Re: [PATCH v2] xen: Add RING_COPY_RESPONSE()

[Jürgen Groß <jgross@xxxxxxxx>]

On 28.01.21 16:50, Marek Marczykowski-Górecki wrote:
> Using RING_GET_RESPONSE() on a shared ring is easy to use incorrectly
> (i.e., by not considering that the other end may alter the data in the
> shared ring while it is being inspected). Safe usage of a response
> generally requires taking a local copy.
>
> Provide a RING_COPY_RESPONSE() macro to use instead of
> RING_GET_RESPONSE() and an open-coded memcpy().  This takes care of
> ensuring that the copy is done correctly regardless of any possible
> compiler optimizations.
>
> Use a volatile source to prevent the compiler from reordering or
> omitting the copy.
>
> This generalizes similar RING_COPY_REQUEST() macro added in 3f20b8def0.
>
> Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>


Juergen

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