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5bc6f9888d
linux/arch/x86/xen
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Konrad Rzeszutek Wilk 5bc6f9888d xen/p2m: Reserve 8MB of _brk space for P2M leafs when populating back. 
When we release pages back during bootup:

Freeing  9d-100 pfn range: 99 pages freed
Freeing  9cf36-9d0d2 pfn range: 412 pages freed
Freeing  9f6bd-9f6bf pfn range: 2 pages freed
Freeing  9f714-9f7bf pfn range: 171 pages freed
Freeing  9f7e0-9f7ff pfn range: 31 pages freed
Freeing  9f800-100000 pfn range: 395264 pages freed
Released 395979 pages of unused memory

We then try to populate those pages back. In the P2M tree however
the space for those leafs must be reserved - as such we use extend_brk.
We reserve 8MB of _brk space, which means we can fit over
1048576 PFNs - which is more than we should ever need.

Without this, on certain compilation of the kernel we would hit:

(XEN) domain_crash_sync called from entry.S
(XEN) CPU:    0
(XEN) RIP:    e033:[<ffffffff818aad3b>]
(XEN) RFLAGS: 0000000000000206   EM: 1   CONTEXT: pv guest
(XEN) rax: ffffffff81a7c000   rbx: 000000000000003d   rcx: 0000000000001000
(XEN) rdx: ffffffff81a7b000   rsi: 0000000000001000   rdi: 0000000000001000
(XEN) rbp: ffffffff81801cd8   rsp: ffffffff81801c98   r8:  0000000000100000
(XEN) r9:  ffffffff81a7a000   r10: 0000000000000001   r11: 0000000000000003
(XEN) r12: 0000000000000004   r13: 0000000000000004   r14: 000000000000003d
(XEN) r15: 00000000000001e8   cr0: 000000008005003b   cr4: 00000000000006f0
(XEN) cr3: 0000000125803000   cr2: 0000000000000000
(XEN) ds: 0000   es: 0000   fs: 0000   gs: 0000   ss: e02b   cs: e033
(XEN) Guest stack trace from rsp=ffffffff81801c98:

.. which is extend_brk hitting a BUG_ON.

Interestingly enough, most of the time we are not going to hit this
b/c the _brk space is quite large (v3.5):
 ffffffff81a25000 B __brk_base
 ffffffff81e43000 B __brk_limit
= ~4MB.

vs earlier kernels (with this back-ported), the space is smaller:
 ffffffff81a25000 B __brk_base
 ffffffff81a7b000 B __brk_limit
= 344 kBytes.

where we would certainly hit this and hit extend_brk.

Note that git commit c3d93f8801
(xen: populate correct number of pages when across mem boundary (v2))
exposed this bug).

[v1: Made it 8MB of _brk space instead of 4MB per Jan's suggestion]

CC: stable@vger.kernel.org #only for 3.5
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2012-08-02 10:39:53 -04:00
..
apic.c x86/xen/apic: Add missing #include <xen/xen.h> 2012-05-18 09:34:45 +02:00
debugfs.c debugfs: Add support to print u32 array in debugfs 2012-04-17 00:18:36 -04:00
debugfs.h debugfs: Add support to print u32 array in debugfs 2012-04-17 00:18:36 -04:00
enlighten.c xen PVonHVM: move shared_info to MMIO before kexec 2012-07-19 15:52:05 -04:00
grant-table.c Merge commit 'v3.2-rc3' into stable/for-linus-3.3 2011-12-20 17:01:18 -05:00
irq.c xen: use this_cpu_xxx replace percpu_xxx funcs 2012-01-24 12:20:24 -05:00
Kconfig xen: Make XEN_MAX_DOMAIN_MEMORY have more sensible defaults 2011-11-21 17:14:46 -05:00
Makefile xen/x86: Implement x86_apic_ops 2012-05-01 14:50:33 -04:00
mmu.c xen/mm: zero PTEs for non-present MFNs in the initial page table 2012-07-19 15:51:44 -04:00
mmu.h xen: make a pile of mmu pvop functions static 2011-05-20 14:25:24 -07:00
multicalls.c xen/multicall: move *idx fields to start of mc_buffer 2011-07-18 15:43:46 -07:00
multicalls.h xen: use this_cpu_xxx replace percpu_xxx funcs 2012-01-24 12:20:24 -05:00
p2m.c xen/p2m: Reserve 8MB of _brk space for P2M leafs when populating back. 2012-08-02 10:39:53 -04:00
pci-swiotlb-xen.c X86 & IA64: adapt for dma_map_ops changes 2012-03-28 16:36:31 +02:00
platform-pci-unplug.c xen:pvhvm: Modpost section mismatch fix 2011-07-11 13:37:04 -04:00
setup.c xen: populate correct number of pages when across mem boundary (v2) 2012-07-19 15:52:06 -04:00
smp.c Features: 2012-05-24 16:02:08 -07:00
smp.h xen: implement apic ipi interface 2012-05-07 15:33:15 -04:00
spinlock.c debugfs: Add support to print u32 array in debugfs 2012-04-17 00:18:36 -04:00
suspend.c xen PVonHVM: move shared_info to MMIO before kexec 2012-07-19 15:52:05 -04:00
time.c Merge branch 'upstream/xen-settime' of git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen 2011-11-06 20:15:05 -08:00
trace.c xen/trace: Fix compile error when CONFIG_XEN_PRIVILEGED_GUEST is not set 2011-08-05 09:43:02 -04:00
vdso.h
vga.c xen: allow enable use of VGA console on dom0 2011-06-06 11:46:00 -04:00
xen-asm_32.S x86, extable: Remove open-coded exception table entries in arch/x86/xen/xen-asm_32.S 2012-04-20 13:51:39 -07:00
xen-asm_64.S xen: use iret for return from 64b kernel to 32b usermode 2009-12-03 11:14:54 -08:00
xen-asm.h xen: make direct versions of irq_enable/disable/save/restore to common code 2009-02-04 16:59:04 -08:00
xen-asm.S xen: correctly check for pending events when restoring irq flags 2012-04-27 16:04:21 -04:00
xen-head.S x86, asm: Cleanup unnecssary macros in asm-offsets.c 2011-02-25 16:37:32 -08:00
xen-ops.h xen PVonHVM: move shared_info to MMIO before kexec 2012-07-19 15:52:05 -04:00