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Re: [Xen-devel] Fwd: xenbusb_nop_confighook_cb timeout and cd issue

  • To: Christoph Egger <Christoph_Egger@xxxxxx>
  • From: Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>
  • Date: Thu, 17 Jan 2013 15:50:26 +0100
  • Cc: "freebsd-xen@xxxxxxxxxxx" <freebsd-xen@xxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxx>, Egoitz Aurrekoetxea Aurre <egoitz@xxxxxxxxxx>, Steven Chamberlain <steven@xxxxxxxxxxx>
  • Delivery-date: Thu, 17 Jan 2013 14:51:53 +0000
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  • List-id: Xen developer discussion <xen-devel.lists.xen.org>

Am 17.01.2013 15:35, schrieb Christoph Egger:
Am 17.01.2013 12:19, schrieb Steven Chamberlain:

A little more background to this:

An error was first seen on Debian's i386 autobuilders when building Xen
4.1.2 (Debian package 4.1.2-7), but only after a switch from gcc-4.6 to
gcc-4.7 which seems to be what prompted this.  I'm not sure if it would
have affected amd64 builds as we don't have logs for those:

gcc -O2 -fomit-frame-pointer -m32 -march=i686 -fno-strict-aliasing -std=gnu99 
-Wall -Wstrict-prototypes -Wno-unused-value -Wdeclaration-after-statement 
-Wno-unused-but-set-variable  -DNDEBUG -nostdinc -fno-builtin -fno-common 
-Wredundant-decls -iwithprefix include -Werror -Wno-pointer-arith -pipe 
 -msoft-float -fno-stack-protector -fno-exceptions -g -D__XEN__ -MMD -MF 
.i8259.o.d -c i8259.c -o i8259.o
i8259.c:66:9: error: initialization from incompatible pointer type [-Werror]
i8259.c:66:9: error: (near initialization for 'interrupt[0]') [-Werror]
i8259.c:66:9: error: initialization from incompatible pointer type [-Werror]
i8259.c:66:9: error: (near initialization for 'interrupt[1]') [-Werror]
i8259.c:66:9: error: initialization from incompatible pointer type [-Werror]
i8259.c:66:9: error: (near initialization for 'interrupt[2]') [-Werror]

In order to fix the build issue, this patch was written, and is still
used when building Debian's Xen 4.1.3 packages:

Since October 2012 many FreeBSD (9.x) users reported an issue booting on
Xenserver 6.1 / XCP 1.6 (incl. -BETA) but not affecting XCP 1.5:

There were prior reports of identical symptoms triggered by guest CD-ROM
drives without media, but this seems to be an unrelated bug.

Egoitz, who has done a lot of work porting FreeBSD to XCP recently,
found that Debian's (Wheezy) Xen kernel didn't have this bug;  realised
that the above patch fixes it.

I experienced the bug when booting the FreeBSD 9.0 kernel on a NetBSD
6.0.1 dom0 after upgrading to pkgsrc-2012Q4 (Xen 4.1.3, from a binary
package, unsure which compiler was used to build it).  Likewise the
patch fixed the issue for me;  I used gcc 4.5.3.


I compiled a clean checked out xen-4.1-testing.hg with and without the patch.

I created a objdump -S -D  from each xen-syms.
A diff -u between both objdump's shows this:

--- xen-syms-unpatched.objdump  2013-01-17 12:47:25.000000000 +0000
+++ xen-syms-patched.objdump    2013-01-17 12:52:26.000000000 +0000
@@ -1,5 +1,5 @@

-xen-syms-unpatched:     file format elf64-x86-64
+xen-syms-patched:     file format elf64-x86-64

  Disassembly of section .text:

@@ -435776,16 +435776,20 @@ ffff82c480215a03:   20 31
  ffff82c480215a05:      37                      (bad)
  ffff82c480215a06:      20 31                   and    %dh,(%rcx)
  ffff82c480215a08:      32 3a                   xor    (%rdx),%bh
-ffff82c480215a0a:      33 33                   xor    (%rbx),%esi
-ffff82c480215a0c:      3a 33                   cmp    (%rbx),%dh
-ffff82c480215a0e:      35 20 55 54 43          xor    $0x43545520,%eax
-ffff82c480215a13:      20 32                   and    %dh,(%rdx)
+ffff82c480215a0a:      33 30                   xor    (%rax),%esi
+ffff82c480215a0c:      3a 30                   cmp    (%rax),%dh
+ffff82c480215a0e:      39 20                   cmp    %esp,(%rax)
+ffff82c480215a10:      55                      push   %rbp
+ffff82c480215a11:      54                      push   %rsp
+ffff82c480215a12:      43 20 32                rexYZ and    %sil,(%r10)
  ffff82c480215a15:      30 31                   xor    %dh,(%rcx)
  ffff82c480215a17:      33 00                   xor    (%rax),%eax
  ffff82c480215a19:      31 32                   xor    %esi,(%rdx)
  ffff82c480215a1b:      3a 33                   cmp    (%rbx),%dh
-ffff82c480215a1d:      33 3a                   xor    (%rdx),%edi
-ffff82c480215a1f:      33 35 00 63 68 65       xor    1701339904(%rip),%esi        # 
+ffff82c480215a1d:      30 3a                   xor    %bh,(%rdx)
+ffff82c480215a1f:      30 39                   xor    %bh,(%rcx)
+ffff82c480215a21:      00 63 68                add    %ah,0x68(%rbx)
+ffff82c480215a24:      65                      gs
  ffff82c480215a25:      67                      addr32
  ffff82c480215a26:      67                      addr32
  ffff82c480215a27:      65                      gs

Are you sure? This looks like different ASCII texts to me:

-"12:33:35 UTC 2013"
+"12:30:39 UTC 2013"

Seems to be related to the time the file was generated.


Juergen Gross                 Principal Developer Operating Systems
PBG PDG ES&S SWE OS6                   Telephone: +49 (0) 89 3222 2967
Fujitsu Technology Solutions              e-mail: juergen.gross@xxxxxxxxxxxxxx
Domagkstr. 28                           Internet: ts.fujitsu.com
D-80807 Muenchen                 Company details: ts.fujitsu.com/imprint.html

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