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Message-ID: <ca699edfe2382bef01d1af26b5c7264571ef6adb.camel@gmail.com>
Subject: Re: [PATCH v2 6/6] powerpc/pseries/iommu: Avoid errors when DDW
 starts at 0x00
From:   Leonardo Bras <leobras.c@gmail.com>
To:     Alexey Kardashevskiy <aik@ozlabs.ru>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Thiago Jung Bauermann <bauerman@linux.ibm.com>,
        Ram Pai <linuxram@us.ibm.com>
Cc:     linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Date:   Wed, 01 Jul 2020 16:59:37 -0300
In-Reply-To: <76047748-9ddd-5ba3-fe4d-85c7c08bd521@ozlabs.ru>
References: <20200624062411.367796-1-leobras.c@gmail.com>
         <20200624062411.367796-7-leobras.c@gmail.com>
         <1069466fa3a373e92d9db18957674b1d9c6e9cf2.camel@gmail.com>
         <76047748-9ddd-5ba3-fe4d-85c7c08bd521@ozlabs.ru>
Organization: IBM
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On Wed, 2020-07-01 at 18:04 +1000, Alexey Kardashevskiy wrote:
> 
> 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@gmail.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,

Yeah, agree. 
I am thinking of dropping this one, as I don't see much good to be done
here.

Thank you!