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Re: [Xen-devel] [PATCH 3/3] memory: restrict XENMEM_remove_from_physmap to translated guests


  • To: Jan Beulich <JBeulich@xxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Juergen Gross <jgross@xxxxxxxx>
  • Date: Tue, 5 Mar 2019 14:53:25 +0100
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  • Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wei.liu2@xxxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>, Tim Deegan <tim@xxxxxxx>, Julien Grall <julien.grall@xxxxxxx>
  • Delivery-date: Tue, 05 Mar 2019 13:53:34 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Openpgp: preference=signencrypt

On 05/03/2019 14:28, Jan Beulich wrote:
> The commit re-introducing it (14eb3b41d0 ["xen: reinstate previously
> unused XENMEM_remove_from_physmap hypercall"]) as well as the one having
> originally introduced it (d818f3cb7c ["hvm: Use main memory for video
> memory"]) and the one then purging it again (78c3097e4f ["Remove unused
> XENMEM_remove_from_physmap"]) make clear that this operation is intended
> for use on HVM (i.e. translated) guests only. Restrict it at least as
> much, because for PV guests documentation (in the public header) does
> not even match the implementation: It talks about GPFN as input, but
> get_page_from_gfn() assumes a GMFN in the non-translated case (and hands
> back the value passed in).
> 
> Also lift the check in XENMEM_add_to_physmap{,_batch} handling up
> directly into top level hypercall handling, and clarify things in the
> public header accordingly.
> 
> Take the liberty and also replace a pointless use of "current" with a
> more efficient use of an existing local variable (or function parameter
> to be precise).
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Do I read this correctly: nothing bad for the host can happen without
this patch? If this is correct I'd like to defer this patch until 4.13.


Juergen

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