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Re: [PATCH] arm: xlnx-versal: fix virtio-mmio base address assignment

From: Philippe Mathieu-Daudé
Subject: Re: [PATCH] arm: xlnx-versal: fix virtio-mmio base address assignment
Date: Fri, 5 Feb 2021 11:31:35 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0

On 2/5/21 11:03 AM, Peter Maydell wrote:
> On Fri, 5 Feb 2021 at 07:53, Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
>> Indeed, you found a design issue IMO:
>> Versal creates the "mr-ps-switch" to be explicitly different from
>> the main sysbus memory. TYPE_VIRTIO_MMIO is a SYSBUS device, thus
>> can not be created without being plugged on sysbus.
>> We want TYPE_VIRTIO_MMIO to be TYPE_USER_CREATABLE so we can create
>> it on the command line (like your usage). TYPE_SYSBUS allows such
>> automatic plug it on the main bus, but also maps to main memory.
> That was never the design intent for the virtio mmio transport.
> The idea was that the board creates a bunch of transports
> (unconditionally). The user then uses command line options
> to create virtio backends (blk, net, etc) which get plugged
> into the virtio-bus buses that each transport has.
> virtio-mmio is not user-creatable for the same reason that
> all devices with MMIO memory regions and IRQ lines are not
> user-creatable -- there's no good command line syntax for
> the user to wire them up, and we don't want the user to have
> to know "on this board address 0x50003000 is a good place to
> put a device, and irq 43 is free".

1/ virtio-mmio must be sysbus-device,
2/ we can not sysbus-map out of main memory so private container
is incorrect, and Versal can not use "mr-ps-switch"?

> thanks
> -- PMM

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