linux-kernel - Re: [PATCH v5 08/11] powerpc/pseries/iommu: Update remove_dma

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Message-ID: <f9f7bcd75d534ebde7cc83c4138176da4680e30f.camel@gmail.com>
Date:   Tue, 17 Aug 2021 03:12:38 -0300
From:   Leonardo Brás <leobras.c@...il.com>
To:     Frederic Barrat <fbarrat@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        David Gibson <david@...son.dropbear.id.au>,
        kernel test robot <lkp@...el.com>,
        Nicolin Chen <nicoleotsuka@...il.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 08/11] powerpc/pseries/iommu: Update
 remove_dma_window() to accept property name

On Tue, 2021-08-17 at 02:59 -0300, Leonardo Brás wrote:
> Hello Fred, thanks for the feedback!
> 
> On Tue, 2021-07-20 at 19:51 +0200, Frederic Barrat wrote:
> > 
> > 
> > On 16/07/2021 10:27, Leonardo Bras wrote:
> > > Update remove_dma_window() so it can be used to remove DDW with a
> > > given
> > > property name.
> > > 
> > > This enables the creation of new property names for DDW, so we
> > > can
> > > have different usage for it, like indirect mapping.
> > > 
> > > Signed-off-by: Leonardo Bras <leobras.c@...il.com>
> > > Reviewed-by: Alexey Kardashevskiy <aik@...abs.ru>
> > > ---
> > >   arch/powerpc/platforms/pseries/iommu.c | 21 +++++++++++--------
> > > --
> > >   1 file changed, 11 insertions(+), 10 deletions(-)
> > > 
> > > diff --git a/arch/powerpc/platforms/pseries/iommu.c
> > > b/arch/powerpc/platforms/pseries/iommu.c
> > > index 108c3dcca686..17c6f4706e76 100644
> > > --- a/arch/powerpc/platforms/pseries/iommu.c
> > > +++ b/arch/powerpc/platforms/pseries/iommu.c
> > > @@ -830,31 +830,32 @@ static void remove_dma_window(struct
> > > device_node *np, u32 *ddw_avail,
> > >                         np, ret,
> > > ddw_avail[DDW_REMOVE_PE_DMA_WIN],
> > > liobn);
> > >   }
> > >   
> > > -static void remove_ddw(struct device_node *np, bool remove_prop)
> > > +static int remove_ddw(struct device_node *np, bool remove_prop,
> > > const char *win_name)
> > >   {
> > 
> > 
> > Why switch to returning an int? None of the callers check it.
> 
> IIRC, in a previous version it did make sense, which is not the case
> anymore. I will revert this.
> 
> Thanks!

Oh, sorry about that, it is in fact still needed:

It will make sense in patch v5 10/11:
On iommu_reconfig_notifier(), if (action == OF_RECONFIG_DETACH_NODE),
we need to remove a DDW if it exists.

As there may be different window names, it tests for DIRECT64_PROPNAME,
and if it's not found, it tests for DMA64_PROPNAME.

This approach will skip scanning for DMA64_PROPNAME if
DIRECT64_PROPNAME was found, as both may not exist in the same node.
But for this approach to work we need remove_ddw() to return error if
the property is not found.

Does it make sense? or should I just test for both?

Best regards,
Leonardo Bras