NAK: [PATCH v2 0/3][f/j/l/m linux] UBUNTU: SAUCE: (no-up) hv: Fix supply vendor ID

[Tim Gardner]

On 9/20/23 1:08 AM, Stefan Bader wrote:
> On 19.09.23 15:59, Tim Gardner wrote:
>> BugLink: https://bugs.launchpad.net/bugs/2036600
>>
>> SRU Justification
>>
>> [Impact]
>>
>> The linux-azure 6.2 kernel doesn't report a correct GUEST_ID
>>
>> There is a mistake in the commit 
>> (https://git.launchpad.net/~canonical-kernel/ubuntu/+source/linux-azure/+git/jammy/commit/?id=5dd24f2df3280d4354641f4687dbb36e418e7de8) :
>>
> 
> Hm when the mistake is in an azure commit, why do we fix this with SAUCE 
> in every distro kernel?
> 

There are some customers that run the generic kernel instead of the 
Azure tuned kernel (though I don't know why).

I have a comment from Dexuan Cui (Microsoft) that only 6.2 and newer 
have this issue. I'll re-issue this patch with the correct subject.

rtg
> 
>> Before the commit, the good guest_id is 0x8180000602100000.
>>
>> With the commit, the generated guest_id is incorrect: 
>> 0x0080000602100000, i.e. the 0x81 from bit 56~63 are dropped.
>>
>> See "include/asm-generic/hyperv-tlfs.h" for the definition of the bits:
>> * Bit(s)
>> * 63 - Indicates if the OS is Open Source or not; 1 is Open Source
>>
>> * 62:56 - Os Type; Linux is 0x100 !!!!! Dexuan: this should be 0x1. 
>> I'll post a patch to LKML to fix this typo.
>>
>> * 55:48 - Distro specific identification
>> * 47:16 - Linux kernel version number
>> * 15:0 - Distro specific identification
>>
>> See 
>> https://learn.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/tlfs ("February, 2020: Released Version 6.0b", page 15)
>>
>> As a result, the host thinks that the VM is not an open-source OS, and 
>> it's not Linux. Consequently, the "VM Availability" fron Azure portal 
>> is 0 (unhealthy): some users rely on the info to manage their VMs, 
>> e.g. if the VM is erroneously reported "unhealthy", the VM may be 
>> killed and re-created, and the new VM is still "unhealthy", and the VM 
>> may be killed and re-created again...
>>
>> Please consider integrating the below fix ASAP. This affects regular 
>> VMs, and I think this affects CVMs as well.
>>
>> The fix should be:
>>
>> diff --git a/include/asm-generic/hyperv-tlfs.h 
>> b/include/asm-generic/hyperv-tlfs.h
>> @@ -135,7 +135,7 @@ union hv_reference_tsc_msr {
>> *
>> */
>>
>> -#define HV_LINUX_VENDOR_ID 0x80 /* Canonical */
>> +#define HV_LINUX_VENDOR_ID 0x8180 /* Canonical */
>>
>> [Test Plan]
>>
>> Microsoft tested
>>
>> [Regression Potential]
>>
>> This (incorrect) patch has been in place for 10 years. Its possible 
>> that some consumers have come to rely on this VM identifier.
>> I am reluctant to fix the ESM kernels for that very reason, plus 
>> nobody has ever complained about an incorrect vendor ID.
>>
>> [Other Info]
>>
>> SF: #00368936
>>
>>
> 

-- 
-----------
Tim Gardner
Canonical, Inc