Re: [PATCH hyperv-next v6 02/11] arm64: hyperv: Use SMCCC to detect hypervisor presence

Roman Kisel
2025-03-17T17:12:54Z

On 3/17/2025 4:37 AM, Mark Rutland wrote:
> On Fri, Mar 14, 2025 at 05:19:22PM -0700, Roman Kisel wrote:

[...]

> The 'acpi_disabled' variable doesn't exist for !CONFIG_ACPI, so its use
> prior to the ifdeffery looks misplaced.
>
> Usual codestyle is to avoid ifdeffery if possible, using IS_ENABLED().
> Otherwise, use a stub, e.g.
>

That looks much better, thanks for the review! Will implement in
the next version.

> | #ifdef CONFIG_ACPI
> | static bool __init hyperv_detect_via_acpi(void)
> | {
> | if (acpi_disabled)
> | return false;
> |
> | if (acpi_gbl_FADT.header.revision < 6)
> | return false;
> |
> | return strncmp((char *)&acpi_gbl_FADT.hypervisor_id, "MsHyperV", 8) == 0;
> | }
> | #else
> | static inline bool hyperv_detect_via_acpi(void) { return false; }
> | #endif
>
> Mark.
>
>> +static bool __init hyperv_detect_via_smccc(void)
>> +{
>> + uuid_t hyperv_uuid = UUID_INIT(
>> + 0x4d32ba58, 0x4764, 0xcd24,
>> + 0x75, 0x6c, 0xef, 0x8e,
>> + 0x24, 0x70, 0x59, 0x16);
>> +
>> + return arm_smccc_hyp_present(&hyperv_uuid);
>> +}
>> +
>> static int __init hyperv_init(void)
>> {
>> struct hv_get_vp_registers_output result;
>> @@ -35,13 +70,11 @@ static int __init hyperv_init(void)
>>
>> /*
>> * Allow for a kernel built with CONFIG_HYPERV to be running in
>> - * a non-Hyper-V environment, including on DT instead of ACPI.
>> + * a non-Hyper-V environment.
>> + *
>> * In such cases, do nothing and return success.
>> */
>> - if (acpi_disabled)
>> - return 0;
>> -
>> - if (strncmp((char *)&acpi_gbl_FADT.hypervisor_id, "MsHyperV", 8))
>> + if (!hyperv_detect_via_acpi() && !hyperv_detect_via_smccc())
>> return 0;
>>
>> /* Setup the guest ID */
>> --
>> 2.43.0
>>

--
Thank you,
Roman