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

[Roman Kisel]

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