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From: Marek Olszewski <mareko@csail.mit.edu>
To: Avi Kivity <avi@redhat.com>
Cc: kvm@vger.kernel.org
Subject: Re: KVM Page Fault Question
Date: Fri, 02 Apr 2010 00:41:58 -0400	[thread overview]
Message-ID: <4BB57596.6090109@csail.mit.edu> (raw)
In-Reply-To: <4BA33833.8060703@redhat.com>

When a guest OS writes to a shadowed (and therefore page protected) 
guest page table, does the resulting page fault get handled in 
paging_tmpl.h:xxx_page_fault or does it call some rmap related code 
directly?  Also, what does the "direct" mmu page role mean?

Thanks!

Marek


Avi Kivity wrote:
> On 03/19/2010 01:50 AM, Marek Olszewski wrote:
>> When using VMX without EPT, is it ever possible for a guest to 
>> receive a page fault without it first appearing (and being 
>> reinjected) in KVM? 
>
> Yes.  On Intel hosts only, and controlled by bypass_guest_pf.
>
>> I'm seeing some strange behavior where accesses to mprotected (but 
>> yet to be accessed) memory causes a fault in the guest OS, that I 
>> cannot see KVM intercepting.
>>
>
> Look for 'shadow_trap_nonpresent_pte' (which will trap into kvm) and 
> 'shadow_notrap_nonpresent_pte' (which will not) in the code.
>


  reply	other threads:[~2010-04-02  4:42 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-03-10  4:57 Shadow page table questions Marek Olszewski
2010-03-10  9:47 ` Avi Kivity
2010-03-11  0:06   ` Marek Olszewski
2010-03-11  6:39     ` Avi Kivity
2010-03-11 16:14       ` Marek Olszewski
2010-03-13  8:51         ` Avi Kivity
2010-03-18 23:50           ` KVM Page Fault Question Marek Olszewski
2010-03-19  8:39             ` Avi Kivity
2010-04-02  4:41               ` Marek Olszewski [this message]
2010-04-02  6:39                 ` Avi Kivity
     [not found]                   ` <4BB614BC.9080608@csail.mit.edu>
2010-04-04 16:59                     ` Avi Kivity
2010-04-22  5:26                       ` Marek Olszewski
2010-04-22  6:52                         ` Avi Kivity
     [not found]                           ` <4BD0DFBE.1090103@csail.mit.edu>
2010-04-26  5:42                             ` Marek Olszewski
2010-05-20  2:24                           ` Shadow MMU state preserved across kvm_mmu_zap_all? Marek Olszewski

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