Re: [PATCH v4 6/8] KVM: PPC: Ultravisor: Restrict LDBAR access

[maddy <maddy@xxxxxxxxxxxxxxxxxx>]

On 01/07/19 11:24 AM, Alexey Kardashevskiy wrote:
> On 29/06/2019 06:08, Claudio Carvalho wrote:
> > When the ultravisor firmware is available, it takes control over the
> > LDBAR register. In this case, thread-imc updates and save/restore
> > operations on the LDBAR register are handled by ultravisor.
> What does LDBAR do? "Power ISA™ Version 3.0 B" or "User’s Manual POWER9
> Processor" do not tell.
LDBAR is a per-thread SPR used by thread-imc pmu to dump the counter 
data into memory.
LDBAR contains memory address along with few other configuration bits 
(it is populated
by the thread-imc pmu driver). It is populated and enabled only when any 
of the thread
imc pmu events are monitored.

Maddy
> > Signed-off-by: Claudio Carvalho <cclaudio@xxxxxxxxxxxxx>
> > Reviewed-by: Ram Pai <linuxram@xxxxxxxxxx>
> > Reviewed-by: Ryan Grimm <grimm@xxxxxxxxxxxxx>
> > Acked-by: Madhavan Srinivasan <maddy@xxxxxxxxxxxxxxxxxx>
> > Acked-by: Paul Mackerras <paulus@xxxxxxxxxx>
> > ---
> >   arch/powerpc/kvm/book3s_hv_rmhandlers.S   | 2 ++
> >   arch/powerpc/platforms/powernv/idle.c     | 6 ++++--
> >   arch/powerpc/platforms/powernv/opal-imc.c | 4 ++++
> >   3 files changed, 10 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> > index f9b2620fbecd..cffb365d9d02 100644
> > --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> > +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> > @@ -375,8 +375,10 @@ BEGIN_FTR_SECTION
> >   	mtspr	SPRN_RPR, r0
> >   	ld	r0, KVM_SPLIT_PMMAR(r6)
> >   	mtspr	SPRN_PMMAR, r0
> > +BEGIN_FW_FTR_SECTION_NESTED(70)
> >   	ld	r0, KVM_SPLIT_LDBAR(r6)
> >   	mtspr	SPRN_LDBAR, r0
> > +END_FW_FTR_SECTION_NESTED(FW_FEATURE_ULTRAVISOR, 0, 70)
> >   	isync
> >   FTR_SECTION_ELSE
> >   	/* On P9 we use the split_info for coordinating LPCR changes */
> > diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
> > index 77f2e0a4ee37..5593a2d55959 100644
> > --- a/arch/powerpc/platforms/powernv/idle.c
> > +++ b/arch/powerpc/platforms/powernv/idle.c
> > @@ -679,7 +679,8 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
> >   		sprs.ptcr	= mfspr(SPRN_PTCR);
> >   		sprs.rpr	= mfspr(SPRN_RPR);
> >   		sprs.tscr	= mfspr(SPRN_TSCR);
> > -		sprs.ldbar	= mfspr(SPRN_LDBAR);
> > +		if (!firmware_has_feature(FW_FEATURE_ULTRAVISOR))
> > +			sprs.ldbar	= mfspr(SPRN_LDBAR);
> >   
> >   		sprs_saved = true;
> >   
> > @@ -762,7 +763,8 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
> >   	mtspr(SPRN_PTCR,	sprs.ptcr);
> >   	mtspr(SPRN_RPR,		sprs.rpr);
> >   	mtspr(SPRN_TSCR,	sprs.tscr);
> > -	mtspr(SPRN_LDBAR,	sprs.ldbar);
> > +	if (!firmware_has_feature(FW_FEATURE_ULTRAVISOR))
> > +		mtspr(SPRN_LDBAR,	sprs.ldbar);
> >   
> >   	if (pls >= pnv_first_tb_loss_level) {
> >   		/* TB loss */
> > diff --git a/arch/powerpc/platforms/powernv/opal-imc.c b/arch/powerpc/platforms/powernv/opal-imc.c
> > index 1b6932890a73..5fe2d4526cbc 100644
> > --- a/arch/powerpc/platforms/powernv/opal-imc.c
> > +++ b/arch/powerpc/platforms/powernv/opal-imc.c
> > @@ -254,6 +254,10 @@ static int opal_imc_counters_probe(struct platform_device *pdev)
> >   	bool core_imc_reg = false, thread_imc_reg = false;
> >   	u32 type;
> >   
> > +	/* Disable IMC devices, when Ultravisor is enabled. */
> > +	if (firmware_has_feature(FW_FEATURE_ULTRAVISOR))
> > +		return -EACCES;
> > +
> >   	/*
> >   	 * Check whether this is kdump kernel. If yes, force the engines to
> >   	 * stop and return.