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From: Pavel Fedin <p.fedin@samsung.com>
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Date: Fri, 04 Sep 2015 10:26:14 +0300
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Subject: Re: [Qemu-devel] [PATCH v12 5/5] hw/arm/virt: Add
 gic-version	option to virt machine
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To: 'Peter Maydell' <peter.maydell@linaro.org>
Cc: 'Shlomo Pongratz' <shlomo.pongratz@huawei.com>, 'Shlomo Pongratz' <shlomopongratz@gmail.com>, 'QEMU Developers' <qemu-devel@nongnu.org>, 'Eric Auger' <eric.auger@linaro.org>

 Hello!

> Why have separate ITS_CONTROL and ITS_TRANSLATION entries, given
> that the ITS pages are architecturally required to be contiguous
> and the dt binding doesn't require you to specify the two addresses
> separately?

 It is more convenient for ITS implementation. I already have the code =
for it, and for ITS device it is useful to have two separate sysbus-mmio =
regions, one for control and one for translation. Because control area =
is fed to KVM and translation area is handled by qemu in userspace, =
because it has to catch writes and inject them as KVM_SIGNAL_MSI =
ioctl's. So, i have to map two regions, therefore i need two bases. =
Sizes are just added together when i create DT binding.
 Well, i could do the opposite, store them as a single region in memory =
map, and just add the appropriate offset when mapping the second =
sysbus-mmio region. It's the same amount of arithmetic, actually. What =
would you prefer?

Kind regards,
Pavel Fedin
Expert Engineer
Samsung Electronics Research center Russia