[PATCHv6 00/16] x86/tdx: Add kexec support

[Nikolay Borisov]

On 31.01.24 г. 14:47 ч., Baoquan He wrote:
> On 01/31/24 at 09:31am, Nikolay Borisov wrote:
>>
>>
>> On 30.01.24 г. 15:43 ч., Paolo Bonzini wrote:
>>> On 1/24/24 13:55, Kirill A. Shutemov wrote:
>>>> The patchset adds bits and pieces to get kexec (and crashkernel) work on
>>>> TDX guest.
>>>>
>>>> The last patch implements CPU offlining according to the approved ACPI
>>>> spec change poposal[1]. It unlocks kexec with all CPUs visible in
>>>> the target
>>>> kernel. It requires BIOS-side enabling. If it missing we fallback to
>>>> booting
>>>> 2nd kernel with single CPU.
>>>>
>>>> Please review. I would be glad for any feedback.
>>>
>>> Hi Kirill,
>>>
>>> I have a very basic question: is there a reason why this series does not
>>> revert commit cb8eb06d50fc, "x86/virt/tdx: Disable TDX host support when
>>> kexec is enabled"?
>>
>> While on the topic, Paolo do you think it's  better to have a runtime
>> disable of kexec rather than at compile time:
>>
>> [RFC PATCH] x86/virt/tdx: Disable KEXEC in the presence of TDX
>>
>> 20240118160118.1899299-1-nik.borisov at suse.com
> 
> Runtime disabling kexec looks better than at cmpile time, esp for
> distros. While from above patch, making using of kexec_load_disabled to
> achive the runtime disabling may not be so good. Because we have a front
> door to enable it through:
> 
> /proc/sys/kernel/kexec_load_disabled

AFAIU it can't be enabled via this sysctl because the handler for it 
expects only 1 to be written to it:

      2                 .proc_handler   = proc_dointvec_minmax, 

      1                 .extra1         = SYSCTL_ONE, 

   994                  .extra2         = SYSCTL_ONE,

> 
> If there's a flag or status to check if TDX host is enabled, and does
> the checking in kexec_load_permitted(), that could be better. Anyway, I
> saw Huang, Kai has posted the tdx host support patchset.
> 
>>
>> I'm trying to get traction for this patch.
>>
>>
>>>
>>> Thanks,
>>>
>>> Paolo
>>>
>>>
>>
>