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

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Message-ID: <76047748-9ddd-5ba3-fe4d-85c7c08bd521@ozlabs.ru>
Date:   Wed, 1 Jul 2020 18:04:41 +1000
From:   Alexey Kardashevskiy <aik@...abs.ru>
To:     Leonardo Bras <leobras.c@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        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 27/06/2020 03:46, Leonardo Bras wrote:
> 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.

I'd rather suggest this:

https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20180725095032.2196-2-aik@ozlabs.ru/

Although it does not look like you are actually going to have windows
starting at 0. Thanks,

> Please keep reviewing patches 1-5.
> 
> Best regards,
> Leonardo
> 

-- 
Alexey