linux-kernel - Re: [PATCH hyperv-next v5 06/11] arm64, x86: hyperv: Report the VTL the system boots in

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Message-ID: <2342dda1-2976-4506-ab68-640739a1bd5b@linux.microsoft.com>
Date: Mon, 10 Mar 2025 09:42:15 -0700
From: Roman Kisel <romank@...ux.microsoft.com>
To: Wei Liu <wei.liu@...nel.org>
Cc: arnd@...db.de, bhelgaas@...gle.com, bp@...en8.de,
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Subject: Re: [PATCH hyperv-next v5 06/11] arm64, x86: hyperv: Report the VTL
 the system boots in



On 3/9/2025 5:31 PM, Wei Liu wrote:
> On Fri, Mar 07, 2025 at 02:02:58PM -0800, Roman Kisel wrote:
>> The hyperv guest code might run in various Virtual Trust Levels.
>>
>> Report the level when the kernel boots in the non-default (0)
>> one.
>>
>> Signed-off-by: Roman Kisel <romank@...ux.microsoft.com>
>> ---
>>   arch/arm64/hyperv/mshyperv.c | 2 ++
>>   arch/x86/hyperv/hv_vtl.c     | 2 +-
>>   2 files changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c
>> index a7db03f5413d..3bc16dbee758 100644
>> --- a/arch/arm64/hyperv/mshyperv.c
>> +++ b/arch/arm64/hyperv/mshyperv.c
>> @@ -108,6 +108,8 @@ static int __init hyperv_init(void)
>>   	if (ms_hyperv.priv_high & HV_ACCESS_PARTITION_ID)
>>   		hv_get_partition_id();
>>   	ms_hyperv.vtl = get_vtl();
>> +	if (ms_hyperv.vtl > 0) /* non default VTL */
> 
> "non-default".
> 

Thanks, will fix that!

>> +		pr_info("Linux runs in Hyper-V Virtual Trust Level %d\n", ms_hyperv.vtl);
>>   
>>   	ms_hyperv_late_init();
>>   
>> diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
>> index 4e1b1e3b5658..c21bee7e8ff3 100644
>> --- a/arch/x86/hyperv/hv_vtl.c
>> +++ b/arch/x86/hyperv/hv_vtl.c
>> @@ -24,7 +24,7 @@ static bool __init hv_vtl_msi_ext_dest_id(void)
>>   
>>   void __init hv_vtl_init_platform(void)
>>   {
>> -	pr_info("Linux runs in Hyper-V Virtual Trust Level\n");
>> +	pr_info("Linux runs in Hyper-V Virtual Trust Level %d\n", ms_hyperv.vtl);
> 
> Where isn't there a check for ms_hyperv.vtl > 0 here?
> 

On x86, there is

#ifdef CONFIG_HYPERV_VTL_MODE
void __init hv_vtl_init_platform(void);
int __init hv_vtl_early_init(void);
#else
static inline void __init hv_vtl_init_platform(void) {}
static inline int __init hv_vtl_early_init(void) { return 0; }
#endif

> Please be consistent across different architectures.
> 

In the earlier versions of the patch series, I had that piece
from the above mirrored in the arm64, and there was advice on
removing the function as it contained just one statement.
I'll revisit the approach, thanks for your help!

>>   
>>   	x86_platform.realmode_reserve = x86_init_noop;
>>   	x86_platform.realmode_init = x86_init_noop;
>> -- 
>> 2.43.0
>>
>>

-- 
Thank you,
Roman