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

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Date: Tue, 11 Jun 2024 07:55:27 -0700
From: Roman Kisel <romank@...ux.microsoft.com>
To: Elliot Berman <quic_eberman@...cinc.com>
Cc: arnd@...db.de, bhelgaas@...gle.com, bp@...en8.de,
 catalin.marinas@....com, dave.hansen@...ux.intel.com, decui@...rosoft.com,
 haiyangz@...rosoft.com, hpa@...or.com, kw@...ux.com, kys@...rosoft.com,
 lenb@...nel.org, lpieralisi@...nel.org, mingo@...hat.com,
 mhklinux@...look.com, rafael@...nel.org, robh@...nel.org,
 tglx@...utronix.de, wei.liu@...nel.org, will@...nel.org,
 linux-acpi@...r.kernel.org, linux-arch@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-hyperv@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org, x86@...nel.org,
 ssengar@...rosoft.com, sunilmut@...rosoft.com, vdso@...bites.dev
Subject: Re: [PATCH v2 1/6] arm64/hyperv: Support DeviceTree


On 5/16/2024 8:27 AM, Roman Kisel wrote:
> 
> 
> 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.
> 
We have that now. Will send out the revised patches sometime during the 
next week most likely.

>>>
>>> Signed-off-by: Roman Kisel <romank@...ux.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@...ts.infradead.org
>>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

-- 
Thank you,
Roman

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