Re: [Xen-devel] where can I find the 'address translation' code in Xen?

[Petr Tesarik <ptesarik@xxxxxxx>]

Hi Minjun,

On Mon, 30 Apr 2018 17:17:36 +0900
Minjun Hong <nickeysgo@xxxxxxxxx> wrote:

> On Mon, Apr 30, 2018 at 3:44 PM, Petr Tesarik <ptesarik@xxxxxxx> wrote:
> 
> > Hi Minjun,
> >
> > On Sun, 29 Apr 2018 19:11:30 +0900
> > Minjun Hong <nickeysgo@xxxxxxxxx> wrote:
> >  
> > >[...]
> > > My question is,
> > >
> > > 1. Is it sure that the function will be called even though the HW already
> > > translates the address and populates the TLB entry?  
> >
> > I think you miss the point. The hardware page tables for PV domains
> > already contain machine addresses. In other words, virtual addresses
> > get translated directly to machine addresses by the hardware page table
> > walker.
> >  
> > > 2. I'm just asking, is there any code in Xen that is related to the
> > > behavior of the 'hardware walker'?  
> >
> > Not sure what you mean. Maybe this question is no longer pertinent
> > given the explanation above?
> >
> > HTH,
> > Petr T
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxxx
> > https://lists.xenproject.org/mailman/listinfo/xen-devel  
> 
> 
> 
> Thanks for your kind answer, Petr.
> 
> In your answer on my first question, I was wondering why the function (
> guest_walk_tables()) should be called even after the address translation
> and TLB filling has been completed by the hardware page table walker.
> As you mentioned, original goal (address translation) is achieved by the
> hardware. If so, is its role like bottom half of interrupt?

Ah, now I'm starting to get your point. So, you're interested in
what happens after guest page tables are updated.

> I want to know this function is always called after the translation
> by the hardware page walker.

It seems to me that there are quite a few ways to avoid a full page
table walk, but I'm not an expert on this topic, sorry.

Petr T


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