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Re: [PATCH] common: map_vcpu_info() wants to unshare the underlying page
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Date: Tue, 25 Oct 2022 18:17:46 +0200
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
- Delivery-date: Tue, 25 Oct 2022 16:18:14 +0000
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- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On Tue, Oct 25, 2022 at 06:04:49PM +0200, Jan Beulich wrote:
> On 25.10.2022 17:42, Roger Pau Monné wrote:
> > On Tue, Oct 11, 2022 at 10:48:38AM +0200, Jan Beulich wrote:
> >> --- a/xen/common/domain.c
> >> +++ b/xen/common/domain.c
> >> @@ -1484,7 +1484,7 @@ int map_vcpu_info(struct vcpu *v, unsign
> >> if ( (v != current) && !(v->pause_flags & VPF_down) )
> >> return -EINVAL;
> >>
> >> - page = get_page_from_gfn(d, gfn, NULL, P2M_ALLOC);
> >> + page = get_page_from_gfn(d, gfn, NULL, P2M_UNSHARE);
> >
> > I had to go look up that P2M_UNSHARE implies P2M_ALLOC for the users
> > of the parameter, it would be helpful to add a comment in p2m.h that
> > UNSHARE implies ALLOC.
>
> Same here, plus I needed to further figure out that the same implication
> missing on Arm is okay merely because they ignore the respective argument.
... it's made worse by some callers using P2M_ALLOC | P2M_UNSHARE
which adds to the confusion.
Thanks, Roger.
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