On 3/19/2025 3:11 PM, Michael Kelley wrote:
From: Mark Rutland <mark.rutland@xxxxxxx> Sent: Monday, March 17, 2025 4:38 AM
The 'acpi_disabled' variable doesn't exist for !CONFIG_ACPI, so its use
prior to the ifdeffery looks misplaced.
FWIW, include/linux/acpi.h has
#define acpi_disabled 1
when !CONFIG_ACPI. But I agree that using a stub is better.
Thanks, Michael! I didn't "fact-checked" what was suggested indeed.
Agreed that the stub makes the code look better.
Michael
Usual codestyle is to avoid ifdeffery if possible, using IS_ENABLED().
Otherwise, use a stub, e.g.
| #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
