Re: [Xen-devel] [PATCH] Boot PV guests with more than 128GB (v2) for 3.7

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, Aug 02, 2012 at 10:05:27AM +0100, Jan Beulich wrote:
> >>> On 01.08.12 at 17:50, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> 
> >>> wrote:
> > With these patches I've gotten it to boot up to 384GB. Around that area
> > something weird happens - mainly the pagetables that the toolstack allocated
> > seems to have missing data. I hadn't looked in details, but this is what
> > domain builder tells me:
> > 
> > 
> > xc_dom_alloc_segment:   ramdisk      : 0xffffffff82278000 -> 
> > 0xffffffff930b4000  (pfn 0x2278 + 0x10e3c pages)
> > xc_dom_malloc            : 1621 kB
> > xc_dom_pfn_to_ptr: domU mapping: pfn 0x2278+0x10e3c at 0x7fb0853a2000
> > xc_dom_do_gunzip: unzip ok, 0x4ba831c -> 0x10e3be10
> > xc_dom_alloc_segment:   phys2mach    : 0xffffffff930b4000 -> 
> > 0xffffffffc30b4000  (pfn 0x130b4 + 0x30000 pages)
> > xc_dom_malloc            : 4608 kB
> > xc_dom_pfn_to_ptr: domU mapping: pfn 0x130b4+0x30000 at 0x7fb0553a2000
> > xc_dom_alloc_page   :   start info   : 0xffffffffc30b4000 (pfn 0x430b4)
> > xc_dom_alloc_page   :   xenstore     : 0xffffffffc30b5000 (pfn 0x430b5)
> > xc_dom_alloc_page   :   console      : 0xffffffffc30b6000 (pfn 0x430b6)
> > nr_page_tables: 0x0000ffffffffffff/48: 0xffff000000000000 -> 
> > 0xffffffffffffffff, 1 table(s)
> > nr_page_tables: 0x0000007fffffffff/39: 0xffffff8000000000 -> 
> > 0xffffffffffffffff, 1 table(s)
> > nr_page_tables: 0x000000003fffffff/30: 0xffffffff80000000 -> 
> > 0xffffffffffffffff, 2 table(s)
> > nr_page_tables: 0x00000000001fffff/21: 0xffffffff80000000 -> 
> > 0xffffffffc33fffff, 538 table(s)
> > xc_dom_alloc_segment:   page tables  : 0xffffffffc30b7000 -> 
> > 0xffffffffc32d5000  (pfn 0x430b7 + 0x21e pages)
> > xc_dom_pfn_to_ptr: domU mapping: pfn 0x430b7+0x21e at 0x7fb055184000
> > xc_dom_alloc_page   :   boot stack   : 0xffffffffc32d5000 (pfn 0x432d5)
> > xc_dom_build_image  : virt_alloc_end : 0xffffffffc32d6000
> > xc_dom_build_image  : virt_pgtab_end : 0xffffffffc3400000
> > 
> > Note it is is 0xffffffffc30b4000 - so already past the level2_kernel_pgt 
> > (L3[510]
> > and in level2_fixmap_pgt territory (L3[511]).
> > 
> > At that stage we are still operating using the Xen provided pagetable - 
> > which
> > look to have the L4[511][511] empty! Which sounds to me like a Xen 
> > tool-stack
> > problem? Jan, have you seen something similar to this?
> 
> No we haven't, but I also don't think anyone tried to create as
> big a DomU. I was, however, under the impression that DomU-s
> this big had been created at Oracle before. Or was that only up
> to 256Gb perhaps?

Mukesh do you recall? Was it with OVM2.2.2 which was 3.4 based?
It might be that we did not have the 1TB hardware at that time yet.

Or perhaps I am missing some bug-fix from the old product..

> 
> In any case, setup_pgtables_x86_64() indeed looks flawed
> to me: While the clearing of l1tab looks right, l[23]tab get
> cleared (and hence a new table allocated) too early. l2tab
> should really get cleared only when l1tab gets cleared _and_
> the L2 clearing condition is true. Similarly for l3tab then, and
> of course - even though it would unlikely ever matter -
> setup_pgtables_x86_32_pae() is broken in the same way.
> 
> Afaict this got broken with the domain build re-write between
> 3.0.4 and 3.1 (the old code looks alright).

Oh wow. Long time ago. Thanks for the pointer - will look at this
once I am through with some of the current bug log.
> 
> Jan
> 
> 
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