From mboxrd@z Thu Jan  1 00:00:00 1970
From: Razvan Cojocaru <rcojocaru@bitdefender.com>
Subject: Re: (xen 4.6 unstable) triple fault when execute fxsave
 during the procedure of guest iso install
Date: Wed, 24 Jun 2015 12:25:39 +0300
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To: Fanhenglong <fanhenglong@huawei.com>, "xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Cc: "Liuqiming (John)" <john.liuqiming@huawei.com>, Yanqiangjun <yanqiangjun@huawei.com>, "Huangpeng (Peter)" <peter.huangpeng@huawei.com>, "Hanweidong (Randy)" <hanweidong@huawei.com>
List-Id: xen-devel@lists.xenproject.org

On 06/24/2015 12:14 PM, Fanhenglong wrote:
> I want to debug the procedure of windows os install with windbg,
> 
> windbg executes instruction(fxsave) after the blank vm is started and
> before guest iso start to install,
> 
> fxsave trigger the following code path:
> vmx_vmexit_handler(EXIT_REASON_EPT_VIOLATION)
> ->ept_handle_violation
> ->hvm_hap_nested_page_fault
> ->handle_mmio_with_translation
> ->handle_mmio
> ->hvm_emulate_one
> ->x86_emulate
> 
> *X86_emulate return X86EMUL_UNHANDLEABLE*

How are you using Xen in this case? Are you by any chance using the
vm_event system in a way that sends back an "emulate" vm_event response
from userspace?

You might want to look at x86_emulate() in
xen/arch/x86/x86_emulate/x86_emulate.c and see if (and how) fxsave is
being handled.


HTH,
Razvan