Re: [Xen-devel] [PATCH v3 1/2] x86/mm: factor out the code for shattering an l3 PTE

["Xia, Hongyan" <hongyxia@xxxxxxxxxx>]

On Wed, 2019-12-11 at 16:32 +0100, Jan Beulich wrote:
> On 11.12.2019 11:58, Hongyan Xia wrote:
> > @@ -5578,27 +5597,8 @@ int modify_xen_mappings(unsigned long s,
> > unsigned long e, unsigned int nf)
> >              }
> >  
> >              /* PAGE1GB: shatter the superpage and fall through. */
> > -            pl2e = alloc_xen_pagetable();
> > -            if ( !pl2e )
> > +            if ( shatter_l3e(pl3e, 0, locking) )
> >                  return -ENOMEM;
> 
> Hmm, I didn't expect I'd need to comment on this again: As per
> my v2 reply, you should hand on the return value from the
> function, not make up your own. This is so that in case the
> function gains another error path with a different error code,
> it wouldn't become indistinguishable to callers further up.
> 

I was basically thinking about the conversation we had that ENOMEM is
probably the only error value map_pages_to_xen would return ever, and
it is unlikely to gain another return value in the future, so initially
I just let shatter return -1 and the caller return -ENOMEM. There is no
problem for me if we want to change it to handle different error
values.

Hongyan
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