Re: [PATCH v4] KVM: VMX: Improve handle_external_interrupt_irqoff inline assembly

Sean Christopherson
2020-05-04T15:33:45Z

On Mon, May 04, 2020 at 05:32:19PM +0200, Uros Bizjak wrote:
> On Mon, May 4, 2020 at 5:25 PM Sean Christopherson
> <sean.j.christopherson@intel.com> wrote:
> >
> > On Mon, May 04, 2020 at 01:05:45AM +0200, Uros Bizjak wrote:
> > > Improve handle_external_interrupt_irqoff inline assembly in several ways:
> > > - use "re" operand constraint instead of "i" and remove
> > > unneeded %c operand modifiers and "$" prefixes
> > > - use %rsp instead of _ASM_SP, since we are in CONFIG_X86_64 part
> > > - use $-16 immediate to align %rsp
> > > - remove unneeded use of __ASM_SIZE macro
> > > - define "ss" named operand only for X86_64
> > >
> > > The patch introduces no functional changes.
> >
> > Hmm, for handcoded assembly I would argue that the switch from "i" to "re"
> > is a functional change of sorts. The switch also needs explicit
> > justification to explain why it's correct/desirable. Maybe make it a
> > separate patch?
>
> I think this would be a good idea. So, in this patch the first point should read
>
> "- remove unneeded %c operand modifiers and "$" prefixes"
>
> The add-on patch will then explain that PUSH can only handle signed
> 32bit immediates and change "i" to "re".
>
> Is this what you had in mind?

Yep, exactly.