Re: [PATCH 3/5] x86_64/mm: map and unmap page tables in share_hotadd_m2p_table

[Hongyan Xia <hx242@xxxxxxx>]

On Wed, 2020-04-01 at 14:29 +0200, Jan Beulich wrote:
> On 23.03.2020 10:41, Hongyan Xia wrote:
> > --- a/xen/include/asm-x86/page.h
> > +++ b/xen/include/asm-x86/page.h
> > @@ -196,6 +196,24 @@ static inline l4_pgentry_t
> > l4e_from_paddr(paddr_t pa, unsigned int flags)
> >  #define map_l2t_from_l3e(x)        (l2_pgentry_t
> > *)map_domain_page(l3e_get_mfn(x))
> >  #define map_l3t_from_l4e(x)        (l3_pgentry_t
> > *)map_domain_page(l4e_get_mfn(x))
> >  
> > +#define l1e_from_l2e(l2e, off) ({                   \
> > +        l1_pgentry_t *l1t = map_l1t_from_l2e(l2e);  \
> > +        l1_pgentry_t l1e = l1t[off];                \
> > +        UNMAP_DOMAIN_PAGE(l1t);                     \
> > +        l1e; })
> > +
> > +#define l2e_from_l3e(l3e, off) ({                   \
> > +        l2_pgentry_t *l2t = map_l2t_from_l3e(l3e);  \
> > +        l2_pgentry_t l2e = l2t[off];                \
> > +        UNMAP_DOMAIN_PAGE(l2t);                     \
> > +        l2e; })
> > +
> > +#define l3e_from_l4e(l4e, off) ({                   \
> > +        l3_pgentry_t *l3t = map_l3t_from_l4e(l4e);  \
> > +        l3_pgentry_t l3e = l3t[off];                \
> > +        UNMAP_DOMAIN_PAGE(l3t);                     \
> > +        l3e; })
> 
> There's a reason these are macros rather than inline functions,
> I assume? (This reason would be nice to be stated in the
> description.)

While converting them into inline functions, I realised I cannot do
that due to the header mess. Converting into inline functions needs the
domain_page.h header, which opens a can of worms if I include it here
(page.h). Keeping them as macros works around this issue.

I will add this in the description.

Hongyan