Re: [Xen-ia64-devel] [PATCH] Use saner dom0 memory and vcpu defaults, don't panic on over-allocation

[Alex Williamson <alex.williamson@xxxxxx>]

On Fri, 2007-08-03 at 11:09 -0400, Jarod Wilson wrote:
> >>> Indeed, on my 16GB system, only 8MB less from the v2 incantation, and
> >>> the dom0_mem=0 option does properly allocate all available memory to
> >>> dom0. I'm quite happy with this version if everyone else is...
> >> Eep! I retract my happiness... Seems with all memory allocated like
> >> this, I can't get a guest to actually boot. I get this when I try to
> >> bring one up via xm create:

   It's still not completely happy on my 96G system.  If I specify
dom0_mem=0, dom0 fails to startup.  It's incredibly close to the right
value though.  The max calculated memory is:

(XEN) Maximum permitted dom0 size: 97841MB

This fails just before launching dom0 with this:

(XEN) Domain0 EFI passthrough: ACPI 2.0=0x3fdda000 SMBIOS=0x3e52a000
(XEN) assign_new_domain_page: Can't alloc!!!! Aaaargh!
(XEN) 
(XEN) ****************************************
(XEN) Panic on CPU 0:
(XEN) assign_new_domain0_page: can't allocate page for 
dom0****************************************

If I reduce this slightly and boot with dom0_mem=97840MB, dom0 starts to
boot, then hits this:

CPU 1: synchronized ITC with CPU 0 (last diff -2 cycles, maxerr 154 cycles)
CPU 2: synchronized ITC with CPU 0 (last diff -8 cycles, maxerr 159 cycles)
CPU 3: synchronized ITC with CPU 0 (last diff -7 cycles, maxerr 159 cycles)
Brought up 4 CPUs
Total of 4 processors activated (12753.30 BogoMIPS).
migration_cost=11839
(XEN) mm.c:520:d0 Warning: UC to WB for mpaddr=3e52a010
DMI 2.3 present.
NET: Registered protocol family 16
ACPI: bus type pci registered
ACPI: Interpreter enabled
ACPI: Using IOSAPIC for interrupt routing
ACPI: PCI Root Bridge [L000] (0000:00)
(XEN) __assign_domain_page:871 WARNING can't assign page domain 
0xf000000007c18080 id 0
(XEN)   already assigned pte_val 0x6400000000000000
(XEN)   mpaddr 0x00000800bc000000 physaddr 0x00000800bc000000 flags 0x2
(XEN) __assign_domain_page:871 WARNING can't assign page domain 
0xf000000007c18080 id 0
(XEN)   already assigned pte_val 0xf000000000000000
(XEN)   mpaddr 0x00000800bc004000 physaddr 0x00000800bc004000 flags 0x2
(XEN) __assign_domain_page:871 WARNING can't assign page domain 
0xf000000007c18080 id 0
(XEN)   already assigned pte_val 0xf000ff54f0000000
(XEN)   mpaddr 0x00000800bc008000 physaddr 0x00000800bc008000 flags 0x2
...

To get it to boot all the way to userspace, I had to reduce dom0's
memory a full 16MB further, down to dom0_mem=97824M.  Each few MB more
kept for Xen allowed the boot to enumerate another PCI root bridge.  I
suspect it's the ioremaps going on there that are eating up free heap
pages.  Maybe this also suggests that xen doesn't really know how much
dynamic memory it might take to boot dom0 all the way.  Thanks,

        Alex

-- 
Alex Williamson                             HP Open Source & Linux Org.


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