Re: [PATCH 04/16] x86/srat: vmap the pages for acpi_slit

[Hongyan Xia <hx242@xen.org>]

On Mon, 2020-11-30 at 11:16 +0100, Jan Beulich wrote:
> On 30.04.2020 22:44, Hongyan Xia wrote:
> > --- a/xen/arch/x86/srat.c
> > +++ b/xen/arch/x86/srat.c
> > @@ -196,7 +196,8 @@ void __init acpi_numa_slit_init(struct
> > acpi_table_slit *slit)
> >  		return;
> >  	}
> >  	mfn = alloc_boot_pages(PFN_UP(slit->header.length), 1);
> > -	acpi_slit = mfn_to_virt(mfn_x(mfn));
> > +	acpi_slit = vmap_boot_pages(mfn, PFN_UP(slit->header.length));
> > +	BUG_ON(!acpi_slit);
> >  	memcpy(acpi_slit, slit, slit->header.length);
> >  }
> 
> I'm not sure in how far this series is still to be considered
> active / pending; I still have it in my inbox as something to
> look at in any event. If it is, then I think the latest by this
> patch it becomes clear that we either want to make vmalloc()
> boot-allocator capable, or introduce e.g. vmalloc_boot().
> Having this recurring pattern including the somewhat odd
> vmap_boot_pages() is imo not the best way forward. It would
> then also no longer be necessary to allocate contiguous pages,
> as none of the users up to here appear to have such a need.

This series is blocked on the PTE domheap conversion series so I will
definitely come back here after that series is merged.

vmap_boot_pages() (poorly named, there is nothing "boot" about it) is
actually useful in other patches as well, especially when there is no
direct map but we need to map a contiguous range, since
map_domain_page() can only handle a single one. So I would say there
will be a need for this function (maybe call it vmap_contig_pages()?)
even if for this patch a boot-capable vmalloc can do the job.

Hongyan