Hi Gustavo,
I understood difference between the two patchsets. thanks for the
ivshmem-flat. i will try to get info from QNX side how to access the memory
location in QNX. with the ivshmem-flat enabled, i am able to see shmem in
"info qtree" as below
(qemu) info qtree
bus: main-system-bus
type System
dev: ivshmem-flat, id ""
gpio-out "sysbus-irq" 1
chardev = "ivshmem_flat"
shmem-size = 4194304 (0x400000)
x-irq-qompath = "/machine/unattached/device[4]/gic/unnamed-gpio-in[0]"
x-bus-address-iomem = 1074786304 (0x400ff000)
x-bus-address-shmem = 1074790400 (0x40100000)
mmio 00000000400ff000/0000000000000010
mmio 0000000040100000/0000000000400000
now need to explore in guest os(QNX) on how to read this memory location.
On Thu, May 16, 2024 at 11:35 PM Sanjeev Kumar <reachsanje...@gmail.com>
wrote:
> Hi Gustavo,
> Thanks for your reply. Will try it out.
> But i see two set of patches.
>
> https://lore.kernel.org/qemu-devel/20240222222218.2261956-1-gustavo.rom...@linaro.org/
>
> And
>
>
> https://lore.kernel.org/qemu-devel/20231127052024.435743-2-gustavo.rom...@linaro.org/
>
> First one looks latest. But when i use them, it is throwing error of
> property is missing
>
> x-bus-qompath
>
> Please check and let me know which is correct patchset to use.
>
> Thanks & Regards
>
> On Thu, 16 May 2024 at 3:59 PM, Gustavo Romero <gustavo.rom...@linaro.org>
> wrote:
>
>> Hi Sanjeev,
>>
>> On 5/16/24 11:22 AM, Sanjeev Kumar wrote:
>> > Hi Philippe,
>> > I have taken patches from the link you provided
>> > and built QEMU and started appending below line to QEMU
>> >
>> > -chardev socket,path=/tmp/ivshmem_socket,id=ivshmem_flat -device
>> ivshmem-flat,chardev=ivshmem_flat,x-irq-qompath='/machine/unattached/device[4]/gic/unnamed-gpio-in[0]',x-bus-qompath='/sysbus'
>> >
>> > and QEMU boots without any error
>> >
>> > I would like to get some help regarding data writing and reading from
>> shared memory.
>> >
>> > when using ivshmem-plain, i used to write data from host like
>> > echo "hello" > /dev/shm/shm1 and in guest i was reading from pci bus
>> BAR and i was able to get data.
>> >
>> > similarly can you please help me with ivshmem-flat like where is the
>> location to write/read the data from host and in guest.
>>
>> Writing/reading from the host must work the same way as in ivshmem PCI.
>> It's
>> ultimately the ivshmem-server's duty to create, map, and distribute the
>> file
>> descriptors to the VMs (guests), so nothing changes. I haven't tried it
>> tho,
>> I testes it directly writing it from the other guest running Linux with
>> ivshmem
>> PCI attached. But, it should work the same, yep.
>>
>> I don't know anything about QNX, but if you have access to real
>> addresses, this
>> would work the same as in Zephyr (where I tested it). You just need to
>> pass to
>> the ivshmem-flat driver the address where you want to map the shm and the
>> MMRs
>> using the x-bus-address-shmem and the x-bus-address-iomem, respectively,
>> like,
>> for instance:
>>
>> x-bus-address-iomem=0x400FF000,x-bus-address-shmem=0x40100000
>>
>> then you can read/write directly from/to the address specified in by
>> x-bus-address-shmem that data will appear in the other peers (guests)
>> and also should be able to get accessed from the host as well.
>>
>> For instance, in Zephyr I used the following test to exercise ivshmem-flat
>> from the Cortex-M guest, which has the addresses hardcoded and uses them
>> directly:
>>
>>
>> https://github.com/gromero/zephyr/commit/73fbd481e352b25ae5483ba5048a2182b90b7f00#diff-16fa1f481a49b995d0d1a62da37b9f33033f5ee477035e73465e7208521ddbe0R9-R96
>>
>>
>> HTH,
>> Gustavo
>>
>
