Re: [PATCH 2/2] KVM: x86: Adjust return value of pic_poll_read()

[Sean Christopherson]

On Tue, Apr 18, 2023, alexjlzheng@xxxxxxxxx wrote:
> From: Jinliang Zheng <alexjlzheng@xxxxxxxxxxx>
> 
> Returning 0x07 raises ambiguity when no interrupt is in pic_poll_read().
> Although it will not cause a functional exception (Bit 7 is 0 means no

>From KVM's perspective, it's a functional change.  It _shouldn't_ impact the
overall functionality of the guest, but we have no idea what guest code exists
in the wild.

> interrupt), it will easily make developers mistakenly think that a
> spurious interrupt (IRQ 7) has been returned.
> 
> Return 0x00 instread of 0x07.

Again, I do not want to introduce a functional change in this code without evidence
that the change fixes something for a real world guest.  Based on your response[*],
that is not the case.

A comment explaining the KVM behavior would be very welcome, but I'm not taking
this patch.

[*] https://lore.kernel.org/all/20230418075923.752113-1-alexjlzheng@xxxxxxxxxxx