Re: [PATCH v5 03/10] arm64/hyperv: Add some missing functions to arm64

Easwar Hariharan
2025-02-27T05:57:00Z

On 2/26/2025 3:07 PM, Nuno Das Neves wrote:
> These non-nested msr and fast hypercall functions are present in x86,
> but they must be available in both architetures for the root partition

nit: *architectures*

> driver code.
>
> Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
> ---
> arch/arm64/hyperv/hv_core.c | 17 +++++++++++++++++
> arch/arm64/include/asm/mshyperv.h | 12 ++++++++++++
> include/asm-generic/mshyperv.h | 2 ++
> 3 files changed, 31 insertions(+)
>
> diff --git a/arch/arm64/hyperv/hv_core.c b/arch/arm64/hyperv/hv_core.c
> index 69004f619c57..e33a9e3c366a 100644
> --- a/arch/arm64/hyperv/hv_core.c
> +++ b/arch/arm64/hyperv/hv_core.c
> @@ -53,6 +53,23 @@ u64 hv_do_fast_hypercall8(u16 code, u64 input)
> }
> EXPORT_SYMBOL_GPL(hv_do_fast_hypercall8);
>
> +/*
> + * hv_do_fast_hypercall16 -- Invoke the specified hypercall
> + * with arguments in registers instead of physical memory.
> + * Avoids the overhead of virt_to_phys for simple hypercalls.
> + */
> +u64 hv_do_fast_hypercall16(u16 code, u64 input1, u64 input2)
> +{
> + struct arm_smccc_res res;
> + u64 control;
> +
> + control = (u64)code | HV_HYPERCALL_FAST_BIT;
> +
> + arm_smccc_1_1_hvc(HV_FUNC_ID, control, input1, input2, &res);
> + return res.a0;
> +}
> +EXPORT_SYMBOL_GPL(hv_do_fast_hypercall16);
> +

I'd like this to have been in arch/arm64/include/asm/mshyperv.h like its x86
counterpart, but that's just my personal liking of symmetry. I see why it's here
with its slow and 8-byte brethren.

> /*
> * Set a single VP register to a 64-bit value.
> */
> diff --git a/arch/arm64/include/asm/mshyperv.h b/arch/arm64/include/asm/mshyperv.h
> index 2e2f83bafcfb..2a900ba00622 100644
> --- a/arch/arm64/include/asm/mshyperv.h
> +++ b/arch/arm64/include/asm/mshyperv.h
> @@ -40,6 +40,18 @@ static inline u64 hv_get_msr(unsigned int reg)
> return hv_get_vpreg(reg);
> }
>
> +/*
> + * Nested is not supported on arm64
> + */
> +static inline void hv_set_non_nested_msr(unsigned int reg, u64 value)
> +{
> + hv_set_msr(reg, value);
> +}

empty line preferred here, also reported by checkpatch

> +static inline u64 hv_get_non_nested_msr(unsigned int reg)
> +{
> + return hv_get_msr(reg);
> +}
> +
> /* SMCCC hypercall parameters */
> #define HV_SMCCC_FUNC_NUMBER 1
> #define HV_FUNC_ID ARM_SMCCC_CALL_VAL( \
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index c020d5d0ec2a..258034dfd829 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -72,6 +72,8 @@ extern void * __percpu *hyperv_pcpu_output_arg;
>
> extern u64 hv_do_hypercall(u64 control, void *inputaddr, void *outputaddr);
> extern u64 hv_do_fast_hypercall8(u16 control, u64 input8);
> +extern u64 hv_do_fast_hypercall16(u16 control, u64 input1, u64 input2);
> +

checkpatch warns against putting externs in header files, and FWIW, if hv_do_fast_hypercall16()
for arm64 were in arch/arm64/include/asm/mshyperv.h like its x86 counterpart, you probably
wouldn't need this?

> bool hv_isolation_type_snp(void);
> bool hv_isolation_type_tdx(void);
>