Re: [PATCH v5 1/3] powerpc/book3s64/radix: Add H_RPT_INVALIDATE pgsize encodings to mmu_psize_def

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Mar 02, 2021 at 09:51:28AM +0530, Bharata B Rao wrote:
> On Tue, Mar 02, 2021 at 12:28:34PM +1100, David Gibson wrote:
> > On Wed, Feb 24, 2021 at 01:55:08PM +0530, Bharata B Rao wrote:
> > > Add a field to mmu_psize_def to store the page size encodings
> > > of H_RPT_INVALIDATE hcall. Initialize this while scanning the radix
> > > AP encodings. This will be used when invalidating with required
> > > page size encoding in the hcall.
> > > 
> > > Signed-off-by: Bharata B Rao <bharata@linux.ibm.com>
> > > ---
> > >  arch/powerpc/include/asm/book3s/64/mmu.h | 1 +
> > >  arch/powerpc/mm/book3s64/radix_pgtable.c | 5 +++++
> > >  2 files changed, 6 insertions(+)
> > > 
> > > diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h b/arch/powerpc/include/asm/book3s/64/mmu.h
> > > index eace8c3f7b0a..c02f42d1031e 100644
> > > --- a/arch/powerpc/include/asm/book3s/64/mmu.h
> > > +++ b/arch/powerpc/include/asm/book3s/64/mmu.h
> > > @@ -19,6 +19,7 @@ struct mmu_psize_def {
> > >  	int		penc[MMU_PAGE_COUNT];	/* HPTE encoding */
> > >  	unsigned int	tlbiel;	/* tlbiel supported for that page size */
> > >  	unsigned long	avpnm;	/* bits to mask out in AVPN in the HPTE */
> > > +	unsigned long   h_rpt_pgsize; /* H_RPT_INVALIDATE page size encoding */
> > >  	union {
> > >  		unsigned long	sllp;	/* SLB L||LP (exact mask to use in slbmte) */
> > >  		unsigned long ap;	/* Ap encoding used by PowerISA 3.0 */
> > > diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c
> > > index 98f0b243c1ab..1b749899016b 100644
> > > --- a/arch/powerpc/mm/book3s64/radix_pgtable.c
> > > +++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
> > > @@ -486,6 +486,7 @@ static int __init radix_dt_scan_page_sizes(unsigned long node,
> > >  		def = &mmu_psize_defs[idx];
> > >  		def->shift = shift;
> > >  		def->ap  = ap;
> > > +		def->h_rpt_pgsize = psize_to_rpti_pgsize(idx);
> > >  	}
> > >  
> > >  	/* needed ? */
> > > @@ -560,9 +561,13 @@ void __init radix__early_init_devtree(void)
> > >  		 */
> > >  		mmu_psize_defs[MMU_PAGE_4K].shift = 12;
> > >  		mmu_psize_defs[MMU_PAGE_4K].ap = 0x0;
> > > +		mmu_psize_defs[MMU_PAGE_4K].h_rpt_pgsize =
> > > +			psize_to_rpti_pgsize(MMU_PAGE_4K);
> > 
> > Hm.  TBH, I was thinking of this as replacing psize_to_rpti_pgsize() -
> > that is, you directly put the correct codes in there, then just have
> > psize_to_rpti_pgsize() look them up in the table.
> > 
> > I guess that could be a followup change, though.
> > 
> > >  
> > >  		mmu_psize_defs[MMU_PAGE_64K].shift = 16;
> > >  		mmu_psize_defs[MMU_PAGE_64K].ap = 0x5;
> > > +		mmu_psize_defs[MMU_PAGE_64K].h_rpt_pgsize =
> > > +			psize_to_rpti_pgsize(MMU_PAGE_64K);
> 
> Hmm if you see I got rid of rpti_pgsize_to_psize() by having the
> defines directly in mmu_psize_def[].

I realize that, but I'm talking about the reverse direction:
psize_to_rpti_pgsize().  You should be able to reduce it a table
lookup, so the mmu_psize_defs table is the only place this information
exists.

> There are two cases in the above code (radix__early_init_devtree)
> 
> 1. If radix pagesize encodings are present in the DT, we walk
> the page sizes in the loop and populate the enconding for
> H_RPT_INVALIDATE. I am not sure if we can use the direct codes
> in this case.

I'm not understanding the problem.

In any case the existing implementation of psize

Why ever not?  You can just update the mmu_psize_defs when you parse
the device tree.  Plus AFAICT, the existing psize_to_rpti
implementation doesn't take into account any device tree eencodings.

> 2. If DT doesn't have the radix pagesize encodings, 4K and 64K
> sizes are assumed as fallback sizes where we can use direct
> encodings.

Right... still not seeing the problem.

-- 
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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