linux-kernel - Re: [PATCH v2 1/1] powerpc/iommu: Enable remaining IOMMU Pagesizes present in LoPAR

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Date:   Thu, 08 Apr 2021 03:35:41 -0300
From:   Leonardo Bras <leobras.c@...il.com>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Alexey Kardashevskiy <aik@...abs.ru>, brking@...ux.vnet.ibm.com
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] powerpc/iommu: Enable remaining IOMMU Pagesizes
 present in LoPAR

On Thu, 2021-04-08 at 03:20 -0300, Leonardo Bras wrote:
> > > +#define QUERY_DDW_PGSIZE_4K	0x01
> > > +#define QUERY_DDW_PGSIZE_64K	0x02
> > > +#define QUERY_DDW_PGSIZE_16M	0x04
> > > +#define QUERY_DDW_PGSIZE_32M	0x08
> > > +#define QUERY_DDW_PGSIZE_64M	0x10
> > > +#define QUERY_DDW_PGSIZE_128M	0x20
> > > +#define QUERY_DDW_PGSIZE_256M	0x40
> > > +#define QUERY_DDW_PGSIZE_16G	0x80
> > 
> > I'm not sure the #defines really gain us much vs just putting the
> > literal values in the array below?
> 
> My v1 did not use the define approach, what do you think of that?
> http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20210322190943.715368-1-leobras.c@gmail.com/
> 
> 
(of course, it would be that without the pageshift defines also, using
the __builtin_ctz() approach suggested by Alexey.)