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

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Date:   Wed, 07 Apr 2021 16:58:27 -0300
From:   Leonardo Bras <leobras.c@...il.com>
To:     Alexey Kardashevskiy <aik@...abs.ru>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Christophe Leroy <christophe.leroy@....fr>,
        Joel Stanley <joel@....id.au>, brking@...ux.vnet.ibm.com
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] powerpc/iommu: Enable remaining IOMMU Pagesizes
 present in LoPAR

Hello Alexey,

On Tue, 2021-03-23 at 18:41 +1100, Alexey Kardashevskiy wrote:
[...]
> > +#define IOMMU_PAGE_SHIFT_16G	34
> > +#define IOMMU_PAGE_SHIFT_256M	28
> > +#define IOMMU_PAGE_SHIFT_128M	27
> > +#define IOMMU_PAGE_SHIFT_64M	26
> > +#define IOMMU_PAGE_SHIFT_32M	25
> > +#define IOMMU_PAGE_SHIFT_16M	24
> > +#define IOMMU_PAGE_SHIFT_64K	16
> 
> 
> These are not very descriptive, these are just normal shifts, could be 
> as simple as __builtin_ctz(SZ_4K) (gcc will optimize this) and so on.
> 
> OTOH the PAPR page sizes need macros as they are the ones which are 
> weird and screaming for macros.
> 
> I'd steal/rework spapr_page_mask_to_query_mask() from QEMU. Thanks,
> 

Thanks for this feedback!
I just sent a v2 applying your suggestions.

Best regards,
Leonardo Bras