On 04.02.20 14:04, Christian Borntraeger wrote:
> From: Janosch Frank <frankja@xxxxxxxxxxxxx>
>
> KSM will not work on secure pages, because when the kernel reads a
> secure page, it will be encrypted and hence no two pages will look the
> same.
>
> Let's mark the guest pages as unmergeable when we transition to secure
> mode.
>
> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
> Reviewed-by: Thomas Huth <thuth@xxxxxxxxxx>
> ---
> arch/s390/include/asm/gmap.h | 1 +
> arch/s390/kvm/kvm-s390.c | 6 ++++++
> arch/s390/mm/gmap.c | 30 ++++++++++++++++++++----------
> 3 files changed, 27 insertions(+), 10 deletions(-)
>
> diff --git a/arch/s390/include/asm/gmap.h b/arch/s390/include/asm/gmap.h
> index e2d2f48c5c7c..e1f2cc0b2b00 100644
> --- a/arch/s390/include/asm/gmap.h
> +++ b/arch/s390/include/asm/gmap.h
> @@ -146,4 +146,5 @@ int gmap_mprotect_notify(struct gmap *, unsigned long start,
>
> void gmap_sync_dirty_log_pmd(struct gmap *gmap, unsigned long dirty_bitmap[4],
> unsigned long gaddr, unsigned long vmaddr);
> +int gmap_mark_unmergeable(void);
> #endif /* _ASM_S390_GMAP_H */
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 35f46404830f..741d81f57c3c 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -2181,6 +2181,12 @@ static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd)
> if (r)
> break;
>
> + down_write(¤t->mm->mmap_sem);
> + r = gmap_mark_unmergeable();
> + up_write(¤t->mm->mmap_sem);
> + if (r)
> + break;
> +
> mutex_lock(&kvm->lock);
> kvm_s390_vcpu_block_all(kvm);
> /* FMT 4 SIE needs esca */
> diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
> index edcdca97e85e..7291452fe5f0 100644
> --- a/arch/s390/mm/gmap.c
> +++ b/arch/s390/mm/gmap.c
> @@ -2548,6 +2548,22 @@ int s390_enable_sie(void)
> }
> EXPORT_SYMBOL_GPL(s390_enable_sie);
>
> +int gmap_mark_unmergeable(void)
> +{
> + struct mm_struct *mm = current->mm;
> + struct vm_area_struct *vma;
> +
> + for (vma = mm->mmap; vma; vma = vma->vm_next) {
> + if (ksm_madvise(vma, vma->vm_start, vma->vm_end,
> + MADV_UNMERGEABLE, &vma->vm_flags)) {
> + return -ENOMEM;
> + }
> + }
> + mm->def_flags &= ~VM_MERGEABLE;
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(gmap_mark_unmergeable);
> +
> /*
> * Enable storage key handling from now on and initialize the storage
> * keys with the default key.
> @@ -2593,7 +2609,6 @@ static const struct mm_walk_ops enable_skey_walk_ops = {
> int s390_enable_skey(void)
> {
> struct mm_struct *mm = current->mm;
> - struct vm_area_struct *vma;
> int rc = 0;
>
> down_write(&mm->mmap_sem);
> @@ -2601,16 +2616,11 @@ int s390_enable_skey(void)
> goto out_up;
>
> mm->context.uses_skeys = 1;
> - for (vma = mm->mmap; vma; vma = vma->vm_next) {
> - if (ksm_madvise(vma, vma->vm_start, vma->vm_end,
> - MADV_UNMERGEABLE, &vma->vm_flags)) {
> - mm->context.uses_skeys = 0;
> - rc = -ENOMEM;
> - goto out_up;
> - }
> + rc = gmap_mark_unmergeable();
> + if (rc) {
> + mm->context.uses_skeys = 0;
> + goto out_up;
> }
> - mm->def_flags &= ~VM_MERGEABLE;
> -
> walk_page_range(mm, 0, TASK_SIZE, &enable_skey_walk_ops, NULL);
>
> out_up:
>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
--
Thanks,
David / dhildenb
