Re: [Qemu-devel] [PATCH] walk_pml4e(): fix abort on bad PML4E/PDPTE/PDE/PTE addresses

[Luiz Capitulino <lcapitulino@redhat.com>]

On Thu, 30 May 2013 16:22:32 +0200
Andreas Färber <afaerber@suse.de> wrote:

> Am 30.05.2013 16:14, schrieb Luiz Capitulino:
> > On Thu, 30 May 2013 16:10:28 +0200
> > Andreas Färber <afaerber@suse.de> wrote:
> > 
> >> Am 30.05.2013 15:16, schrieb Luiz Capitulino:
> >>> On Thu, 30 May 2013 15:16:18 +0200
> >>> Laszlo Ersek <lersek@redhat.com> wrote:
> >>>
> >>>> On 05/30/13 14:59, Luiz Capitulino wrote:
> >>>>> On Tue, 28 May 2013 14:19:22 -0400
> >>>>> Luiz Capitulino <lcapitulino@redhat.com> wrote:
> >>>>>
> >>>>>> The code used to walk IA-32e page-tables, and possibly PAE page-tables,
> >>>>>> uses the bit mask ~0xfff to get the next PML4E/PDPTE/PDE/PTE address.
> >>>>>>
> >>>>>> However, as we use a uint64_t to store the resulting address, that mask
> >>>>>> gets expanded to 0xfffffffffffff000 which not only ends up selecting
> >>>>>> reserved bits but also selects the XD bit (execute-disable) which
> >>>>>> happens to be enabled by Windows 8, causing qemu_get_ram_ptr() to abort.
> >>>>>>
> >>>>>> This commit fixes that problem by replacing ~0xfff by a correct mask
> >>>>>> that only selects the address bit range (ie. bits 51:12).
> >>>>>>
> >>>>>> Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
> >>>>>
> >>>>> Ping? Wen?
> >>>>>
> >>>>> Would be nice get a Reviewed-by before merging...
> >>>>
> >>>> I didn't miss your submission and did find it OK, I just felt unsure
> >>>> about stating so, because "simple" patches like this are prime territory
> >>>> to burn someone's R-b's worth (ie. to expose a reviewer's lack of
> >>>> information / experience). But hey, what can I lose? The patch does look
> >>>> good to me, so
> >>>
> >>> Thank you Laszlo! It's also new territory for me, that's why I'm asking
> >>> for reviews (otherwise I'd just sneak it in some pull request :-)
> >>
> >> Luiz, you aware aware that I have another fix by Nuohan queued that
> >> seemed orthogonal?
> > 
> > Yes, they should be orthogonal.
> > 
> >> If someone reviews my refactoring series (which
> >> resent that patch) I would like to send out a PULL for that rather soon,
> >> since it blocks further CPU work. I would then include your fix as well
> >> to avoid merge conflicts.
> > 
> > Thanks, although I was going to include it in my tomorrow's QMP pull
> > request. Will this disturb your work?
> 
> I hope not - could you then please pick up Nuohan's bugfix as well?

Sure.

> Still I'd be interested in your review - and I have one more patch to
> add that I created offline yesterday wrt first paging-enabled CPU.

You can CC me.