Re: [Xen-devel] [PATCH linux-2.6.18] xen: mark pvscsi frontend request consumed only after last read

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 30.01.15 at 14:51, <"jgross@xxxxxxxx".non-mime.internet> wrote:
> A request in the ring buffer mustn't be read after it has been marked
> as consumed. Otherwise it might already have been reused by the
> frontend without violating the ring protocol.

This is irrelevant, as the ->req_cons is a backend private field (if it
was a shared one, a barrier would have been needed between
copying and updating that field).

> To avoid inconsistencies in the backend only work on a private copy
> of the request. This will ensure a malicious guest not being able to
> bypass consistency checks of the backend by modifying an active
> request.

Hence - also considering with my earlier reply - I don't view the change
as necessary.

Jan


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