Re: [PATCH v2 1/6] arm64/hyperv: Support DeviceTree

[Roman Kisel <romank@xxxxxxxxxxxxxxxxxxx>]

On 5/15/2024 3:02 PM, Elliot Berman wrote:
> On Tue, May 14, 2024 at 03:43:48PM -0700, Roman Kisel wrote:
> > The Virtual Trust Level platforms rely on DeviceTree, and the
> > arm64/hyperv code supports ACPI only. Update the logic to
> > support DeviceTree on boot as well as ACPI.
>
> Could you use Call UID query from SMCCC? KVM [1] and Gunyah [2] have
> been using this to identify if guest is running under those respective
> hypervisors. This works in both DT and ACPI cases.
>
> [1]: https://lore.kernel.org/all/20210330145430.996981-2-maz@xxxxxxxxxx/
> [2]: https://lore.kernel.org/all/20240222-gunyah-v17-4-1e9da6763d38@xxxxxxxxxxx/

That would be very neat indeed, thanks! Talking to the hypervisor folks.

> > Signed-off-by: Roman Kisel <romank@xxxxxxxxxxxxxxxxxxx>
> > ---
> >   arch/arm64/hyperv/mshyperv.c | 34 +++++++++++++++++++++++++++++-----
> >   1 file changed, 29 insertions(+), 5 deletions(-)
> >
> > diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c
> > index b1a4de4eee29..208a3bcb9686 100644
> > --- a/arch/arm64/hyperv/mshyperv.c
> > +++ b/arch/arm64/hyperv/mshyperv.c
> > @@ -15,6 +15,9 @@
> >   #include <linux/errno.h>
> >   #include <linux/version.h>
> >   #include <linux/cpuhotplug.h>
> > +#include <linux/libfdt.h>
> > +#include <linux/of.h>
> > +#include <linux/of_fdt.h>
> >   #include <asm/mshyperv.h>
> >   
> >   static bool hyperv_initialized;
> > @@ -27,6 +30,29 @@ int hv_get_hypervisor_version(union hv_hypervisor_version_info *info)
> >   	return 0;
> >   }
> >   
> > +static bool hyperv_detect_fdt(void)
> > +{
> > +#ifdef CONFIG_OF
> > +	const unsigned long hyp_node = of_get_flat_dt_subnode_by_name(
> > +			of_get_flat_dt_root(), "hypervisor");
> > +
> > +	return (hyp_node != -FDT_ERR_NOTFOUND) &&
> > +			of_flat_dt_is_compatible(hyp_node, "microsoft,hyperv");
> > +#else
> > +	return false;
> > +#endif
> > +}
> > +
> > +static bool hyperv_detect_acpi(void)
> > +{
> > +#ifdef CONFIG_ACPI
> > +	return !acpi_disabled &&
> > +			!strncmp((char *)&acpi_gbl_FADT.hypervisor_id, "MsHyperV", 8);
> > +#else
> > +	return false;
> > +#endif
> > +}
> > +
> >   static int __init hyperv_init(void)
> >   {
> >   	struct hv_get_vp_registers_output	result;
> > @@ -35,13 +61,11 @@ 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_fdt() && !hyperv_detect_acpi())
> >   		return 0;
> >   
> >   	/* Setup the guest ID */
> > --
> > 2.45.0
> >
> >
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

--
Thank you,
Roman