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

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On 27.03.20 11:23, Christian Borntraeger wrote:
> 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>
> 

Looks good.

-- 
Thanks,

David / dhildenb




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