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

Nuno Das Neves
2025-02-28T00:21:15Z

On 2/26/2025 9:56 PM, Easwar Hariharan wrote:
> 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*
>
>
Thanks!

>> 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.
>
Good point, I don't see a good reason this can't be in the header.

>> /*
>> * 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
>
Good point, missed that one...

>> +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?
>
Yes I wondered about that warning. That's true, if I just put it in the arm64 header
then this won't be needed at all, so I might just do that!

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