RE: Xen and Qemu virtio question

[Peng Fan <peng.fan@xxxxxxx>]

Hi Vikram,

> Subject: Re: Xen and Qemu virtio question
> 
> Hi Peng,
> Please see my comments below.
> On Wed, Jan 03, 2024 at 05:38:07AM +0000, Peng Fan wrote:
> > Hi Vikram, Oleksii
> >
> > I follow the slide virtio for Xen on ARM[1], but I met some issues,
> > and stuck for about two days.
> >
> > I use upstream lastest qemu repo master branch, not qemu-xen.git repo.
> This is right.
> >
> > My start command as below[2], but seems I need first `xl create
> > domu.cfg`, otherwise it will fail, because xen hypervisor
> > dm_op->rcu_lock_remote_domain_by_id will return failure if domu not
> > created.  My domu cfg is simple:
> > kernel = "/run/media/boot-mmcblk1p1/Image"
> > disk = [ '/etc/xen/disk_1.img,,xvda,specification=virtio' ] cmdline =
> > "console=hvc0 root=/dev/xvda rw"
> > name = "DomU"
> > memory = 512
> > serial = "pty"
> >
> > I drop qdisk in the disk entry, because xen tool report qdisk and
> > virtio not compatible.
> >
> > And the arg xen_domid should be same as domu domain id? Is there any
> > dynamic way to set xen_domid, start qemu when start domu?
> Yes, it should be xen_domid. Below virtio-disk patches will take care of
> invoking QEMU with right domid.
> >
> > Does the domu dts still needed to include the virtio,mmio node?
> >
> > however xl create domu.cfg relies virtio disk ready, which needs qemu
> > start first. This confuses me. How do you address this or I do
> > something wrong?
> >
> > Then after xl create,  I quickly start qemu, but met:
> > failed to create ioreq server, then I see there is mismatch.
> > qemu use HVM_IOREQSRV_BUFIOREQ_ATOMIC to create ioreq server, but
> xen
> > ioreq_server_create will return failure:
> >      if ( !IS_ENABLED(CONFIG_X86) && bufioreq_handling )
> >                return -EINVAL;
> >
> There is a downstream patch for this:
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub
> .com%2FXilinx%2Fxen%2Fcommit%2Fbe35b46e907c7c78fd23888d837475e
> b28334638&data=05%7C02%7Cpeng.fan%40nxp.com%7C52a0d96c7d95474
> c016408dc0c9cbc2e%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%
> 7C638399114509848564%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLj
> AwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%
> 7C%7C&sdata=KylGkFrL2hOazsLjFwwj%2FIAPDQU80LhFfONQL4ytaic%3D&re
> served=0
> 
> > So I change HVM_IOREQSRV_BUFIOREQ_OFF in qemu, but met:
> > qemu-system-aarch64: failed to map ioreq server resources: error 2
> > handle=0xaaaad26c7f30
> > qemu-system-aarch64: xen hardware virtual machine initialisation
> > failed
> >
> > Do you have out of box repo that works well? Including Qemu and Xen, I
> > am trying virtio disk, but will move to test virtio gpu soon.
> >
> > I am not sure there are some downstream patches in your side to
> > address and make it work well.
> >
> We have a few downstream patches for xen-tools.
> For Virtio disk backend:
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub
> .com%2FXilinx%2Fxen%2Fcommit%2F947280803294bbb963f428423f679d0
> 74c60d632&data=05%7C02%7Cpeng.fan%40nxp.com%7C52a0d96c7d95474
> c016408dc0c9cbc2e%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%
> 7C638399114509848564%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLj
> AwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%
> 7C%7C&sdata=%2Bfjlzz%2Bvut3WyRWARfCij03kJ5ZuiGIika8uK5MIdM8%3D&
> reserved=0
> For Virtio-net:
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub
> .com%2FXilinx%2Fxen%2Fcommit%2F32fcc702718591270e5c8928b7687d8
> 53249c882&data=05%7C02%7Cpeng.fan%40nxp.com%7C52a0d96c7d95474
> c016408dc0c9cbc2e%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%
> 7C638399114509848564%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLj
> AwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%
> 7C%7C&sdata=BLtX2GbY77J65H6mBF1r3nXkCWN%2B0SfRJTkH1CnTiQE%3D
> &reserved=0
> For changing the machine name to Xenpvh(to align with QEMU changes):
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub
> .com%2FXilinx%2Fxen%2Fcommit%2F5f669949c9ffdb1947cb47038956b5fb
> 8eeb072a&data=05%7C02%7Cpeng.fan%40nxp.com%7C52a0d96c7d95474c
> 016408dc0c9cbc2e%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7
> C638399114509848564%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjA
> wMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7
> C%7C&sdata=FbmQpeyrc86qapDK8gDNr7o0fYj09t6RrBA3RdmR4EQ%3D&res
> erved=0
> 
> With above 4 patches it should work for you. Please re-compile Xen and Xen-
> tools first and finally compile QEMU with this Xen.

Thanks very much on your information. I will pick up your patches and
give a try.

BTW, any plan to upstream the patches?

Thanks,
Peng.

> 
> > Thanks for your help.
> >
> > Thanks,
> > Peng.
> >
> > [1]https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fw
> >
> ww.youtube.com%2Fwatch%3Fv%3DboRQ8UHc760&data=05%7C02%7Cpen
> g.fan%40nxp
> > .com%7C52a0d96c7d95474c016408dc0c9cbc2e%7C686ea1d3bc2b4c6fa9
> 2cd99c5c30
> >
> 1635%7C0%7C0%7C638399114509848564%7CUnknown%7CTWFpbGZsb3d
> 8eyJWIjoiMC4w
> >
> LjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C
> %7C%7C
> >
> &sdata=VUs6u5qmXi7X5M0JgYJypNO10SIdFkBdVz7RRmUkuNM%3D&reserv
> ed=0
> >
> > [2]qemu-system-aarch64  -xen-domid 1 \ -chardev
> > socket,id=libxl-cmd,path=qmp-libxl-1,server=on,wait=off \ -mon
> > chardev=libxl-cmd,mode=control \ -chardev
> > socket,id=libxenstat-cmd,path=qmp-libxenstat-1,server=on,wait=off \
> > -mon chardev=libxenstat-cmd,mode=control \ -xen-attach -name guest0
> > -vnc none -display none -nographic \ -machine xenpvh -m 513 &