Re: [PATCH v2] s390/gmap: return proper error code on ksm unsharing

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On 27.03.20 10:23, Christian Borntraeger wrote:
> If a signal is pending we might return -ENOMEM instead of -EINTR.
> We should propagate the proper error during KSM unsharing.
> 
> Fixes: 3ac8e38015d4 ("s390/mm: disable KSM for storage key enabled pages")
> Reviewed-by: Janosch Frank <frankja@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> ---
>  arch/s390/mm/gmap.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
> index 27926a06df32..1ef864c252e6 100644
> --- a/arch/s390/mm/gmap.c
> +++ b/arch/s390/mm/gmap.c
> @@ -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;


After the qemu patch discussion I would add


diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 0e268b3d1591..ba8f9cbe4376 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -4680,6 +4680,12 @@ 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


and change the patch description to something like


    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.
    
    Fixes: 3ac8e38015d4 ("s390/mm: disable KSM for storage key enabled pages")
    Reviewed-by: Janosch Frank <frankja@xxxxxxxxxxxxxxxxxx>
    Reported-by: Marc Hartmayer <mhartmay@xxxxxxxxxxxxx>
    Tested-by: Marc Hartmayer <mhartmay@xxxxxxxxxxxxx>
    Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
    Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>




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