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Re: [Qemu-devel] [PATCH qemu v10 05/14] spapr_iommu: Introduce "enabled"

From: David Gibson
Subject: Re: [Qemu-devel] [PATCH qemu v10 05/14] spapr_iommu: Introduce "enabled" state for TCE table
Date: Mon, 6 Jul 2015 20:07:32 +1000
User-agent: Mutt/1.5.23 (2014-03-12)

On Mon, Jul 06, 2015 at 12:11:01PM +1000, Alexey Kardashevskiy wrote:
> Currently TCE tables are created once at start and their size never
> changes. We are going to change that by introducing a Dynamic DMA windows
> support where DMA configuration may change during the guest execution.
> This changes spapr_tce_new_table() to create an empty stub object. Only
> LIOBN is assigned by the time of creation. It still will be called once
> at the owner object (VIO or PHB) creation.
> This introduces an "enabled" state for TCE table objects with two
> helper functions - spapr_tce_table_enable()/spapr_tce_table_disable().
> spapr_tce_table_enable() receives TCE table parameters and allocates
> a guest view of the TCE table (in the user space or KVM).
> spapr_tce_table_disable() disposes the table.
> Follow up patches will disable+enable tables on reset (system reset
> or DDW reset).
> No visible change in behaviour is expected except the actual table
> will be reallocated every reset. We might optimize this later.
> The other way to implement this would be dynamically create/remove
> the TCE table QOM objects but this would make migration impossible
> as migration expects all QOM objects to exist at the receiver
> so we have to have TCE table objects created when migration begins.
> spapr_tce_table_do_enable() is separated from from spapr_tce_table_enable()
> as later it will be called at the sPAPRTCETable post-migration stage when
> it has all the properties set after the migration.
> 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_!

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