Re: [PATCH v2] KVM: x86: Fix poll command

[Sean Christopherson]

On Thu, Apr 13, 2023, alexjlzheng@xxxxxxxxx wrote:
> From: Jinliang Zheng <alexjlzheng@xxxxxxxxxxx>
> 
> According to the hardware manual, when the Poll command is issued, the

Please add "8259", i.e. "According to the 8259 hardware manual".

> byte returned by the I/O read is 1 in Bit 7 when there is an interrupt,
> and the highest priority binary code in Bits 2:0. The current pic
> simulation code is not implemented strictly according to the above
> expression.
> 
> Fix the implementation of pic_poll_read():
> 1. Set Bit 7 when there is an interrupt
> 2. Return 0 when there is no interrupt

I don't think #2 is justified.  The spec says:

  The interrupt requests are ordered in priority from 0 through 7 (0 highest).

I.e. the current code enumerates the _lowest_ priority when there is no interrupt,
which seems more correct than reporting the highest priority possible.