Re: CXL emulation on aarch64

[Jonathan Cameron]

On Thu, 16 Jan 2025 15:04:53 +0900
Itaru Kitayama <itaru.kitayama@linux.dev> wrote:

> Hi Jonathan,
> 
> > On Jan 14, 2025, at 19:26, Jonathan Cameron <Jonathan.Cameron@huawei.com> 
> > wrote:
> > 
> > On Tue, 14 Jan 2025 12:03:03 +0900
> > Itaru Kitayama <itaru.kitayama@linux.dev> wrote:
> >   
> >> Hi Jonathan, 
> >>   
> >>> On Jan 10, 2025, at 21:31, Jonathan Cameron <Jonathan.Cameron@huawei.com> 
> >>> wrote:
> >>> 
> >>> On Fri, 10 Jan 2025 09:20:54 +0000
> >>> "Zhijian Li (Fujitsu)" via <qemu-devel@nongnu.org> wrote:
> >>>   
> >>>> On 10/01/2025 13:29, Itaru Kitayama wrote:    
> >>>>> Hi,
> >>>>> Is anybody working on the CXL emulation on aarch64?      
> >>>> 
> >>>> I'm not currently working on the CXL emulation on aarch64.
> >>>> 
> >>>> However, IIRC the CXL maintainer's tree should work.
> >>>> https://gitlab.com/jic23/qemu/    
> >>> 
> >>> Pick up latest branch from there. I'm prepping a rebased version
> >>> with some new stuff but might take a few more days.    
> >> 
> >> Thanks for sharing your work with us.  Your master and cxl-2024-11-27 
> >> branches give:
> >> 
> >> $ qemu-system-aarch64: -accel tcg,cxl=on: Property 'tcg-accel.cxl' not 
> >> found  
> > 
> > cxl is a machine property not a accel one. So needs to be after virt
> > There are tests in the tree for bios tables. Copy the command line from 
> > those.
> >   
> >> 
> >> My commands are below:
> >> $HOME/projects/qemu/build/qemu-system-aarch64 \
> >>        -M virt,virtualization=on,gic-version=3 \
> >>        -M acpi=off -cpu max,sme=off -m 8G -smp 4 \
> >>        -accel tcg,cxl=on \
> >>        -nographic \
> >>        -bios $HOME/cca-v4/out/bin/flash.bin \
> >>        -kernel Image-cca \
> >>        -drive 
> >> format=raw,if=none,file=$HOME/cca-v4/out-or/images/rootfs.ext2,id=hd0 \
> >>        -device virtio-blk-pci,drive=hd0 \
> >>        -append root=/dev/vda \
> >>        -nodefaults \
> >>        --serial tcp:localhost:54320 \
> >>         -serial tcp:localhost:54321 \
> >>         -append "root=/dev/vda earlycon console=hvc0" \
> >>         -device virtio-net-pci,netdev=net0 \
> >>         -netdev user,id=net0 \
> >>         -device virtio-9p-device,fsdev=shr0,mount_tag=shr0 \
> >>         -fsdev local,security_model=none,path=../../,id=shr0
> >> 
> >> Yes, I’m using Linaro’s CCA capable OP-TEE builds above.  
> > 
> > I'm a little curious why optee is relevant for this but shouldn't matter as 
> > long
> > as an appropriate EDK2 is loaded.
> >   
> 
> I picked up your tree’s “master” and “cxl-next” as of today, and only the 
> latter at least booted.
> The former gives:
> 
> qemu-system-aarch64: Property 'virt-9.2-machine.cxl' not found
> 
> Should I stick with the cxl-next? My concern is that the base QEMU version is 
> a bit old
> 7.0.50.

Always use the latest dated branch on that tree.  I release whenever there
is something new to carry or a major rebase needed.

cxl-<date> is the right branch to use. Hope that helps.

Jonathan

> 
> Thanks,
> Itaru.
> 
> > Jonathan
> >   
> >> 
> >> Let me know which branch you were suggesting.
> >> 
> >> Thanks,
> >> Itaru. 
> >>   
> >>> 
> >>> Note my main development work is on arm64 so that tends to work
> >>> more reliably than x86 which I only lightly test for stuff that
> >>> isn't ready for upstream yet.
> >>> 
> >>> Give me a shout if you run into any problems.
> >>> 
> >>> The main blocker on upstreaming this is resolving the missing device tree
> >>> support for PCI expander bridges.  I've not made any progress on this 
> >>> since
> >>> talk at Linaro connect in 2023.
> >>> 
> >>> Jonathan
> >>> 
> >>>   
> >>>> 
> >>>> 
> >>>> Thanks
> >>>> Zhijian
> >>>>   
> >>>>> If there’s a WIP branch, a pointer would be appreciated.
> >>>>> 
> >>>>> Itaru      
> 
>