Re: CXL volatile memory is not listed

[Maverickk 78]

Jonathan,

> More generally for the flow that would bring the memory up as system ram
> you would typically need the bios to have done the CXL enumeration or
> a bunch of scripts in the kernel to have done it.  In general it can't
> be fully automated, because there are policy decisions to make on things like
> interleaving.

BIOS CXL enumeration? is CEDT not enough? or BIOS further needs to
create an entry
in the e820 table?

>
> I'm not aware of any open source BIOSs that do it yet.  So you have
> to rely on the same kernel paths as for persistent memory - manual 
> configuration
> etc in the kernel.
>
Manual works with "cxl create regiton"  :)

On Thu, 10 Aug 2023 at 16:05, Jonathan Cameron
<Jonathan.Cameron@huawei.com> wrote:
>
> On Wed, 9 Aug 2023 04:21:47 +0530
> Maverickk 78 <maverickk1778@gmail.com> wrote:
>
> > Hello,
> >
> > I am running qemu-system-x86_64
> >
> > qemu-system-x86_64 --version
> > QEMU emulator version 8.0.92 (v8.1.0-rc2-80-g0450cf0897)
> >
> +Cc linux-cxl as the answer is more todo with linux than qemu.
>
> > qemu-system-x86_64 \
> > -m 2G,slots=4,maxmem=4G \
> > -smp 4 \
> > -machine type=q35,accel=kvm,cxl=on \
> > -enable-kvm \
> > -nographic \
> > -device pxb-cxl,id=cxl.0,bus=pcie.0,bus_nr=52 \
> > -device cxl-rp,id=rp0,bus=cxl.0,chassis=0,port=0,slot=0 \
> > -object memory-backend-file,id=mem0,mem-path=/tmp/mem0,size=1G,share=true \
> > -device cxl-type3,bus=rp0,volatile-memdev=mem0,id=cxl-mem0 \
> > -M cxl-fmw.0.targets.0=cxl.0,cxl-fmw.0.size=1G
>
> There are some problems upstream at the moment (probably not cxl related but
> I'm digging). So today I can't boot an x86 machine. (goody)
>
>
> More generally for the flow that would bring the memory up as system ram
> you would typically need the bios to have done the CXL enumeration or
> a bunch of scripts in the kernel to have done it.  In general it can't
> be fully automated, because there are policy decisions to make on things like
> interleaving.
>
> I'm not aware of any open source BIOSs that do it yet.  So you have
> to rely on the same kernel paths as for persistent memory - manual 
> configuration
> etc in the kernel.
>
> There is support in ndctl for those enabling flows, so I'd look there
> for more information
>
> Jonathan
>
>
> >
> >
> > I was expecting the CXL memory to be listed in "System Ram", the lsmem
> > shows only 2G memory which is System RAM, it's not listing the CXL
> > memory.
> >
> > Do I need to pass any particular parameter in the kernel command line?
> >
> > Is there any documentation available? I followed the inputs provided in
> >
> > https://lore.kernel.org/linux-mm/Y+CSOeHVLKudN0A6@kroah.com/T/
> >
> > Is there any documentation/blog listed?
>