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

[Baoquan He <bhe@redhat.com>]

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@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

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
> > 
> > 
>