Re: [RFC PATCH v3 01/27] x86/apic: Propagate APIC_SPIV writes to hv for Secure AVIC

[Naveen N Rao <naveen@kernel.org>]

On Thu, Jul 09, 2026 at 07:03:49PM -0700, Borislav Petkov wrote:
> On Wed, Jul 08, 2026 at 12:01:59PM +0530, Naveen N Rao (AMD) wrote:
> > From: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
> > 
> > Hypervisor needs to be aware of the VAPIC's APIC_SPIV state for
> > LVT masking/unmasking. So, propagate the guest's APIC_SPIV
> > writes to the hypervisor.
> > 
> > Fixes: c822f58a4fab ("x86/apic: Populate .read()/.write() callbacks of Secure AVIC driver")
> 
> What is that patch actually fixing?

Guest doesn't boot without this change.

> 
> Does it need to go to stable?

Yes. I will tag stable on this.

> 
> SPIV needs to be masked and unmasked by the guest?
> 
> Doesn't seem too earth-shattering to me but what do I know...

APIC_SPIV has a bit to (soft-)disable the APIC. It starts off disabled 
and the kernel has to write to it to enable the APIC. If writes from the 
guest are not propagated to KVM, KVM does not deliver interrupts to the 
guest since the APIC is disabled as far as it is concerned.

I will update the commit log with these details.

> 
> > Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
> 
> verify_tags: WARNING: Sender ["Naveen N Rao (AMD)" <naveen@kernel.org>] hasn't signed off on the patch!
> 
> When you send someone else's patch, you *must* put you SOB after hers/his.

I was genuinely unaware of this. Just so I get this right:
- Add just the 'Sob:' for patches from others that I post un-modified 
  (without a Co-developed-by: tag)
- Add 'Co-developed-by:' if I make any changes to the patch (commit log 
  included?)


Thanks,
Naveen