Re: [Xen-devel] [RFC 15/19] xen/arm: Reserve region in guest memory for device passthrough

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 16 Jun 2014, Julien Grall wrote:
> This region will be split by the toolstack to allocate MMIO range for eac
> device.
> 
> For now only reserve a 512MB region, this should be enought to passthrough
> multiple device at the same time.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> ---
>  xen/include/public/arch-arm.h |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/xen/include/public/arch-arm.h b/xen/include/public/arch-arm.h
> index ac54cd6..789bffb 100644
> --- a/xen/include/public/arch-arm.h
> +++ b/xen/include/public/arch-arm.h
> @@ -369,6 +369,10 @@ typedef uint64_t xen_callback_t;
>  #define GUEST_GICC_BASE   0x03002000ULL
>  #define GUEST_GICC_SIZE   0x00000100ULL
>  
> +/* Space for mapping MMIO from device passthrough: 512MB @ 256MB*/
> +#define GUEST_MMIO_BASE   0x10000000ULL
> +#define GUEST_MMIO_SIZE   0x20000000ULL

Is it really necessary to specify size here? It looks like an artifical
limitation to me: given that is unlikely that we'll ever be able to
support non-PCI device hotplug, we only have to handle cold-plug here.
So the toolstack has all the information it needs to build the perfect
memory layout for the guest at VM creation time.


>  /* 16MB == 4096 pages reserved for guest to use as a region to map its
>   * grant table in.
>   */
> -- 
> 1.7.10.4
> 
> 
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> 

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