Re: [Qemu-riscv] RISC-V: qemu should provide different "model" strings in DT for RV64 and RV32

[Palmer Dabbelt]

On Mon, 06 May 2019 12:52:32 PDT (-0700), Alistair Francis wrote:
> On Mon, 2019-05-06 at 20:53 +0200, Karsten Merker wrote:
> > On Mon, May 06, 2019 at 02:33:29PM +0000, Alistair Francis wrote:
> > > On Sun, 2019-05-05 at 23:03 +0200, Karsten Merker wrote:
> > > > Hello,
> > > > 
> > > > while working on RISC-V support for the Debian flash-kernel packa
> > > > 
> > > > I have stumbled over a potential problem with the "model" string
> > > > that qemu sets in the DT that it generates for the "virt"
> > > > machine,
> > > > namely "riscv-virtio,qemu".
> > > > 
> > > > Some tools, among them flash-kernel, use the "model" string to
> > > > determine on which specific type of hardware they are running and
> > > > perform corresponding hardware-specific actions.  It looks like
> > > > qemu uses the same model string for both RV64 and RV32, which
> > > > makes it impossible to differentiate between the two. I would
> > > > therefore like to propose to make the model-string
> > > > XLEN-dependent, i.e. "riscv64-virtio,qemu" respectively
> > > > "riscv32-virtio,qemu".
> > > 
> > > This sounds fine to me.
> > > 
> > > Is there anything that already relies on the
> > > "riscv-virtio,qemu" compat string?
> >
> > At least nothing that I am aware of.
> >
> > > Maybe we can keep that and add a 32/64 bit one so we don't
> > > break anything that is already working.
> >
> > AFAICS this isn't possible as according to the device-tree
> > specification the "model" property in DT can only have a single
> > value:
> >
> >   Property name: model
> >   Value type: <string>
> >
> > To allow for multiple values that would have to be
> >
> >   Value type: <stringlist>
>
> Ah, no worries. I think it's worth sending the patch. The 4.1
> development cycle has just opened so now seems like a good time to send
> it. We can then test to make sure nothing is broken before the next
> release.

I'd be OK with the change from "riscv-virtio,qemu" to "riscv64-virtio,qemu".
It's nominally an interface change, but I doubt anyone would be using it.  It's
probably best to check on sw-dev just to be sure.

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