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RE: [4.17?] Re: [PATCH] common: map_vcpu_info() wants to unshare the underlying page
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Henry Wang <Henry.Wang@xxxxxxx>
- Date: Wed, 26 Oct 2022 02:03:32 +0000
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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>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>
- Delivery-date: Wed, 26 Oct 2022 02:03:55 +0000
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- Thread-topic: [4.17?] Re: [PATCH] common: map_vcpu_info() wants to unshare the underlying page
(+Arm maintainers)
Hi Jan,
> -----Original Message-----
> From: Jan Beulich <jbeulich@xxxxxxxx>
> Sent: Wednesday, October 26, 2022 12:07 AM
> To: Henry Wang <Henry.Wang@xxxxxxx>
> Cc: 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>; Roger Pau Monné <roger.pau@xxxxxxxxxx>
> Subject: [4.17?] Re: [PATCH] common: map_vcpu_info() wants to unshare
> the underlying page
>
> On 25.10.2022 17:42, Roger Pau Monné wrote:
> > On Tue, Oct 11, 2022 at 10:48:38AM +0200, Jan Beulich wrote:
> >> Not passing P2M_UNSHARE to get_page_from_gfn() means there won't
> even be
> >> an attempt to unshare the referenced page, without any indication to the
> >> caller (e.g. -EAGAIN). Note that guests have no direct control over
> >> which of their pages are shared (or paged out), and hence they have no
> >> way to make sure all on their own that the subsequent obtaining of a
> >> writable type reference can actually succeed.
> >>
> >> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> >
> > Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
>
> I didn't Cc you on the initial submission because mem-sharing isn't a
> supported feature, but upon reconsideration I thought I'd at least ask
> whether you would want to give this a release-ack. I don't really see
> any risk associated with it.
By looking at the patch itself, this change seems ok to me, so I think
I will not block it, but I think Arm maintainers' approval might be needed
because of the discussion in [1], so I added them for their information.
If Arm maintainers do not object the change, you can have my release-ack.
[1]
https://lore.kernel.org/xen-devel/1780acb3-d297-edc6-3a1e-adf8b28a5262@xxxxxxxx/
Kind regards,
Henry
>
> Jan
|
