| Message ID | 20250414224713.1866095-3-romank@linux.microsoft.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | arm64: hyperv: Support Virtual Trust Level Boot | expand |
From: Roman Kisel <romank@linux.microsoft.com> Sent: Monday, April 14, 2025 3:47 PM > > 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. Then > use the vendor-specific hypervisor service call (implemented > recently in Hyper-V) via SMCCC in the non-ACPI case. > > Signed-off-by: Roman Kisel <romank@linux.microsoft.com> > --- > arch/arm64/hyperv/mshyperv.c | 50 ++++++++++++++++++++++++++++++++---- > 1 file changed, 45 insertions(+), 5 deletions(-) > > diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c > index 4e27cc29c79e..21458b6338aa 100644 > --- a/arch/arm64/hyperv/mshyperv.c > +++ b/arch/arm64/hyperv/mshyperv.c > @@ -28,6 +28,48 @@ int hv_get_hypervisor_version(union > hv_hypervisor_version_info *info) > } > EXPORT_SYMBOL_GPL(hv_get_hypervisor_version); > > +#ifdef CONFIG_ACPI > + > +static bool __init hyperv_detect_via_acpi(void) > +{ > + if (acpi_disabled) > + return false; > + /* > + * Hypervisor ID is only available in ACPI v6+, and the > + * structure layout was extended in v6 to accommodate that > + * new field. > + * > + * At the very minimum, this check makes sure not to read > + * past the FADT structure. > + * > + * It is also needed to catch running in some unknown > + * non-Hyper-V environment that has ACPI 5.x or less. > + * In such a case, it can't be Hyper-V. > + */ > + if (acpi_gbl_FADT.header.revision < 6) > + return false; > + return strncmp((char *)&acpi_gbl_FADT.hypervisor_id, "MsHyperV", 8) == 0; > +} > + > +#else > + > +static bool __init hyperv_detect_via_acpi(void) > +{ > + return false; > +} > + > +#endif > + > +static bool __init hyperv_detect_via_smccc(void) > +{ > + uuid_t hyperv_uuid = UUID_INIT( > + 0x58ba324d, 0x6447, 0x24cd, > + 0x75, 0x6c, 0xef, 0x8e, > + 0x24, 0x70, 0x59, 0x16); I had previously given my Reviewed-by: on v5 of this patch. But looking at it again, it would be nice if this UUID were defined in include/linux/arm-smccc.h alongside the definition of ARM_SMCCC_VENDOR_HYP_UID_KVM. The UUID values are are independent of each other, but it's a bit asymmetric to have the KVM UUID defined centrally while the Hyper-V UUID is buried in Hyper-V specific code. But I'm OK with the current code if there's nothing else to respin for. > + > + return arm_smccc_hypervisor_has_uuid(&hyperv_uuid); > +} > + > static int __init hyperv_init(void) > { > struct hv_get_vp_registers_output result; > @@ -36,13 +78,11 @@ 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 > My UUID comment notwithstanding, Reviewed-by: Michael Kelley <mhklinux@outlook.com>
diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c index 4e27cc29c79e..21458b6338aa 100644 --- a/arch/arm64/hyperv/mshyperv.c +++ b/arch/arm64/hyperv/mshyperv.c @@ -28,6 +28,48 @@ int hv_get_hypervisor_version(union hv_hypervisor_version_info *info) } EXPORT_SYMBOL_GPL(hv_get_hypervisor_version); +#ifdef CONFIG_ACPI + +static bool __init hyperv_detect_via_acpi(void) +{ + if (acpi_disabled) + return false; + /* + * Hypervisor ID is only available in ACPI v6+, and the + * structure layout was extended in v6 to accommodate that + * new field. + * + * At the very minimum, this check makes sure not to read + * past the FADT structure. + * + * It is also needed to catch running in some unknown + * non-Hyper-V environment that has ACPI 5.x or less. + * In such a case, it can't be Hyper-V. + */ + if (acpi_gbl_FADT.header.revision < 6) + return false; + return strncmp((char *)&acpi_gbl_FADT.hypervisor_id, "MsHyperV", 8) == 0; +} + +#else + +static bool __init hyperv_detect_via_acpi(void) +{ + return false; +} + +#endif + +static bool __init hyperv_detect_via_smccc(void) +{ + uuid_t hyperv_uuid = UUID_INIT( + 0x58ba324d, 0x6447, 0x24cd, + 0x75, 0x6c, 0xef, 0x8e, + 0x24, 0x70, 0x59, 0x16); + + return arm_smccc_hypervisor_has_uuid(&hyperv_uuid); +} + static int __init hyperv_init(void) { struct hv_get_vp_registers_output result; @@ -36,13 +78,11 @@ 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 */
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. Then use the vendor-specific hypervisor service call (implemented recently in Hyper-V) via SMCCC in the non-ACPI case. Signed-off-by: Roman Kisel <romank@linux.microsoft.com> --- arch/arm64/hyperv/mshyperv.c | 50 ++++++++++++++++++++++++++++++++---- 1 file changed, 45 insertions(+), 5 deletions(-)