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Re: [Qemu-devel] [PATCH 17/21] introduce memory_region_get_address() and


From: Peter Maydell
Subject: Re: [Qemu-devel] [PATCH 17/21] introduce memory_region_get_address() and use it in kvm/ioapic
Date: Tue, 23 Apr 2013 19:00:14 +0100

On 23 April 2013 18:39, Jan Kiszka <address@hidden> wrote:
> On 2013-04-23 19:26, Peter Maydell wrote:
>> That would be an improvement, but it still requires this
>> device to know what address space it's mapped into, which
>> is a bit ugly.
>
> Unfortunately the KVM API mandates this knowledge (IOAPIC state contains
> the absolute mapping address). So we need some channel to explore where
> this device is mapped.

For ARM we defer the mechanics of "tell the kernel where this memory
region is" from the device implementation (hw/intc/arm_gic_kvm.c) to
generic code in target-arm/kvm.c, which I personally think is a
neat way to solve this problem. It looks like the x86 ABI has
tied up one-time config stuff (like the base address) with
generic state save/load though, so that doesn't quite work for
the x86 case.

Anyway, I think I've previously argued on this list against having
a "return address of this MR in this AddressSpace" function in the
API, but I've changed my mind on that: it's kind of equivalent to
the listener API functionality except it's a one-off query.

NB: I don't think we should call it memory_region_get_address()
though -- that implies a non-existent parallel to the current
memory_region_set_address().

thanks
-- PMM



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