Re: [PATCH v4] virtio-mmio: improve virtio-mmio get_dev_path alog

[Peter Maydell <peter.maydell@linaro.org>]

On Thu, 25 Feb 2021 at 05:36, schspa <schspa@gmail.com> wrote:
>
> At the moment the following QEMU command line triggers an assertion
> failure On xlnx-versal SOC:
>   qemu-system-aarch64 \
>       -machine xlnx-versal-virt -nographic -smp 2 -m 128 \
>       -fsdev local,id=shareid,path=${HOME}/work,security_model=none \
>       -device virtio-9p-device,fsdev=shareid,mount_tag=share \
>       -fsdev local,id=shareid1,path=${HOME}/Music,security_model=none \
>       -device virtio-9p-device,fsdev=shareid1,mount_tag=share1
>
>   qemu-system-aarch64: ../migration/savevm.c:860:
>   vmstate_register_with_alias_id:
>   Assertion `!se->compat || se->instance_id == 0' failed.
>
> This problem was fixed on arm virt platform in commit f58b39d2d5b
> ("virtio-mmio: format transport base address in BusClass.get_dev_path")
>
> It works perfectly on arm virt platform. but there is still there on
> xlnx-versal SOC.
>
> The main difference between arm virt and xlnx-versal is they use
> different way to create virtio-mmio qdev. on arm virt, it calls
> sysbus_create_simple("virtio-mmio", base, pic[irq]); which will call
> sysbus_mmio_map internally and assign base address to subsys device
> mmio correctly. but xlnx-versal's implements won't do this.
>
> However, xlnx-versal can't switch to sysbus_create_simple() to create
> virtio-mmio device. It's because xlnx-versal's cpu use
> VersalVirt.soc.fpd.apu.mr as it's memory. which is subregion of
> system_memory. sysbus_create_simple will add virtio to system_memory,
> which can't be accessed by cpu.
>
> Besides, xlnx-versal can't add sysbus_mmio_map api call too, because
> this will add memory region to system_memory, and it can't be added
> to VersalVirt.soc.fpd.apu.mr again.
>
> We can solve this by assign correct base address offset on dev_path.
>
> This path was test on aarch64 virt & xlnx-versal platform.
>
> Signed-off-by: schspa <schspa@gmail.com>
> ---

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

Applied to target-arm.next, thanks (unless MST would rather it
go in via another route).

-- PMM