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[4.17?] Re: [PATCH] common: map_vcpu_info() wants to unshare the underlying page
- To: Henry Wang <Henry.Wang@xxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 25 Oct 2022 18:07:03 +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>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Delivery-date: Tue, 25 Oct 2022 16:07:10 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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.
Jan
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