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Message-ID: <4edd762ee53060db6ae3d58aa45ea25887c04a47.camel@gmail.com>
Subject: Re: [PATCH v5 0/4] Allow bigger 64bit window by removing default
 DMA window
From:   Leonardo Bras <leobras.c@gmail.com>
To:     Michael Ellerman <mpe@ellerman.id.au>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Alexey Kardashevskiy <aik@ozlabs.ru>,
        Thiago Jung Bauermann <bauerman@linux.ibm.com>,
        Ram Pai <linuxram@us.ibm.com>,
        Brian King <brking@linux.vnet.ibm.com>,
        Murilo Fossa Vicentini <muvic@linux.ibm.com>,
        David Dai <zdai@linux.vnet.ibm.com>
Cc:     linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Date:   Wed, 12 Aug 2020 01:42:56 -0300
In-Reply-To: <20200805030455.123024-1-leobras.c@gmail.com>
References: <20200805030455.123024-1-leobras.c@gmail.com>
Organization: IBM
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Hello Michael,

Do you suggest any change for this patchset?
Any chance it can get in this merge window?

Best regards,
Leonardo Bras

On Wed, 2020-08-05 at 00:04 -0300, Leonardo Bras wrote:
> There are some devices in which a hypervisor may only allow 1 DMA window
> to exist at a time, and in those cases, a DDW is never created to them,
> since the default DMA window keeps using this resource.
> 
> LoPAR recommends this procedure:
> 1. Remove the default DMA window,
> 2. Query for which configs the DDW can be created,
> 3. Create a DDW.
> 
> Patch #1:
> Create defines for outputs of ibm,ddw-applicable, so it's easier to
> identify them.
> 
> Patch #2:
> - After LoPAR level 2.8, there is an extension that can make
>   ibm,query-pe-dma-windows to have 6 outputs instead of 5. This changes the
>   order of the outputs, and that can cause some trouble. 
> - query_ddw() was updated to check how many outputs the 
>   ibm,query-pe-dma-windows is supposed to have, update the rtas_call() and
>   deal correctly with the outputs in both cases.
> - This patch looks somehow unrelated to the series, but it can avoid future
>   problems on DDW creation.
> 
> Patch #3 moves the window-removing code from remove_ddw() to
> remove_dma_window(), creating a way to delete any DMA window, so it can be
> used to delete the default DMA window.
> 
> Patch #4 makes use of the remove_dma_window() from patch #3 to remove the
> default DMA window before query_ddw(). It also implements a new rtas call
> to recover the default DMA window, in case anything fails after it was
> removed, and a DDW couldn't be created.
> 
> ---
> Changes since v4:
> - Removed patches 5+ in order to deal with a feature at a time
> - Remove unnecessary parentesis in patch #4
> - Changed patch #4 title from 
>   "Remove default DMA window before creating DDW"
> - Included David Dai tested-by
> - v4 link: http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=190051&state=%2A&archive=both
> 
> Changes since v3:
> - Introduces new patch #5, to prepare for an important change in #6
> - struct iommu_table was not being updated, so include a way to do this
>   in patch #6.
> - Improved patch #4 based in a suggestion from Alexey, to make code
>   more easily understandable
> - v3 link: http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=187348&state=%2A&archive=both
> 
> Changes since v2:
> - Change the way ibm,ddw-extensions is accessed, using a proper function
>   instead of doing this inline everytime it's used.
> - Remove previous patch #6, as it doesn't look like it would be useful.
> - Add new patch, for changing names from direct* to dma*, as indirect 
>   mapping can be used from now on.
> - Fix some typos, corrects some define usage.
> - v2 link: http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=185433&state=%2A&archive=both
> 
> Changes since v1:
> - Add defines for ibm,ddw-applicable and ibm,ddw-extensions outputs
> - Merge aux function query_ddw_out_sz() into query_ddw()
> - Merge reset_dma_window() patch (prev. #2) into remove default DMA
>   window patch (#4).
> - Keep device_node *np name instead of using pdn in remove_*()
> - Rename 'device_node *pdn' into 'parent' in new functions
> - Rename dfl_win to default_win
> - Only remove the default DMA window if there is no window available
>   in first query.
> - Check if default DMA window can be restored before removing it.
> - Fix 'unitialized use' (found by travis mpe:ci-test)
> - New patches #5 and #6
> - v1 link: http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=184420&state=%2A&archive=both
> 
> Special thanks for Alexey Kardashevskiy, Brian King and
> Oliver O'Halloran for the feedback provided!
> 
> 
> Leonardo Bras (4):
>   powerpc/pseries/iommu: Create defines for operations in
>     ibm,ddw-applicable
>   powerpc/pseries/iommu: Update call to ibm,query-pe-dma-windows
>   powerpc/pseries/iommu: Move window-removing part of remove_ddw into
>     remove_dma_window
>   powerpc/pseries/iommu: Allow bigger 64bit window by removing default
>     DMA window
> 
>  arch/powerpc/platforms/pseries/iommu.c | 242 ++++++++++++++++++++-----
>  1 file changed, 195 insertions(+), 47 deletions(-)
>