Re: [Xen-users] svm.c:83:d917 Bad instruction length 0

To:	"James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Subject:	Re: [Xen-users] svm.c:83:d917 Bad instruction length 0
From:	"Trolle Selander" <trolle.selander@xxxxxxxxx>
Date:	Mon, 4 Aug 2008 12:30:40 +0100
Cc:	xen-users <xen-users@xxxxxxxxxxxxxxxxxxx>
Delivery-date:	Mon, 04 Aug 2008 04:31:19 -0700
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In 3.2.2-rc2-pre, an instruction length of 0 doesn't cause a guest crash, but rather a retry of the instruction. This was introduced in cs 16898.
That said, in 3.2 and older svm.c has a bunch of special case emulation code for system instructions, some of which is quite incomplete/incorrect. 3.3 will be much improved in this regard. In any case, a dump of the instruction bytes surrounding the eip would be necessary to determine what the cause was in this particular case.

On Mon, Aug 4, 2008 at 1:54 AM, James Harper <james.harper@xxxxxxxxxxxxxxxx> wrote:

Does anyone know what a 'svm.c:83:d917 Bad instruction length 0' crash
is? It's what I'm getting when trying to use Windows 2008. I finally got
it installed but it is still crashing randomly with that error. Xen is
3.2.1-2 from Debian Lenny, running on an amd64 system. Windows 3008 is
32 bit.

Thanks

James

(XEN) svm.c:83:d917 Bad instruction length 0
(XEN) domain_crash called from svm.c:84
(XEN) Domain 917 (vcpu#0) crashed on cpu#1:
(XEN) ----[ Xen-3.2-1 x86_64 debug=n Not tainted ]----
(XEN) CPU: 1
(XEN) RIP: 001b:[<000000007302affa>]
(XEN) RFLAGS: 0000000000000246 CONTEXT: hvm
(XEN) rax: 0000000000040f33 rbx: 0000000000000800 rcx:
0000000000002001
(XEN) rdx: 000000000789fbff rsi: 000000007302af84 rdi:
0000000000000002
(XEN) rbp: 0000000000a3f624 rsp: 0000000000a3f604 r8:
0000000000000000
(XEN) r9: 0000000000000000 r10: 0000000000000000 r11:
0000000000000000
(XEN) r12: 0000000000000000 r13: 0000000000000000 r14:
0000000000000000
(XEN) r15: 0000000000000000 cr0: 000000008001003b cr4:
00000000000006b9
(XEN) cr3: 000000001f834280 cr2: 00000000730953bc
(XEN) ds: 0023 es: 0023 fs: 003b gs: 0000 ss: 0023 cs: 001b

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Re: [Xen-users] svm.c:83:d917 Bad instruction length 0