Re: [Xen-devel] arm64: Approach for DT based NUMA and issues

[Julien Grall <julien.grall@xxxxxxx>]

Hi Vijay,

On 28/11/16 15:05, Vijay Kilari wrote:
> On Mon, Nov 28, 2016 at 7:20 PM, Andre Przywara <andre.przywara@xxxxxxx> wrote:
> > On 26/11/16 06:59, Vijay Kilari wrote:
> >
> > > 3) Parsing Memory nodes:
> > > --------------------------------------
> > > For all the DT memory nodes in the flattend DT, start address, size
> > > and numa-node-id value is extracted and stored in "node_memblk_range[]"
> > > which is of type struct node.
> > >
> > > Each bootinfo.mem entry from UEFI is verified against node_memblk_range[] and
> > > NODE_DATA is populated with start PFN, end PFN and nodeid.
> > >
> > > Populating memnodemap:
> > >
> > > The memnodemap[] is allocated from heap and using the NODE_DATA structure,
> > > the memnodemap[] is populated with nodeid for each page index.
> > >
> > > This memnodemap info is used to fetch memory node id for a given page
> > > by calling phys_to_nid() by memory allocator.
> > >
> > > ISSUE: phys_to_nid() is called by memory allocator before memnodemap[]
> > > is initialized.
> > >
> > > Since memnodemap[] is allocated from heap, and hence boot allocator should
> > > be initialized. The boot_allocator() needs phys_to_nid() which is not
> > > available untill memnodemap[] is initialized. So there is deadlock situation
> > > during initialization. To overcome this phsy_to_nid() should rely on
> > > node_memblk_range[] to get nodeid untill memnodemap[] is initialized.
> > What about having an early boot fallback: like:
> >
> > nodeid_t phys_to_nid(paddr_t addr)
> > {
> >         if (!memnodemap)
> >                 return 0;
> >         ....
> > }
> The memory allocator has all the nodes memory from bootinfo.mem
> So, memory allocator fails when phys_to_nid() returns 0 for node 1 memory.
Why don't you allocate memory using the early boot allocator (see 
alloc_boot_pages) as it is done on x86 (see xen/arch/x86/numa.c)?
Regards,

--
Julien Grall

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