linux-kernel - Re: [PATCH 15/18] KVM: MMU: Propagate the right fault back to the guest after gva_to

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Date:	Mon, 15 Mar 2010 10:41:09 +0100
From:	Joerg Roedel <joro@...tes.org>
To:	Avi Kivity <avi@...hat.com>
Cc:	Joerg Roedel <joerg.roedel@....com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Alexander Graf <agraf@...e.de>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 15/18] KVM: MMU: Propagate the right fault back to the
	guest after gva_to_gpa

On Mon, Mar 15, 2010 at 11:23:07AM +0200, Avi Kivity wrote:
> On 03/15/2010 11:06 AM, Joerg Roedel wrote:
>> On Mon, Mar 15, 2010 at 09:36:52AM +0200, Avi Kivity wrote:
>>    
>>> On 03/03/2010 09:12 PM, Joerg Roedel wrote:
>>>      
>>>> This patch implements logic to make sure that either a
>>>> page-fault/page-fault-vmexit or a nested-page-fault-vmexit
>>>> is propagated back to the guest.
>>>>
>>>> Signed-off-by: Joerg Roedel<joerg.roedel@....com>
>>>> ---
>>>>    arch/x86/kvm/mmu.h         |    1 +
>>>>    arch/x86/kvm/paging_tmpl.h |    2 ++
>>>>    arch/x86/kvm/x86.c         |   15 ++++++++++++++-
>>>>    3 files changed, 17 insertions(+), 1 deletions(-)
>>>>
>>>> diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
>>>> index 64f619b..b42b27e 100644
>>>> --- a/arch/x86/kvm/mmu.h
>>>> +++ b/arch/x86/kvm/mmu.h
>>>> @@ -47,6 +47,7 @@
>>>>    #define PFERR_USER_MASK (1U<<   2)
>>>>    #define PFERR_RSVD_MASK (1U<<   3)
>>>>    #define PFERR_FETCH_MASK (1U<<   4)
>>>> +#define PFERR_NESTED_MASK (1U<<   31)
>>>>
>>>>        
>>>
>>> Why is this needed?  Queue an ordinary page fault page; the injection
>>> code should check the page fault intercept and #VMEXIT if needed.
>>>      
>> This is needed because we could have a nested page fault or an ordinary
>> page fault which need to be propagated.
>>    
>
> Right.
>
> Why is pio_copy_data() changed?  One would think that it would be an  
> all-or-nothing affair.

It was the only place I found where the PROPAGATE_FAULT value was
checked and actually propagated.

	Joerg

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