Re: [PATCH v3 11/12] target/ppc: Streamline construction of VRMA SLB entry

[David Gibson]

On Wed, Feb 19, 2020 at 11:34:22AM -0300, Fabiano Rosas wrote:
> David Gibson <address@hidden> writes:
> 
> 
> Hi, just a nitpick, feel free to ignore.
> 
> > When in VRMA mode (i.e. a guest thinks it has the MMU off, but the
> > hypervisor is still applying translation) we use a special SLB entry,
> > rather than looking up an SLBE by address as we do when guest translation
> > is on.
> >
> > We build that special entry in ppc_hash64_update_vrma() along with some
> > logic for handling some non-VRMA cases.  Split the actual build of the
> > VRMA SLBE into a separate helper and streamline it a bit.
> >
> > Signed-off-by: David Gibson <address@hidden>
> > ---
> >  target/ppc/mmu-hash64.c | 79 ++++++++++++++++++++---------------------
> >  1 file changed, 38 insertions(+), 41 deletions(-)
> >
> > diff --git a/target/ppc/mmu-hash64.c b/target/ppc/mmu-hash64.c
> > index 170a78bd2e..06cfff9860 100644
> > --- a/target/ppc/mmu-hash64.c
> > +++ b/target/ppc/mmu-hash64.c
> > @@ -789,6 +789,39 @@ static target_ulong rmls_limit(PowerPCCPU *cpu)
> >      }
> >  }
> >  
> > +static int build_vrma_slbe(PowerPCCPU *cpu, ppc_slb_t *slb)
> > +{
> > +    CPUPPCState *env = &cpu->env;
> > +    target_ulong lpcr = env->spr[SPR_LPCR];
> > +    uint32_t vrmasd = (lpcr & LPCR_VRMASD) >> LPCR_VRMASD_SHIFT;
> > +    target_ulong vsid = SLB_VSID_VRMA | ((vrmasd << 4) & 
> > SLB_VSID_LLP_MASK);
> > +    int i;
> > +
> > +    /*
> > +     * Make one up. Mostly ignore the ESID which will not be needed
> > +     * for translation
> > +     */
> 
> I find this comment a bit vague. I suggest we either leave it behind or
> make it more precise. The ISA says:
> 
> "translation of effective addresses to virtual addresses use the SLBE
> values in Figure 18 instead of the entry in the SLB corresponding to the
> ESID"

Yeah, it wasn't very helpful in its initial location, and it's even
less helpful here.  I've dropped it.

-- 
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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