Re: [Xen-devel] [PATCH v12 05/11] x86/mm: add HYPERVISOR_memory_op to acquire guest resources

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 20 October 2017 07:25
> To: Julien Grall <julien.grall@xxxxxxxxxx>
> Cc: Julien Grall <julien.grall@xxxxxxx>; Andrew Cooper
> <Andrew.Cooper3@xxxxxxxxxx>; George Dunlap
> <George.Dunlap@xxxxxxxxxx>; Ian Jackson <Ian.Jackson@xxxxxxxxxx>; Paul
> Durrant <Paul.Durrant@xxxxxxxxxx>; Roger Pau Monne
> <roger.pau@xxxxxxxxxx>; Wei Liu <wei.liu2@xxxxxxxxxx>; Stefano Stabellini
> <sstabellini@xxxxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx; Konrad Rzeszutek
> Wilk <konrad.wilk@xxxxxxxxxx>; Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>;
> Tim (Xen.org) <tim@xxxxxxx>
> Subject: Re: [Xen-devel] [PATCH v12 05/11] x86/mm: add
> HYPERVISOR_memory_op to acquire guest resources
> 
> >>> On 19.10.17 at 18:21, <julien.grall@xxxxxxxxxx> wrote:
> > Looking a bit more at the resource you can acquire from this hypercall.
> > Some of them are allocated using alloc_xenheap_page() so not assigned to
> > a domain.
> >
> > So I am not sure how you can expect a function set_foreign_p2m_entry to
> > take reference in that case.
> 
> Hmm, with the domain parameter added, DOMID_XEN there (for
> Xen heap pages) could identify no references to be taken, if that
> was really the intended behavior in that case. However, even for
> Xen heap pages life time tracking ought to be done - it is for a
> reason that share_xen_page_with_guest() assigns the target
> domain as the owner of such pages, as that allows get_page() to
> succeed for them.
> 

So, nothing I'm doing here is making anything worse, right? Grant tables are 
assigned to the guest, and IOREQ server pages are allocated with 
alloc_domheap_page() so nothing is anonymous.

  Paul

> Jan


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