linux-kernel - Re: [PATCH hyperv-next 0/2] x86/hyperv: VTL mode reboot fixes

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Message-ID: <e39b1947-0ea6-4573-9b71-7c8ea6c96d8c@linux.microsoft.com>
Date: Wed, 12 Feb 2025 14:56:43 -0800
From: Roman Kisel <romank@...ux.microsoft.com>
To: Saurabh Singh Sengar <ssengar@...ux.microsoft.com>,
 Wei Liu <wei.liu@...nel.org>
Cc: bp@...en8.de, dave.hansen@...ux.intel.com, decui@...rosoft.com,
 haiyangz@...rosoft.com, hpa@...or.com, kys@...rosoft.com, mingo@...hat.com,
 tglx@...utronix.de, linux-hyperv@...r.kernel.org,
 linux-kernel@...r.kernel.org, x86@...nel.org, apais@...rosoft.com,
 benhill@...rosoft.com, sunilmut@...rosoft.com, vdso@...bites.dev
Subject: Re: [PATCH hyperv-next 0/2] x86/hyperv: VTL mode reboot fixes



On 2/12/2025 9:54 AM, Saurabh Singh Sengar wrote:
> On Wed, Feb 12, 2025 at 02:21:18AM +0000, Wei Liu wrote:
[...]
>>
>> Saurabh please review these patches. Thanks.
> 
> Hi Roman,
Hi Saurabh,

> 
> Thanks for the patch, few suggestions and queries:
> 
> 1. Please fix the kernel bot warning
Will do!

> 2. Cc Stable tree is not enough, you need to mention the "Fixes" tag as well
>     for the commit upto where you want this patch to be backported.
Understood, thanks!

> 3. In your 2/2 commit, you mention 'triple fault' is the only way to reboot in x86.
>     Is that accurate ? Do you mean to say OpenHCL/VTL here ?
>     If this behaviour is specific to OpenHCl and not VTLs in general, is there a way
>     we can make these changes only for OpenHCL.
Right, I meant OpenHCL/VTL2, thank you very much! The changes are scoped
to running in VTLs in general at the moment. I can add a check for the
VTL == 2 if you'd like me to.

For VTL1 (aka LVBS), maybe folks would like to do something else,
do you happen to know? Maybe to report that to the VTL0 guest kernel
although seems dubious: the higher VTL failed so the lights must be out
for the lower VTLs? Or kexec?

>     
> 
> - Saurabh
> 
>>
>> I don't have a strong opinion on them.
>>
>>>
>>>   arch/x86/hyperv/hv_vtl.c | 31 +++++++++++++++++++++++++++++++
>>>   1 file changed, 31 insertions(+)
>>>
>>>
>>> base-commit: 2e03358be78b65d28b66e17aca9e0c8700b0df78
>>> -- 
>>> 2.34.1
>>>

-- 
Thank you,
Roman