Re: [Xen-devel] [PATCH 1/2] arm: implement hypercall continuations

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 23 Jul 2012, Ian Campbell wrote:
> Largely cribbed from x86, register names differ and the return value is r0 ==
> the first argument rather than the hypercall number (which is r12).
> 
> Multicall variant is untested, arms do_multicall_call is currently a BUG() so
> we obviously don't use that yet. I have left a BUG in the hypercall
> continuation path too since it will need validation once multicalls are
> implemented.
> 
> Since the multicall state is local we do not need a globally atomic
> {test,set}_bit. However we do need to be atomic WRT interrupts so can't just
> use the naive RMW version. Stick with the global atomic implementation for now
> but keep the __ as documentaion of the intention.
> 
> We cannot clobber all argument registers in a debug build anymore
> because continuations expect them to be preserved. Add nr_args field to the
> hypercall dispatch array and use it to only clobber the unused hypercall
> arguments.
> 
> While debugging this I noticed that hypercall dispatch will happily run off 
> the
> end of the hypercall dispatch array, add a suitable bounds check.
> 
> Signed-off-by: Ian Campbell <Ian.Campbell@xxxxxxxxxx>

Acked-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>


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