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

From: Roman Kisel <romank@linux.microsoft.com>
To: Elliot Berman <quic_eberman@quicinc.com>
Cc: arnd@arndb.de, bhelgaas@google.com, bp@alien8.de,
	catalin.marinas@arm.com, dave.hansen@linux.intel.com,
	decui@microsoft.com, haiyangz@microsoft.com, hpa@zytor.com,
	kw@linux.com, kys@microsoft.com, lenb@kernel.org,
	lpieralisi@kernel.org, mingo@redhat.com, mhklinux@outlook.com,
	rafael@kernel.org, robh@kernel.org, tglx@linutronix.de,
	wei.liu@kernel.org, will@kernel.org, linux-acpi@vger.kernel.org,
	linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-pci@vger.kernel.org, x86@kernel.org, ssengar@microsoft.com,
	sunilmut@microsoft.com, vdso@hexbites.dev
Subject: Re: [PATCH v2 1/6] arm64/hyperv: Support DeviceTree
Date: Thu, 16 May 2024 08:27:12 -0700	[thread overview]
Message-ID: <9b216f16-a2ea-48d7-8986-f0c2e3f3d009@linux.microsoft.com> (raw)
In-Reply-To: <20240515143359142-0700.eberman@hu-eberman-lv.qualcomm.com>

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

-- 
Thank you,
Roman