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Re: [PATCH v3 04/12] target/ppc: Introduce ppc_hash64_use_vrma() helper


From: David Gibson
Subject: Re: [PATCH v3 04/12] target/ppc: Introduce ppc_hash64_use_vrma() helper
Date: Thu, 20 Feb 2020 14:10:48 +1100

On Wed, Feb 19, 2020 at 11:06:20AM -0300, Fabiano Rosas wrote:
> David Gibson <address@hidden> writes:
> 
> > When running guests under a hypervisor, the hypervisor obviously needs to
> > be protected from guest accesses even if those are in what the guest
> > considers real mode (translation off).  The POWER hardware provides two
> > ways of doing that: The old way has guest real mode accesses simply offset
> > and bounds checked into host addresses.  It works, but requires that a
> > significant chunk of the guest's memory - the RMA - be physically
> > contiguous in the host, which is pretty inconvenient.  The new way, known
> > as VRMA, has guest real mode accesses translated in roughly the normal way
> > but with some special parameters.
> >
> > In POWER7 and POWER8 the LPCR[VPM0] bit selected between the two modes, but
> > in POWER9 only VRMA mode is supported
> 
> ... when translation is off, right? Because I see in the 3.0 ISA that
> LPCR[VPM1] is still there.

Right.  This whole patch (and the whole series) is about when the
guest is in translation off mode.

> 
> > and LPCR[VPM0] no longer exists.  We
> > handle that difference in behaviour in ppc_hash64_set_isi().. but not in
> > other places that we blindly check LPCR[VPM0].
> >
> > Correct those instances with a new helper to tell if we should be in VRMA
> > mode.
> >
> > Signed-off-by: David Gibson <address@hidden>
> > Reviewed-by: C├ędric Le Goater <address@hidden>
> > ---
> >  target/ppc/mmu-hash64.c | 41 +++++++++++++++++++----------------------
> >  1 file changed, 19 insertions(+), 22 deletions(-)
> >
> > diff --git a/target/ppc/mmu-hash64.c b/target/ppc/mmu-hash64.c
> > index 5fabd93c92..d878180df5 100644
> > --- a/target/ppc/mmu-hash64.c
> > +++ b/target/ppc/mmu-hash64.c
> > @@ -668,6 +668,19 @@ unsigned ppc_hash64_hpte_page_shift_noslb(PowerPCCPU 
> > *cpu,
> >      return 0;
> >  }
> >  
> > +static bool ppc_hash64_use_vrma(CPUPPCState *env)
> > +{
> > +    switch (env->mmu_model) {
> > +    case POWERPC_MMU_3_00:
> > +        /* ISAv3.0 (POWER9) always uses VRMA, the VPM0 field and RMOR
> > +         * register no longer exist */
> > +        return true;
> > +
> > +    default:
> > +        return !!(env->spr[SPR_LPCR] & LPCR_VPM0);
> > +    }
> > +}
> > +
> >  static void ppc_hash64_set_isi(CPUState *cs, uint64_t error_code)
> >  {
> >      CPUPPCState *env = &POWERPC_CPU(cs)->env;
> > @@ -676,15 +689,7 @@ static void ppc_hash64_set_isi(CPUState *cs, uint64_t 
> > error_code)
> >      if (msr_ir) {
> >          vpm = !!(env->spr[SPR_LPCR] & LPCR_VPM1);
> >      } else {
> > -        switch (env->mmu_model) {
> > -        case POWERPC_MMU_3_00:
> > -            /* Field deprecated in ISAv3.00 - interrupts always go to 
> > hyperv */
> > -            vpm = true;
> > -            break;
> > -        default:
> > -            vpm = !!(env->spr[SPR_LPCR] & LPCR_VPM0);
> > -            break;
> > -        }
> > +        vpm = ppc_hash64_use_vrma(env);
> >      }
> >      if (vpm && !msr_hv) {
> >          cs->exception_index = POWERPC_EXCP_HISI;
> > @@ -702,15 +707,7 @@ static void ppc_hash64_set_dsi(CPUState *cs, uint64_t 
> > dar, uint64_t dsisr)
> >      if (msr_dr) {
> >          vpm = !!(env->spr[SPR_LPCR] & LPCR_VPM1);
> >      } else {
> > -        switch (env->mmu_model) {
> > -        case POWERPC_MMU_3_00:
> > -            /* Field deprecated in ISAv3.00 - interrupts always go to 
> > hyperv */
> > -            vpm = true;
> > -            break;
> > -        default:
> > -            vpm = !!(env->spr[SPR_LPCR] & LPCR_VPM0);
> > -            break;
> > -        }
> > +        vpm = ppc_hash64_use_vrma(env);
> >      }
> >      if (vpm && !msr_hv) {
> >          cs->exception_index = POWERPC_EXCP_HDSI;
> > @@ -799,7 +796,7 @@ int ppc_hash64_handle_mmu_fault(PowerPCCPU *cpu, vaddr 
> > eaddr,
> >              if (!(eaddr >> 63)) {
> >                  raddr |= env->spr[SPR_HRMOR];
> >              }
> > -        } else if (env->spr[SPR_LPCR] & LPCR_VPM0) {
> > +        } else if (ppc_hash64_use_vrma(env)) {
> >              /* Emulated VRMA mode */
> >              slb = &env->vrma_slb;
> >              if (!slb->sps) {
> > @@ -967,7 +964,7 @@ hwaddr ppc_hash64_get_phys_page_debug(PowerPCCPU *cpu, 
> > target_ulong addr)
> >          } else if ((msr_hv || !env->has_hv_mode) && !(addr >> 63)) {
> >              /* In HV mode, add HRMOR if top EA bit is clear */
> >              return raddr | env->spr[SPR_HRMOR];
> > -        } else if (env->spr[SPR_LPCR] & LPCR_VPM0) {
> > +        } else if (ppc_hash64_use_vrma(env)) {
> >              /* Emulated VRMA mode */
> >              slb = &env->vrma_slb;
> >              if (!slb->sps) {
> > @@ -1056,8 +1053,7 @@ static void ppc_hash64_update_vrma(PowerPCCPU *cpu)
> >      slb->sps = NULL;
> >  
> >      /* Is VRMA enabled ? */
> > -    lpcr = env->spr[SPR_LPCR];
> > -    if (!(lpcr & LPCR_VPM0)) {
> > +    if (ppc_hash64_use_vrma(env)) {
> 
> Shouldn't this be !ppc_hash64_use_vrma(env)?
> 
> And a comment about the original code: all other places that check
> LPCR_VPM0 do it after verifying that translation is off, except here
> (ppc_hash64_update_vrma). Could that be an issue?
> 
> >          return;
> >      }
> >  
> > @@ -1065,6 +1061,7 @@ static void ppc_hash64_update_vrma(PowerPCCPU *cpu)
> >       * Make one up. Mostly ignore the ESID which will not be needed
> >       * for translation
> >       */
> > +    lpcr = env->spr[SPR_LPCR];
> >      vsid = SLB_VSID_VRMA;
> >      vrmasd = (lpcr & LPCR_VRMASD) >> LPCR_VRMASD_SHIFT;
> >      vsid |= (vrmasd << 4) & (SLB_VSID_L | SLB_VSID_LP);
> 

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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