Re: [PATCH v3] xen/riscv: identify specific ISA supported by cpu

[Jan Beulich <jbeulich@suse.com>]

On 06.02.2025 14:05, Oleksii Kurochko wrote:
> On 2/5/25 8:07 PM, Conor Dooley wrote:
>> Yo,
>>
>> On Thu, Jan 23, 2025 at 03:46:36PM +0100, Oleksii Kurochko wrote:
>>> Supported ISA extensions are specified in the device tree within the CPU
>>> node, using two properties: `riscv,isa-extensions` and `riscv,isa`.
>>>
>>> Currently, Xen does not support the `riscv,isa-extensions` property, as
>>> all available device tree source (DTS) files in the Linux kernel (v6.12-rc3)
>>> and DTBs generated by QEMU use only the `riscv,isa` property.
>> That's not true? The riscv,isa-extensions property went into linux in
>> late 2023 (6.7 or so) and QEMU in v9.0.0 about a year ago, so all source
>> files in linux and blobs generated by QEMU should have both. OpenSBI &
>> U-Boot support both also. Might not affect your decision about what to
>> support here - but the rationale provided for implementing the deprecated
>> (per the binding at least) property isn't accurate.
> 
> I confused something with Linux kernel sources. Double-check and riscv,isa-extensions
> is really supported.
> 
> Regarding QEMU, at the momemnt, Xen uses Debian bookworm and the following version
> is used:
>    QEMU emulator version 7.2.11 (Debian 1:7.2+dfsg-7+deb12u6)
> 
> I will update the commit message.
> 
> Do you ( Conor and Jan ) think that it makes sense to support deprecated property?
> Or it would be better start to use QEMU v9.0.0 and just drop support for deprecated property?

Unless there's a guarantee that all actual hardware we'd ever run on would
offer the new property, we might be better off supporting both. In no case
should we take only qemu into account, imo.

Jan