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Re: [Qemu-devel] [Qemu-ppc] [PATCH] pseries: Implements h_read hcall


From: David Gibson
Subject: Re: [Qemu-devel] [Qemu-ppc] [PATCH] pseries: Implements h_read hcall
Date: Wed, 13 Feb 2013 16:21:49 +1100
User-agent: Mutt/1.5.21 (2010-09-15)

On Tue, Feb 12, 2013 at 11:07:10PM +0100, Alexander Graf wrote:
> 
> On 07.02.2013, at 12:28, Erlon Cruz wrote:
> 
> > From: Erlon Cruz <address@hidden>
> > 
> > This h_call is useful for DLPAR in future amongst other things. Given an 
> > index
> > it fetches the corresponding PTE stored in the htab.
> > 
> > Signed-off-by: Erlon Cruz <address@hidden>
> > ---
> > hw/spapr_hcall.c |   58 
> > ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 58 insertions(+)
> > 
> > diff --git a/hw/spapr_hcall.c b/hw/spapr_hcall.c
> > index 2889742..5ba07e5 100644
> > --- a/hw/spapr_hcall.c
> > +++ b/hw/spapr_hcall.c
> > @@ -323,6 +323,63 @@ static target_ulong h_protect(PowerPCCPU *cpu, 
> > sPAPREnvironment *spapr,
> >     return H_SUCCESS;
> > }
> > 
> > +static target_ulong h_read(PowerPCCPU *cpu, sPAPREnvironment *spapr,
> > +                            target_ulong opcode, target_ulong *args)
> > +{
> > +    CPUPPCState *env = &cpu->env;
> > +    target_ulong flags = args[0];
> > +    target_ulong pte_index = args[1];
> > +    uint8_t *hpte;
> > +
> > +    if ((pte_index * HASH_PTE_SIZE_64) & ~env->htab_mask) {
> > +        return H_PARAMETER;
> > +    }
> > +
> > +    if (!(flags & H_READ_4)) {
> > +        target_ulong v, r;
> > +        target_ulong *pteh = &args[0];
> > +        target_ulong *ptel = &args[1];
> > +
> > +        hpte = env->external_htab + (pte_index * HASH_PTE_SIZE_64);
> 
> You are not guaranteed that there is an external htab.

Actually in the case of spapr, you are - the existing hash table
management calls all assume the existence of an external htab.

> In fact, looking at the external_htab users, we should probably
> introduce a few helper read functions for the htab that abstract the
> glorious external_htab/htab_base details away from you.

That said, I actually wrote such helpers about 15 minutes ago as part
of my MMU cleanup series.

-- 
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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