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

Roman Kisel
2024-05-16T15:27:18Z

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@kernel.org/
> [2]: https://lore.kernel.org/all/20240222-gunyah-v17-4-1e9da6763d38@quicinc.com/

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

>>
>> 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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>> linux-arm-kernel@lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

--
Thank you,
Roman