On Fri, Jul 26, 2024 at 03:59:04PM -0700, Roman Kisel wrote: > The arm64 Hyper-V startup path relies on ACPI to detect > running under a Hyper-V compatible hypervisor. That > doesn't work on non-ACPI systems. > > Hoist the ACPI detection logic into a separate function, > use the new SMC added recently to Hyper-V to use in the > non-ACPI case. > > Signed-off-by: Roman Kisel <romank@xxxxxxxxxxxxxxxxxxx> > --- > arch/arm64/hyperv/mshyperv.c | 36 ++++++++++++++++++++++++++----- > arch/arm64/include/asm/mshyperv.h | 5 +++++ > 2 files changed, 36 insertions(+), 5 deletions(-) > > diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c > index b1a4de4eee29..341f98312667 100644 > --- a/arch/arm64/hyperv/mshyperv.c > +++ b/arch/arm64/hyperv/mshyperv.c > @@ -27,6 +27,34 @@ int hv_get_hypervisor_version(union hv_hypervisor_version_info *info) > return 0; > } > > +static bool hyperv_detect_via_acpi(void) > +{ > + if (acpi_disabled) > + return false; > +#if IS_ENABLED(CONFIG_ACPI) > + /* Hypervisor ID is only available in ACPI v6+. */ > + if (acpi_gbl_FADT.header.revision < 6) > + return false; > + return strncmp((char *)&acpi_gbl_FADT.hypervisor_id, "MsHyperV", 8) == 0; > +#else > + return false; > +#endif > +} > + > +static bool hyperv_detect_via_smc(void) > +{ > + struct arm_smccc_res res = {}; > + > + if (arm_smccc_1_1_get_conduit() != SMCCC_CONDUIT_HVC) > + return false; > + arm_smccc_1_1_hvc(ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID, &res); > + > + return res.a0 == ARM_SMCCC_VENDOR_HYP_UID_HYPERV_REG_0 && > + res.a1 == ARM_SMCCC_VENDOR_HYP_UID_HYPERV_REG_1 && > + res.a2 == ARM_SMCCC_VENDOR_HYP_UID_HYPERV_REG_2 && > + res.a3 == ARM_SMCCC_VENDOR_HYP_UID_HYPERV_REG_3; > +} As you mentioned in the cover letter this is supported in latest Hyper-V hypervisor, can we add a comment about it, specifying the exact version in it would be great. If someone attempts to build non-ACPI kernel on older Hyper-V what is the behaviour of this function, do we need to safeguard or handle that case ? - Saurabh