Re: [Xen-devel] [PATCH] x86/HVM: correct last address emulation acceptance check

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 26 April 2016 09:23
> To: xen-devel
> Cc: Paul Durrant; Wei Liu
> Subject: [PATCH] x86/HVM: correct last address emulation acceptance check
> 
> For REPeated memory access instructions the repeat count also needs to
> be considered. Utilize that "last" already takes this into account.
> 
> Also defer computing "last" until we really know we need it.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Paul Durrant <paul.durrant@xxxxxxxxxx>

> 
> --- a/xen/arch/x86/hvm/intercept.c
> +++ b/xen/arch/x86/hvm/intercept.c
> @@ -34,16 +34,16 @@
>  static bool_t hvm_mmio_accept(const struct hvm_io_handler *handler,
>                                const ioreq_t *p)
>  {
> -    paddr_t first = hvm_mmio_first_byte(p);
> -    paddr_t last = hvm_mmio_last_byte(p);
> +    paddr_t first = hvm_mmio_first_byte(p), last;
> 
>      BUG_ON(handler->type != IOREQ_TYPE_COPY);
> 
>      if ( !handler->mmio.ops->check(current, first) )
>          return 0;
> 
> -    /* Make sure the handler will accept the whole access */
> -    if ( p->size > 1 &&
> +    /* Make sure the handler will accept the whole access. */
> +    last = hvm_mmio_last_byte(p);
> +    if ( last != first &&
>           !handler->mmio.ops->check(current, last) )
>          domain_crash(current->domain);
> 
> 
> 


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