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

Elliot Berman
2024-05-15T22:04:20Z

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@kernel.org/
[2]: https://lore.kernel.org/all/20240222-gunyah-v17-4-1e9da6763d38@quicinc.com/
>
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
> ---
> 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
>
>
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