> }
>
You should probably change the order of the last two patches, so you
really only expose the capability if support for huge pages is there.
--
Thanks,
David / dhildenb
