Re: [Xen-devel] machine address

[HANNAS YAYA Issa <issa.hannasyaya@xxxxxxxxxxx>]

Ok. thank you
On Tue, 31 Mar 2015 10:26:06 +0100, George Dunlap wrote:
> On Mon, Mar 30, 2015 at 3:00 PM, HANNAS YAYA Issa
> <issa.hannasyaya@xxxxxxxxxxx> wrote:
> > Hi
> > When there is a page fault the trapper of the page fault in the 
> > hypervisor
> > is do_page_fault in xen/arch/x86/traps.c right?
> That's for PV guests.  For HVM guests, the page fault causes a 
> VMEXIT,
> which will be handled in
> xen/arch/x86/hvm/vmx/vmx.c:vmx_vmexit_handler()  (on Intel).
>
> > in this funcion i found a method read_cr2() which return the virtual 
> > adrress
> > of the page who generate the page fault.
> > My question is : is it possible to get the machine address of the 
> > page table
> > entry for this virtual address?
> In general the way you have to do that is to use the virtual address
> to walk the guest's pagetables (exactly the same way the hardware
> would do on a TLB miss).
>
> For HVM guests (or PV guests in shadow mode) there's already code to
> do walk for you in xen/arch/x86/mm/guest_walk.c:guest_walk().  You 
> can
> see how it's called from the HAP code and the shadow code if you 
> want.
> I don't immediately see a walker for PV guests.
>
>  -George

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