Re: [PATCH v2 5/5] xen/memory, tools: Make init-dom0less consume XEN_DOMCTL_get_mem_map

[Henry Wang <xin.wang2@xxxxxxx>]

Hi Jan,

On 3/12/2024 1:07 AM, Jan Beulich wrote:
> > +/*
> > + * Flag to force populate physmap to use pages from domheap instead of 1:1
> > + * or static allocation.
> > + */
> > +#define XENMEMF_force_heap_alloc  (1<<19)
> >   #endif
> If this is for populate_physmap only, then other sub-ops need to reject
> its use.
>
> I have to admit I'm a little wary of allocating another flag here and ...
>
> > --- a/xen/include/xen/mm.h
> > +++ b/xen/include/xen/mm.h
> > @@ -205,6 +205,8 @@ struct npfec {
> >   #define  MEMF_no_icache_flush (1U<<_MEMF_no_icache_flush)
> >   #define _MEMF_no_scrub    8
> >   #define  MEMF_no_scrub    (1U<<_MEMF_no_scrub)
> > +#define _MEMF_force_heap_alloc 9
> > +#define  MEMF_force_heap_alloc (1U<<_MEMF_force_heap_alloc)
> >   #define _MEMF_node        16
> >   #define  MEMF_node_mask   ((1U << (8 * sizeof(nodeid_t))) - 1)
> >   #define  MEMF_node(n)     ((((n) + 1) & MEMF_node_mask) << _MEMF_node)
> ... here - we don't have that many left. Since other sub-ops aren't
> intended to support this flag, did you consider adding another (perhaps
> even arch-specific) sub-op instead?
While revisiting this comment when trying to come up with a V3, I 
realized adding a sub-op here in the same level as 
XENMEM_populate_physmap will basically duplicate the function 
populate_physmap() with just the "else" (the non-1:1 allocation) part, 
also a similar xc_domain_populate_physmap_exact() & co will be needed 
from the toolstack side to call the new sub-op. So I am having the 
concern of the duplication of code and not sure if I understand you 
correctly. Would you please elaborate a bit more or clarify if I 
understand you correctly? Thanks!
Kind regards,
Henry

> Jan