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[Xen-devel] Every page fault caused pagetable walk when using xenoprofil

To: "xen-devel" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] Every page fault caused pagetable walk when using xenoprofile
From: "ZelluX" <zellux@xxxxxx>
Date: Fri, 17 Jul 2009 15:15:43 +0800
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Hi, all

I was measuring some performance with help of xenoprofile 0.9.3 on Xen 3.3.0, and it worked well under direct mode (i.e., no shadow page table enabled)

But when I started Xen with parameter dom0_shadow=1, which enabled shadow page table, the benchmark performance downgraded greatly when xenoprofile was started. What's more, after I checked xm dmesg, I found pagetable walks were triggered several times due to reserved bit in page table:

(XEN) ----[ Xen-3.3.0  x86_64  debug=n  Tainted:    C ]----
(XEN) CPU:    4
(XEN) RIP:    e008:[<ffff828c80152cb6>] __copy_from_user_ll+0x26/0x40
(XEN) RFLAGS: 0000000000010046   CONTEXT: hypervisor
==== BLAH BLAH BLAH ====
(XEN) Xen call trace:
(XEN)    [<ffff828c80152cb6>] __copy_from_user_ll+0x26/0x40
(XEN)    [<ffff828c801a5cba>] xenoprof_backtrace+0xfa/0x440
(XEN)    [<ffff828c8011c105>] xenoprof_log_event+0xe5/0x1b0
(XEN)    [<ffff828c801a584e>] ppro_check_ctrs+0x9e/0x120
(XEN)    [<ffff828c801a47a9>] nmi_callback+0x29/0x80
(XEN)    [<ffff828c8014e518>] do_nmi+0x38/0x100
(XEN)    [<ffff828c801a6877>] handle_ist_exception+0x52/0x5b
(XEN) d0:v10: reserved bit in page table (ec=0009)
(XEN) Pagetable walk from 0000000000402540:
(XEN)  L4[0x000] = 000000056265c067 5555555555555555
(XEN)  L3[0x000] = 000000056212b067 5555555555555555
(XEN)  L2[0x002] = 000000056215d067 5555555555555555
(XEN)  L1[0x002] = ffffffffffffffff ffffffffffffffff

Has any one been confronted by this problem before?

Many thanks for your replies.
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