linux-kernel - Re: [kvm-devel] [PATCH 2/3] Refactor hypercall infrastructure (v3)

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Message-ID: <46EFD318.3070401@codemonkey.ws>
Date:	Tue, 18 Sep 2007 08:31:04 -0500
From:	Anthony Liguori <anthony@...emonkey.ws>
To:	Avi Kivity <avi@...ranet.com>
CC:	Anthony Liguori <aliguori@...ibm.com>,
	kvm-devel@...ts.sourceforge.net, Zachary Amsden <zach@...are.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [kvm-devel] [PATCH 2/3] Refactor hypercall infrastructure (v3)

Avi Kivity wrote:
> Avi Kivity wrote:
>   
>> Avi Kivity wrote:
>>     
>>> Anthony Liguori wrote:
>>>  
>>>       
>>>> This patch refactors the current hypercall infrastructure to better 
>>>> support live
>>>> migration and SMP.  It eliminates the hypercall page by trapping the UD
>>>> exception that would occur if you used the wrong hypercall 
>>>> instruction for the
>>>> underlying architecture and replacing it with the right one lazily.
>>>>
>>>> It also introduces the infrastructure to probe for hypercall 
>>>> available via
>>>> CPUID leaves 0x40000000.  CPUID leaf 0x40000001 should be filled out by
>>>> userspace.
>>>>
>>>> A fall-out of this patch is that the unhandled hypercalls no longer 
>>>> trap to
>>>> userspace.  There is very little reason though to use a hypercall to 
>>>> communicate
>>>> with userspace as PIO or MMIO can be used.  There is no code in tree 
>>>> that uses
>>>> userspace hypercalls.
>>>>
>>>>       
>>>>         
>>> Surprisingly, this patch kills Windows XP (ACPI HAL).  I'll try to 
>>> find out why.
>>>
>>>   
>>>       
>> Not trapping #UD brings things back to normal.  So, Windows likes to 
>> execute undefined instructions, and we don'd handle these well.
>>
>>     
> Okay, vmx_inject_ud() was broken.  Fixed now.
>   

Yeah, I was just about to send the patch for that.  Sorry about that, I 
didn't even think to test Windows...

Regards,

Anthony Liguori

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