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Date: Thu, 04 Jun 2015 10:05:08 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v2 15/23] target-i386: use memory API to
 implement SMRAM
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To: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>, Laszlo Ersek <lersek@redhat.com>, "qemu-devel@nongnu.org Developers" <qemu-devel@nongnu.org>, Gerd Hoffmann <kraxel@redhat.com>



On 04/06/2015 09:19, Peter Crosthwaite wrote:
> > Remove cpu_smm_register and cpu_smm_update.  Instead, each CPU
> > address space gets an extra region which is an alias of
> > /machine/smram.  This extra region is enabled or disabled
> > as the CPU enters/exits SMM.
>
> Why is the connectivity from machine->CPU made via a predetermined
> canon path? This has come up for me a few times out-of-tree and I have
> managed it via links. Can the machine create the smram bus as a
> MemoryRegion and in a loop pass it to each CPU via a MemoryRegion *
> link?

I did it this way because there's only one SMRAM---it's basically a part
of address_space_memory that's usually hidden, and there's only one
address_space_memory.

Also, KVM would not support separate per-CPU SMRAMs, even if they
existed on real hardware, so a single per-machine object made more sense
to me.

Paolo