Re: [PATCH] arm64: kvm, smccc: Fix vendor uuid

[Roman Kisel]

On 7/21/2025 9:15 AM, Sudeep Holla wrote:
> (I can't see this original patch in my mailbox, got only Marc's response)
>
> On Mon, Jul 21, 2025 at 02:05:58PM +0100, Jack Thomson wrote:
> > From: Jack Thomson <jackabt@xxxxxxxxxx>
> >
> > Commit 13423063c7cb ("arm64: kvm, smccc: Introduce and use API for
> > getting hypervisor UUID") replaced the explicit register constants
> > with the UUID_INIT macro. However, there is an endian issue, meaning
> > the UUID generated and used in the handshake didn't match UUID prior to
> > the commit.
> >
> > The change in UUID causes the SMCCC vendor handshake to fail with older
> > guest kernels, meaning devices such as PTP were not available in the
> > guest.
> >
> > This patch updates the parameters to the macro to generate a UUID which
> > matches the previous value, and re-establish backwards compatibility
> > with older guest kernels.
>
> Nice catch. This is result of classic confusion with UUID and GUID especially
> coming from Microsoft who tend to use GUID more.
>
> Reviewed-by: Sudeep Holla <sudeep.holla@xxxxxxx>
>
> This also makes me wonder if the initialisation in arch/arm64/hyperv/mshyperv.c
> is also wrong or may be that's correct only MS guys can confirm as I couldn't
> find the UUID string for that.

MUCH appreciated!! Apologies for that miss in testing of the older
kernels. I'll check on our side and will fix what needs fixing.

>

--
Thank you,
Roman