Re: [PATCH v3 14/16] powerpc/32: implement fast entry for syscalls on BOOKE

[Christophe Leroy]

Le 23/05/2019 Ã 08:14, Paul Mackerras a ÃcritÂ:
> On Tue, Apr 30, 2019 at 12:39:03PM +0000, Christophe Leroy wrote:
> > This patch implements a fast entry for syscalls.
> >
> > Syscalls don't have to preserve non volatile registers except LR.
> >
> > This patch then implement a fast entry for syscalls, where
> > volatile registers get clobbered.
> >
> > As this entry is dedicated to syscall it always sets MSR_EE
> > and warns in case MSR_EE was previously off
> >
> > It also assumes that the call is always from user, system calls are
> > unexpected from kernel.
>
> This is now upstream as commit 1a4b739bbb4f.  On the e500mc test
> config that I use, I'm getting this build failure:

Is that a standard defconfig ? If not, can you provide your .config ?

> arch/powerpc/kernel/head_fsl_booke.o: In function `SystemCall':
> arch/powerpc/kernel/head_fsl_booke.S:416: undefined reference to `kvmppc_handler_BOOKE_INTERRUPT_SYSCALL_SPRN_SRR1'
> Makefile:1052: recipe for target 'vmlinux' failed
>
> > +.macro SYSCALL_ENTRY trapno intno
> > +	mfspr	r10, SPRN_SPRG_THREAD
> > +#ifdef CONFIG_KVM_BOOKE_HV
> > +BEGIN_FTR_SECTION
> > +	mtspr	SPRN_SPRG_WSCRATCH0, r10
> > +	stw	r11, THREAD_NORMSAVE(0)(r10)
> > +	stw	r13, THREAD_NORMSAVE(2)(r10)
> > +	mfcr	r13			/* save CR in r13 for now	   */
> > +	mfspr	r11, SPRN_SRR1
> > +	mtocrf	0x80, r11	/* check MSR[GS] without clobbering reg */
> > +	bf	3, 1975f
> > +	b	kvmppc_handler_BOOKE_INTERRUPT_\intno\()_SPRN_SRR1
>
> It seems to me that the "_SPRN_SRR1" on the end of this line
> isn't meant to be there...  However, it still fails to link with that
> removed.

This SYSCALL_ENTRY macro is a slimmed version of NORMAL_EXCEPTION_PROLOG()

In NORMAL_EXCEPTION_PROLOG(), we have:
	DO_KVM	BOOKE_INTERRUPT_##intno SPRN_SRR1;	

The _SPRN_SRR1 comes from there


Then in /arch/powerpc/include/asm/kvm_booke_hv_asm.h:

.macro DO_KVM intno srr1
#ifdef CONFIG_KVM_BOOKE_HV
BEGIN_FTR_SECTION
	mtocrf	0x80, r11	/* check MSR[GS] without clobbering reg */
	bf	3, 1975f
	b	kvmppc_handler_\intno\()_\srr1
1975:
END_FTR_SECTION_IFSET(CPU_FTR_EMB_HV)
#endif
.endm


Christophe