Re: [PATCH v4 5/7] KVM: PPC: clean up redundant kvm_run parameters in assembly

[Tianjia Zhang]

On 2020/5/26 13:59, Paul Mackerras wrote:
> On Mon, Apr 27, 2020 at 12:35:12PM +0800, Tianjia Zhang wrote:
> > In the current kvm version, 'kvm_run' has been included in the 'kvm_vcpu'
> > structure. For historical reasons, many kvm-related function parameters
> > retain the 'kvm_run' and 'kvm_vcpu' parameters at the same time. This
> > patch does a unified cleanup of these remaining redundant parameters.
>
> Some of these changes don't look completely correct to me, see below.
> If you're expecting these patches to go through my tree, I can fix up
> the patch and commit it (with you as author), noting the changes I
> made in the commit message.  Do you want me to do that?

I am very glad for you to do so, although I have submitted a new version 
of patch, I still prefer you to fix up and commit it.

Thanks and best,
Tianjia

> > diff --git a/arch/powerpc/kvm/book3s_interrupts.S b/arch/powerpc/kvm/book3s_interrupts.S
> > index f7ad99d972ce..0eff749d8027 100644
> > --- a/arch/powerpc/kvm/book3s_interrupts.S
> > +++ b/arch/powerpc/kvm/book3s_interrupts.S
> > @@ -55,8 +55,7 @@
> >    ****************************************************************************/
> >   
> >   /* Registers:
> > - *  r3: kvm_run pointer
> > - *  r4: vcpu pointer
> > + *  r3: vcpu pointer
> >    */
> >   _GLOBAL(__kvmppc_vcpu_run)
> >   
> > @@ -68,8 +67,8 @@ kvm_start_entry:
> >   	/* Save host state to the stack */
> >   	PPC_STLU r1, -SWITCH_FRAME_SIZE(r1)
> >   
> > -	/* Save r3 (kvm_run) and r4 (vcpu) */
> > -	SAVE_2GPRS(3, r1)
> > +	/* Save r3 (vcpu) */
> > +	SAVE_GPR(3, r1)
> >   
> >   	/* Save non-volatile registers (r14 - r31) */
> >   	SAVE_NVGPRS(r1)
> > @@ -82,11 +81,11 @@ kvm_start_entry:
> >   	PPC_STL	r0, _LINK(r1)
> >   
> >   	/* Load non-volatile guest state from the vcpu */
> > -	VCPU_LOAD_NVGPRS(r4)
> > +	VCPU_LOAD_NVGPRS(r3)
> >   
> >   kvm_start_lightweight:
> >   	/* Copy registers into shadow vcpu so we can access them in real mode */
> > -	mr	r3, r4
> > +	mr	r4, r3
>
> This mr doesn't seem necessary.
>
> >   	bl	FUNC(kvmppc_copy_to_svcpu)
> >   	nop
> >   	REST_GPR(4, r1)
>
> This should be loading r4 from GPR3(r1), not GPR4(r1) - which is what
> REST_GPR(4, r1) will do.
>
> Then, in the file but not in the patch context, there is this line:
>
> 	PPC_LL	r3, GPR4(r1)		/* vcpu pointer */
>
> where once again GPR4 needs to be GPR3.
>
> > @@ -191,10 +190,10 @@ after_sprg3_load:
> >   	PPC_STL	r31, VCPU_GPR(R31)(r7)
> >   
> >   	/* Pass the exit number as 3rd argument to kvmppc_handle_exit */
>
> The comment should be modified to say "2nd" instead of "3rd",
> otherwise it is confusing.
>
> The rest of the patch looks OK.
>
> Paul.