Re: [Xen-devel] [PATCH v3 4/5] tools, libxl: parse optional start gfn from the iomem config option

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hello Arianna,

Few other comments on this patch :)

On 03/15/2014 08:11 PM, Arianna Avanzini wrote:
> diff --git a/docs/man/xl.cfg.pod.5 b/docs/man/xl.cfg.pod.5
> index a6663b9..d9684f2 100644
> --- a/docs/man/xl.cfg.pod.5
> +++ b/docs/man/xl.cfg.pod.5
> @@ -602,12 +602,13 @@ is given in hexadecimal and may either a span e.g. 
> C<2f8-2ff>
>  It is recommended to use this option only for trusted VMs under
>  administrator control.
>  
> -=item B<iomem=[ "IOMEM_START,NUM_PAGES", "IOMEM_START,NUM_PAGES", ... ]>
> +=item B<iomem=[ "IOMEM_START,NUM_PAGES[@GFN]", 
> "IOMEM_START,NUM_PAGES[@GFN]", ... ]>
>  
>  Allow guest to access specific hardware I/O memory pages. B<IOMEM_START>
>  is a physical page number. B<NUM_PAGES> is the number
> -of pages beginning with B<START_PAGE> to allow access. Both values
> -must be given in hexadecimal.
> +of pages beginning with B<START_PAGE> to allow access. B<GFN> specifies
> +the guest frame number where the mapping will start in the domU's
> +address space. All of these values must be given in hexadecimal.

I'm wondering if we should add something about IOMMU. On ARM (I don't
know for x86), the IOMMU won't be updated. That would mean every device
protected by an IOMMU *should not* be passthrough via "iomem" parameter.

Regards,

-- 
Julien Grall

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