HYBRID: set_page_prot() (make pte readonly)

HYBRID: set_page_prot() (make pte readonly)

[Mukesh Rathor]

Hi Jeremy,

This for my hybrid, PV in HVM container with EPT. With EPT, I don't
have the guest going to xen for any va_mapping, and only dealing with
pfn's.

So, I'm at a loss on how to make set_page_prot() work during 
xen_map_identity_early(). I tried few things, but no luck. The fixmap
is not setup during this time, so can't use that. 

Have any ideas?

thanks,
Mukesh

Re: HYBRID: set_page_prot() (make pte readonly)

[Ian Campbell]

On Fri, 2011-10-07 at 03:12 +0100, Mukesh Rathor wrote:
> Hi Jeremy,
> 
> This for my hybrid, PV in HVM container with EPT.

Do you have something functional without EPT? I appreciate that this is
just a stepping stone to the final functionality but it might be worth
starting to post those patches? It would be a useful baseline for others
to start looking at additional features/optimisations on top of etc.

>  With EPT, I don't
> have the guest going to xen for any va_mapping, and only dealing with
> pfn's.

Do you do this by stubbing out the hypercalls (e.g. via a VDSO type
thing in guest address space) or are you cutting off the PV MMU stuff at
start of day using XENFEAT_autotranslated_physmap and/or
XENFEAT_writeable_*? Or some other option?

> So, I'm at a loss on how to make set_page_prot() work during 
> xen_map_identity_early(). I tried few things, but no luck. The fixmap
> is not setup during this time, so can't use that. 

You can just omit it altogether if XENFEAT_writeable_pagetables is set?

Ian.

> 
> Have any ideas?
> 
> thanks,
> Mukesh
> 
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> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel

Re: HYBRID: set_page_prot() (make pte readonly)

[Mukesh Rathor]

On Fri, 7 Oct 2011 08:58:09 +0100
Ian Campbell <Ian.Campbell@citrix.com> wrote:

> Do you have something functional without EPT? I appreciate that this
> is just a stepping stone to the final functionality but it might be
> worth starting to post those patches? It would be a useful baseline
> for others to start looking at additional features/optimisations on
> top of etc.

Hi Ian,

Please see my previous posts with patches attached for hybrid without
EPT. Search for HYBRID in subject.

> Do you do this by stubbing out the hypercalls (e.g. via a VDSO type
> thing in guest address space) or are you cutting off the PV MMU stuff
> at start of day using XENFEAT_autotranslated_physmap and/or
> XENFEAT_writeable_*? Or some other option?

I'm cutting off PV MMU stuff with XENFEAT_auto_translated_physmap.

> > So, I'm at a loss on how to make set_page_prot() work during 
> > xen_map_identity_early(). I tried few things, but no luck. The
> > fixmap is not setup during this time, so can't use that. 
> 
> You can just omit it altogether if XENFEAT_writeable_pagetables is
> set?

Right. 

thanks,
Mukesh

Re: HYBRID: set_page_prot() (make pte readonly)

[Ian Campbell]

On Fri, 2011-10-07 at 18:55 +0100, Mukesh Rathor wrote:
> On Fri, 7 Oct 2011 08:58:09 +0100
> Ian Campbell <Ian.Campbell@citrix.com> wrote:
> 
> > Do you have something functional without EPT? I appreciate that this
> > is just a stepping stone to the final functionality but it might be
> > worth starting to post those patches? It would be a useful baseline
> > for others to start looking at additional features/optimisations on
> > top of etc.
> 
> Hi Ian,
> 
> Please see my previous posts with patches attached for hybrid without
> EPT. Search for HYBRID in subject.

I remember the WIP diffs from back in July, have there been others since
then? I guess I was thinking more along the lines of beginning to post
this new feature as a patch series for review or something like that.

Ian.

Re: HYBRID: set_page_prot() (make pte readonly)

[Mukesh Rathor]

On Fri, 7 Oct 2011 19:23:00 +0100
Ian Campbell <Ian.Campbell@citrix.com> wrote:

> On Fri, 2011-10-07 at 18:55 +0100, Mukesh Rathor wrote:
> > On Fri, 7 Oct 2011 08:58:09 +0100
> > Ian Campbell <Ian.Campbell@citrix.com> wrote:
> > 
> > > Do you have something functional without EPT? I appreciate that
> > > this is just a stepping stone to the final functionality but it
> > > might be worth starting to post those patches? It would be a
> > > useful baseline for others to start looking at additional
> > > features/optimisations on top of etc.
> > 
> > Hi Ian,
> > 
> > Please see my previous posts with patches attached for hybrid
> > without EPT. Search for HYBRID in subject.
> 
> I remember the WIP diffs from back in July, have there been others
> since then? I guess I was thinking more along the lines of beginning
> to post this new feature as a patch series for review or something
> like that.

No, I'm just doing the prototype which allows me to learn the stuff at
the same time. Once I've my prototype working, I'll post patches and be
able to understand comments/feedback better.

Mukesh

Re: HYBRID: set_page_prot() (make pte readonly)

[Ian Campbell]

On Fri, 2011-10-07 at 19:31 +0100, Mukesh Rathor wrote:
> On Fri, 7 Oct 2011 19:23:00 +0100
> Ian Campbell <Ian.Campbell@citrix.com> wrote:
> 
> > On Fri, 2011-10-07 at 18:55 +0100, Mukesh Rathor wrote:
> > > On Fri, 7 Oct 2011 08:58:09 +0100
> > > Ian Campbell <Ian.Campbell@citrix.com> wrote:
> > > 
> > > > Do you have something functional without EPT? I appreciate that
> > > > this is just a stepping stone to the final functionality but it
> > > > might be worth starting to post those patches? It would be a
> > > > useful baseline for others to start looking at additional
> > > > features/optimisations on top of etc.
> > > 
> > > Hi Ian,
> > > 
> > > Please see my previous posts with patches attached for hybrid
> > > without EPT. Search for HYBRID in subject.
> > 
> > I remember the WIP diffs from back in July, have there been others
> > since then? I guess I was thinking more along the lines of beginning
> > to post this new feature as a patch series for review or something
> > like that.
> 
> No, I'm just doing the prototype which allows me to learn the stuff at
> the same time. Once I've my prototype working, I'll post patches and be
> able to understand comments/feedback better.

OK, thanks!

Ian.

Re: HYBRID: set_page_prot() (make pte readonly)

[Jeremy Fitzhardinge]

On 10/06/2011 07:12 PM, Mukesh Rathor wrote:
> So, I'm at a loss on how to make set_page_prot() work during 
> xen_map_identity_early(). I tried few things, but no luck. The fixmap
> is not setup during this time, so can't use that. 
>
> Have any ideas?

Why do you need set_page_prot() at all?  It's only being used to mark
pagetable entries RO, but you presumably don't need to do that with EPT.

    J

Re: HYBRID: set_page_prot() (make pte readonly)

[Mukesh Rathor]

On Fri, 07 Oct 2011 08:46:52 -0700
Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> On 10/06/2011 07:12 PM, Mukesh Rathor wrote:
> > So, I'm at a loss on how to make set_page_prot() work during 
> > xen_map_identity_early(). I tried few things, but no luck. The
> > fixmap is not setup during this time, so can't use that. 
> >
> > Have any ideas?
> 
> Why do you need set_page_prot() at all?  It's only being used to mark
> pagetable entries RO, but you presumably don't need to do that with
> EPT.
> 
>     J

Yes, you are right, with EPT I wouldn't need to do that.

thanks
Mukesh