[PATCH v3 1/7] arm64: hyperv: Use SMC to detect hypervisor presence

[Wei Liu]

On Fri, Jul 26, 2024 at 03:59:04PM -0700, Roman Kisel wrote:
> The arm64 Hyper-V startup path relies on ACPI to detect
> running under a Hyper-V compatible hypervisor. That
> doesn't work on non-ACPI systems.
> 
> Hoist the ACPI detection logic into a separate function,
> use the new SMC added recently to Hyper-V to use in the
> non-ACPI case.
> 
> Signed-off-by: Roman Kisel <romank at linux.microsoft.com>

The change looks sensible.

Within one minor comment fixed below:

Acked-by: Wei Liu <wei.liu at kernel.org>

However I would also like to get an Acked-by or reivewed-by from someone
who works on the ARM64 side of things -- Saurabh, Boqun, Srivatsa, and
Jinank?

> ---
>  arch/arm64/hyperv/mshyperv.c      | 36 ++++++++++++++++++++++++++-----
>  arch/arm64/include/asm/mshyperv.h |  5 +++++
>  2 files changed, 36 insertions(+), 5 deletions(-)
> 
[...]
> diff --git a/arch/arm64/include/asm/mshyperv.h b/arch/arm64/include/asm/mshyperv.h
> index a975e1a689dd..a7a3586f7cb1 100644
> --- a/arch/arm64/include/asm/mshyperv.h
> +++ b/arch/arm64/include/asm/mshyperv.h
> @@ -51,4 +51,9 @@ static inline u64 hv_get_msr(unsigned int reg)
>  
>  #include <asm-generic/mshyperv.h>
>  
> +#define ARM_SMCCC_VENDOR_HYP_UID_HYPERV_REG_0	0x7948734d
> +#define ARM_SMCCC_VENDOR_HYP_UID_HYPERV_REG_1	0x56726570

Presumably these are ASCII codes for an identifier string, please 
provide comments to explain what they are.

> +#define ARM_SMCCC_VENDOR_HYP_UID_HYPERV_REG_2	0
> +#define ARM_SMCCC_VENDOR_HYP_UID_HYPERV_REG_3	0
> +
>  #endif
> -- 
> 2.34.1
>