Re: [Qemu-devel] [PATCH v4 2/2] spapr-pci: Enable huge BARs

[David Gibson]

On Fri, Jan 30, 2015 at 12:53:19PM +1100, Alexey Kardashevskiy wrote:
> At the moment sPAPR only supports 512MB window for MMIO BARs. However
> modern devices might want bigger 64bit BARs.
> 
> This extends MMIO window from 512MB to 62GB (aligned to
> SPAPR_PCI_WINDOW_SPACING) and advertises it in 2 records in
> the PHB "ranges" property. 32bit gets the space from
> SPAPR_PCI_MEM_WIN_BUS_OFFSET till the end of 4GB, 64bit gets the rest
> of the space. If no space is left, 64bit range is not advertised.
> 
> The MMIO space size is set to old value of 0x20000000 by default
> for pseries machines older than 2.3.
> 
> The approach changes the device tree which is a guest visible change, however
> it won't break migration as:
> 1. we do not support migration to older QEMU versions
> 2. migration to newer QEMU will migrate the device tree as well and since
> the new layout only extends the old one and does not change address mappigns,
> no breakage is expected here too.
> 
> SLOF change is required to utilize this extension.
> 
> Suggested-by: Benjamin Herrenschmidt <address@hidden>
> Signed-off-by: Alexey Kardashevskiy <address@hidden>

Reviewed-by: David Gibson <address@hidden>

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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