[PATCH v3 11/37] KVM: s390: protvirt: Secure memory is not mergeable

Christian Borntraeger
2020-02-20T10:40:29Z

From: Janosch Frank <frankja@linux.ibm.com>

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@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
[borntraeger@de.ibm.com: patch merging, splitting, fixing]
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
arch/s390/include/asm/gmap.h | 1 +
arch/s390/kvm/kvm-s390.c | 7 +++++++
arch/s390/mm/gmap.c | 30 ++++++++++++++++++++----------
3 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/arch/s390/include/asm/gmap.h b/arch/s390/include/asm/gmap.h
index 3c4926aa78f4..6f9ff7a69fa2 100644
--- a/arch/s390/include/asm/gmap.h
+++ b/arch/s390/include/asm/gmap.h
@@ -148,4 +148,5 @@ 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 8272a821a621..f99e4eb5c27b 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2215,6 +2215,13 @@ static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd)
if (r)
break;

+ down_write(&current->mm->mmap_sem);
+ r = gmap_mark_unmergeable();
+ up_write(&current->mm->mmap_sem);
+ if (r) {
+ kvm_s390_pv_dealloc_vm(kvm);
+ break;
+ }
/* FMT 4 SIE needs esca */
r = sca_switch_to_extended(kvm);
if (r) {
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:
--
2.25.0