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

Easwar Hariharan
2025-03-07T21:55:25Z

On 3/7/2025 1:36 PM, Nuno Das Neves wrote:
> On 3/6/2025 11:05 AM, Michael Kelley wrote:
>> From: Nuno Das Neves <nunodasneves@linux.microsoft.com> Sent: Thursday, February 27, 2025 4:21 PM
>>>
>>> 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.
>>
>> I was trying to remember if there was some reason I originally put
>> hv_do_hypercall() and hv_do_fast_hypercall8() in the .c file instead of
>> the header like on x86. But I don't remember a reason. During
>> development, the code changed several times, and there might have
>> been a reason that didn't persistent in the version that was finally
>> accepted upstream.
>>
>> My only comment is that hv_do_hypercall() and the 8 and 16 "fast"
>> versions should probably stay together one place on the arm64 side,
>> even if it doesn't match x86.
>>
>
> I think I'll just keep them together here for now then. They
> could be moved to the header in future if it seems worth doing.
>

I was really hoping the answer here would be to move all of them together to the header,
but oh well.

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