linux-kernel - Re: [PATCH v2 6/6] powerpc/pseries/iommu: Avoid errors when DDW starts at 0x00

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Date:   Fri, 26 Jun 2020 14:46:46 -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>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        Ram Pai <linuxram@...ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 6/6] powerpc/pseries/iommu: Avoid errors when DDW
 starts at 0x00

On Wed, 2020-06-24 at 03:24 -0300, Leonardo Bras wrote:
> As of today, enable_ddw() will return a non-null DMA address if the
> created DDW maps the whole partition. If the address is valid,
> iommu_bypass_supported_pSeriesLP() will consider iommu bypass enabled.
> 
> This can cause some trouble if the DDW happens to start at 0x00.
> 
> Instead if checking if the address is non-null, check directly if
> the DDW maps the whole partition, so it can bypass iommu.
> 
> Signed-off-by: Leonardo Bras <leobras.c@...il.com>

This patch has a bug in it. I will rework it soon.
Please keep reviewing patches 1-5.

Best regards,
Leonardo