Re: [Xen-devel] Multiple-page mem_event ring buffer?

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Tue, Mar 05, 2013 at 03:21:38PM +0200, Razvan Cojocaru wrote:
> Hello,
> 
> currently my code (and all the examples I could find in the Xen
> source code) uses a single page mem_event ring buffer, using code
> along the lines of:
> 
> /* Map the ring page */
> unsigned long ring_pfn;
> xc_get_hvm_param(xci_, domain_, HVM_PARAM_ACCESS_RING_PFN, &ring_pfn);
> 
> unsigned long mmap_pfn = ring_pfn;
> ringPage_ = xc_map_foreign_batch(xci_, domain_, PROT_READ | PROT_WRITE,
>                                  &mmap_pfn, 1);
> 
> if (mmap_pfn & XEN_DOMCTL_PFINFO_XTAB) {
> 
>     /* Map failed, populate ring page */
>     if (xc_domain_populate_physmap_exact(xci_, domain_,
>                                          1, 0, 0, &ring_pfn))
>         return SOME_ERROR;
> 
>     mmap_pfn = ring_pfn;
>     ringPage = xc_map_foreign_batch(xci_, domain_,
>                                     PROT_READ | PROT_WRITE,
>                                     &mmap_pfn, 1);
> 
>     if (mmap_pfn & XEN_DOMCTL_PFINFO_XTAB)
>         return SOME_OTHER ERROR;
> }
> 
> Could I safely use more than one page for the ring buffer (passing
> '2' as the last parameter of xc_map_foreign_batch(), and so on), or
> am I limited to 1 page by design?

You should be able to as many as you want. Are you hitting any
particular issues?

> 
> 
> Thanks,
> Razvan Cojocaru
> 
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> http://lists.xen.org/xen-devel
> 

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