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

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Message-ID: <87blapdtyx.fsf@mpe.ellerman.id.au>
Date:   Thu, 08 Apr 2021 19:08:22 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Leonardo Bras <leobras.c@...il.com>,
        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

Leonardo Bras <leobras.c@...il.com> writes:
> 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.)

Yeah I think I like that better.

cheers