Subject: Re: [PATCH v4 04/29] KVM: PPC: Book3S PR: Move kvmppc_save_tm/kvmppc_restore_tm to separate file

From: Simon Guo <[email-masked]>
Date: Wed, 30 May 2018 17:04:49 +0800

On Wed, May 30, 2018 at 09:40:27AM +1000, Paul Mackerras wrote:
> On Wed, May 23, 2018 at 03:01:47PM +0800, [email-masked] wrote:
> > From: Simon Guo <[email-masked]>
> > 
> > It is a simple patch just for moving kvmppc_save_tm/kvmppc_restore_tm()
> > functionalities to tm.S. There is no logic change. The reconstruct of
> > those APIs will be done in later patches to improve readability.
> > 
> > It is for preparation of reusing those APIs on both HV/PR PPC KVM.
> > 
> > Some slight change during move the functions includes:
> > - surrounds some HV KVM specific code with CONFIG_KVM_BOOK3S_HV_POSSIBLE
> > for compilation.
> > - use _GLOBAL() to define kvmppc_save_tm/kvmppc_restore_tm()
> > 
> > Signed-off-by: Simon Guo <[email-masked]>
> > ---
> >  arch/powerpc/kvm/Makefile               |   3 +
> >  arch/powerpc/kvm/book3s_hv_rmhandlers.S | 322 ----------------------------
> >  arch/powerpc/kvm/tm.S                   | 363 ++++++++++++++++++++++++++++++++
> >  3 files changed, 366 insertions(+), 322 deletions(-)
> >  create mode 100644 arch/powerpc/kvm/tm.S
> > 
> > diff --git a/arch/powerpc/kvm/Makefile b/arch/powerpc/kvm/Makefile
> > index 4b19da8..f872c04 100644
> > --- a/arch/powerpc/kvm/Makefile
> > +++ b/arch/powerpc/kvm/Makefile
> > @@ -63,6 +63,9 @@ kvm-pr-y := \
> >  	book3s_64_mmu.o \
> >  	book3s_32_mmu.o
> >  
> > +kvm-book3s_64-builtin-objs-$(CONFIG_KVM_BOOK3S_64_HANDLER) += \
> > +	tm.o
> > +
> >  ifdef CONFIG_KVM_BOOK3S_PR_POSSIBLE
> >  kvm-book3s_64-builtin-objs-$(CONFIG_KVM_BOOK3S_64_HANDLER) += \
> >  	book3s_rmhandlers.o
> > diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> > index 5e6e493..4db2b10 100644
> > --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> > +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> > @@ -39,8 +39,6 @@ BEGIN_FTR_SECTION;				\
> >  	extsw	reg, reg;			\
> >  END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300)
> >  
> > -#define VCPU_GPRS_TM(reg) (((reg) * ULONG_SIZE) + VCPU_GPR_TM)
> > -
> >  /* Values in HSTATE_NAPPING(r13) */
> >  #define NAPPING_CEDE	1
> >  #define NAPPING_NOVCPU	2
> > @@ -3119,326 +3117,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
> >  	mr	r4,r31
> >  	blr
> >  
> > -#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
> > -/*
> > - * Save transactional state and TM-related registers.
> > - * Called with r9 pointing to the vcpu struct.
> > - * This can modify all checkpointed registers, but
> > - * restores r1, r2 and r9 (vcpu pointer) before exit.
> > - */
> > -kvmppc_save_tm:
> > -	mflr	r0
> > -	std	r0, PPC_LR_STKOFF(r1)
> > -	stdu	r1, -PPC_MIN_STKFRM(r1)
> > -
> > -	/* Turn on TM. */
> > -	mfmsr	r8
> > -	li	r0, 1
> > -	rldimi	r8, r0, MSR_TM_LG, 63-MSR_TM_LG
> > -	mtmsrd	r8
> > -
> > -	ld	r5, VCPU_MSR(r9)
> > -	rldicl. r5, r5, 64 - MSR_TS_S_LG, 62
> > -	beq	1f	/* TM not active in guest. */
> > -
> > -	std	r1, HSTATE_HOST_R1(r13)
> > -	li	r3, TM_CAUSE_KVM_RESCHED
> > -
> > -BEGIN_FTR_SECTION
> > -	lbz	r0, HSTATE_FAKE_SUSPEND(r13) /* Were we fake suspended? */
> > -	cmpwi	r0, 0
> > -	beq	3f
> > -	rldicl. r8, r8, 64 - MSR_TS_S_LG, 62 /* Did we actually hrfid? */
> > -	beq	4f
> > -BEGIN_FTR_SECTION_NESTED(96)
> > -	bl	pnv_power9_force_smt4_catch
> > -END_FTR_SECTION_NESTED(CPU_FTR_P9_TM_XER_SO_BUG, CPU_FTR_P9_TM_XER_SO_BUG, 96)
> > -	nop
> > -	b	6f
> > -3:
> > -	/* Emulation of the treclaim instruction needs TEXASR before treclaim */
> > -	mfspr	r6, SPRN_TEXASR
> > -	std	r6, VCPU_ORIG_TEXASR(r9)
> > -6:
> > -END_FTR_SECTION_IFSET(CPU_FTR_P9_TM_HV_ASSIST)
> 
> It worries me that we now have this TM hypervisor assist stuff in a
> place where it could be active with PR KVM.  I think it would be
> better to factor out the TM assist code into a separate function which
> then calls kvmppc_save_tm if it needs to do an actual treclaim.  I'll
> look at doing that.
Paul,
Thanks for the info. Please let me know if anything I can help.

BR,
- Simon