Commit 7a265361 authored Mar 27, 2020 by Christian Borntraeger

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: 3ac8e380 ("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>

parent f3dd18d4

Documentation/virt/kvm/api.rst

+6 −0

Original line number	Diff line number	Diff line
		@@ -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

arch/s390/mm/gmap.c

+5 −4

Original line number	Diff line number	Diff line
		@@ -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;

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