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xen-devel
[Xen-devel] Re: [PATCH][RFC] Emulating real mode with x86_emulate
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To: |
"Kamble, Nitin A" <nitin.a.kamble@xxxxxxxxx> |
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Subject: |
[Xen-devel] Re: [PATCH][RFC] Emulating real mode with x86_emulate |
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From: |
Anthony Liguori <aliguori@xxxxxxxxxx> |
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Date: |
Mon, 02 Apr 2007 13:54:05 -0500 |
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"Yu, Wilfred" <wilfred.yu@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Keir Fraser <keir@xxxxxxxxxxxxx>, "Nakajima, Jun" <jun.nakajima@xxxxxxxxx> |
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Mon, 02 Apr 2007 11:53:05 -0700 |
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Kamble, Nitin A wrote:
On Fri, 2007-03-30 at 15:11 -0700, Anthony Liguori wrote:
set_cr0 is returning 1 though which should increment eip to the next
instruction.
I'm a bit perplexed about my eip now and also why your eip is still 0.
It should be the instruction following the mov cr0.
Regards,
Anthony Liguori
Hi Anthony,
I don't see any code doing context save/restore like
vmx_world_save , vmx_world_restore in the current code for the
hyperviser based emulator.
Before calling x86_emulate, we use hvm_store_cpu_guest_regs() to copy
the guest state into a regs struct (which happens to be the vcpu's reg
struct). This reads directly from the VMCS via vmread() so it should be
okay. I don't think a vmx_world_save/restore is actually needed
although perhaps I'm missing something?
Also the function arch_vmx_do_resume() is called at the time of vcpu
schedule, so it is not right to call the vmx_do_emulate() from there.
Right, the idea was to have x86_emulate() be called instead of
vmentry(). I thought that being in the set_cr0 path would ensure that
we go through do_resume() again. Is this assumption incorrect?
I didn't want to just stick it in the set_cr0 path because we ought to
be able to pull the emulation loop into common code for SVM/VT and the
do_resume path seems like the only place where there's common place to
hook right now.
Regards,
Anthony Liguori
The code would need vmx_world_save/restore in the code path before
returning to vmx_asm_vmexit_handler from vmx_vmexit_handler.
Without that I don't see it can emulate any instructions.
Thanks & Regards,
Nitin
Open Source Technology Center, Intel Corporation.
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