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s390/gmap: return proper error code on ksm unsharing 

If a signal is pending we might return -ENOMEM instead of -EINTR.
We should propagate the proper error during KSM unsharing.
unmerge_ksm_pages returns -ERESTARTSYS on signal_pending. This gets
translated by entry.S to -EINTR. It is important to get this error
code so that userspace can retry.

To make this clearer we also add -EINTR to the documentation of the
PV_ENABLE call, which calls unmerge_ksm_pages.

Fixes: 3ac8e38015 ("s390/mm: disable KSM for storage key enabled pages")
Reviewed-by: Janosch Frank <frankja@linux.vnet.ibm.com>
Reported-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Tested-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
This commit is contained in:
Christian Borntraeger 2020-03-27 08:06:42 +01:00
parent f3dd18d444
commit 7a2653612b
2 changed files with 11 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
Documentation/virt/kvm/api.rst
View File

@ -4677,6 +4677,12 @@ KVM_PV_ENABLE
command has succeeded, any CPU added via hotplug will become
protected during its creation as well.
Errors:
===== =============================
EINTR an unmasked signal is pending
===== =============================
KVM_PV_DISABLE
Deregister the VM from the Ultravisor and reclaim the memory that

9
arch/s390/mm/gmap.c
View File

@ -2552,12 +2552,13 @@ int gmap_mark_unmergeable(void)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
int ret;
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;
}
ret = ksm_madvise(vma, vma->vm_start, vma->vm_end,
MADV_UNMERGEABLE, &vma->vm_flags);
if (ret)
return ret;
}
mm->def_flags &= ~VM_MERGEABLE;
return 0;