linux-kernel - Re: [PATCH 4/4] powerpc/pseries/iommu: Remove default DMA window before creating DDW

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Message-ID: <03e82e1a1bcf516d01ca472546d8b31e468aba8b.camel@gmail.com>
Date:   Mon, 22 Jun 2020 23:43:24 -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>,
        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 4/4] powerpc/pseries/iommu: Remove default DMA window
 before creating DDW

On Tue, 2020-06-23 at 12:35 +1000, Alexey Kardashevskiy wrote:
> > I am not sure if this is true in general, but in this device (SR-IOV
> > VF) I am testing it will return 0 windows if the default DMA window is
> > not deleted, and 1 after it's deleted.
> 
> Since pHyp can only create windows in "64bit space", now (I did not know
> until a few month back) I expect that thing to return "1" always no
> matter what happened to the default window. And removing the default
> window will only affect the maximum number of TCEs but not the number of
> possible windows.

Humm, something gone wrong then.

This patchset was developed mostly because on testing, DDW would never
be created because windows_available would always be 0.

I will take a deeper look in that.

Best regards,
Leonardo