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

[Roman Kisel <romank@linux.microsoft.com>]

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@amazon.com>
>>
>> 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@arm.com>
> 
> 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