Re: [Xen-devel] [PATCH 15/25] argo: implement the sendv op

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Fri, Jan 04, 2019 at 12:13:09AM -0800, Christopher Clark wrote:
> 2) the p2m type of the guest-supplied memory for the ring.
> 
> Roger raised a query about not pinning the p2m type of memory
> used for the ring, and my response on 21st December is here:
> 
> https://lists.xenproject.org/archives/html/xen-devel/2018-12/msg02204.html
> 
> At the moment, I haven't changed that code. If the p2m type is changed
> after ring registration, is it a problem? If not, then I think the code is
> OK; but if so then a pointer to what makes it problematic would be
> helpful to determine an appropriate next step.

My point was that you don't need to check every time that the gfn ->
mfn translations for the ring are the same (as is done in
argo_find_ring_mfns). AFAICT you take a reference to each page in the
ring, so there's no need to check that the p2m mapping is still the
same.

I think the p2m type checks that you do are correct, and you should
only allow p2m_ram_rw pages to be used for the ring.

Roger.

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