Il 03/06/2013 12:25, Peter Maydell ha scritto: > On 3 June 2013 11:12, Paolo Bonzini <pbonz...@redhat.com> wrote: >> 1) I could set the owner to NULL before calling the sysbus_init_mmio; >> >> 2) I could add a variant of sysbus_init_mmio that doesn't set the owner; >> >> 3) I could skip setting the owner for sysbus altogether, since it is >> only strictly required for unpluggable devices. > > 4) you could set the owner at the right place, ie when the > memory region is created. > >> However, I think there is worth in preserving the chain through either >> containment or aliasing. From the nesting point of view, >> realview_mpcore is exposing the region. From the implementor point of >> view, arm_gic is implementing the region (and arm_gic is the one that >> would be ref/unref'd at execution time). In either case, >> arm11mpcore_priv is not what you want to see. Its presence is just an >> implementation detail of realview_mpcore. > > I agree that the owner of the MR in this case should be > arm_gic.
The owner of the I/O region is arm_gic. It is set when arm_gic does sysbus_init_mmio. But container regions have an owner too. Here the owner is set initially to arm11mpcore_priv, and then it bombs when realview_mpcore tries to change it to itself. Make each level wrap the region with a container makes sense to me. But actually sysbus_pass_mmio would match nicely sysbus_pass_irq as an API, so (2) above would be a good choice too. What I'm definitely not going to do, is go through 800 calls and add owners to all of them. > For aliasing, surely you need to actually reference > both devices? If the device that owns the container goes > away then your MR* is toast anyway, and if the device doing > the actual implementation goes away your MR* is also now > invalid. So they have to both hang around long enough for > you to finish whatever you were doing. Container and alias regions are "virtual", they are eliminated while creating the flat memory map; I/O goes straight to the contained/aliased region. Hence, containers and aliases in principle need no owner; it is still nice to have one, for symmetry and ease of debugging. A reference to the aliased region is added when: (1) the region is added to the flat memory map; (2) the alias is created. Both are done in patch 3. Paolo
