From: Leonardo Bras <leobras.c@gmail.com>
To: Brian King <brking@linux.vnet.ibm.com>,
Alexey Kardashevskiy <aik@ozlabs.ru>,
Michael Ellerman <mpe@ellerman.id.au>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>, Joel Stanley <joel@jms.id.au>,
Christophe Leroy <christophe.leroy@c-s.fr>,
Thiago Jung Bauermann <bauerman@linux.ibm.com>,
Ram Pai <linuxram@us.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 5/7] powerpc/iommu: Move iommu_table cleaning routine to iommu_table_clean
Date: Wed, 22 Jul 2020 20:45:25 -0300 [thread overview]
Message-ID: <e23c8ffd6667e675ab80c83c39f8b91beb591328.camel@gmail.com> (raw)
In-Reply-To: <d6078fce-bb5f-f829-5de2-5bce3cee2bd5@linux.vnet.ibm.com>
On Tue, 2020-07-21 at 19:52 -0500, Brian King wrote:
> >
> > As of today, there seems to be nothing like that happening in the
> > driver I am testing.
> > I spoke to Brian King on slack, and he mentioned that at the point DDW
> > is created there should be no allocations in place.
>
> I think there are a couple of scenarios here. One is where there is a DMA
> allocation prior to a call to set the DMA mask. Second scenario is if the
> driver makes multiple calls to set the DMA mask. I would argue that a properly
> written driver should tell the IOMMU subsystem what DMA mask it supports prior
> to allocating DMA memroy. Documentation/core-api/dma-api-howto.rst should
> describe what is legal and what is not.
>
> It might be reasonable to declare its not allowed to allocate DMA memory
> and then later change the DMA mask and clearly call this out in the documentation
> if its not already.
>
> -Brian
Thank you for the feedback Brian!
That makes sense to me. I will try to have this in mind for the next
patchset.
Best regards,
next prev parent reply other threads:[~2020-07-22 23:45 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-16 7:16 [PATCH v4 0/7] Remove default DMA window before creating DDW Leonardo Bras
2020-07-16 7:16 ` [PATCH v4 1/7] powerpc/pseries/iommu: Create defines for operations in ibm,ddw-applicable Leonardo Bras
2020-08-04 21:27 ` [PATCH v4 1/7] powerpc/pseries/iommu: Create defines for operations in ibm, ddw-applicable David Dai
2020-08-04 21:34 ` David Dai
2020-07-16 7:16 ` [PATCH v4 2/7] powerpc/pseries/iommu: Update call to ibm,query-pe-dma-windows Leonardo Bras
2020-08-04 21:31 ` [PATCH v4 2/7] powerpc/pseries/iommu: Update call to ibm, query-pe-dma-windows David Dai
2020-07-16 7:16 ` [PATCH v4 3/7] powerpc/pseries/iommu: Move window-removing part of remove_ddw into remove_dma_window Leonardo Bras
2020-08-04 21:32 ` David Dai
2020-07-16 7:16 ` [PATCH v4 4/7] powerpc/pseries/iommu: Remove default DMA window before creating DDW Leonardo Bras
2020-08-04 21:33 ` David Dai
2020-07-16 7:16 ` [PATCH v4 5/7] powerpc/iommu: Move iommu_table cleaning routine to iommu_table_clean Leonardo Bras
2020-07-21 4:59 ` Alexey Kardashevskiy
2020-07-21 22:13 ` Leonardo Bras
2020-07-22 0:52 ` Brian King
2020-07-22 23:45 ` Leonardo Bras [this message]
2020-07-22 1:28 ` Alexey Kardashevskiy
2020-07-22 23:37 ` Leonardo Bras
2020-07-16 7:16 ` [PATCH v4 6/7] powerpc/pseries/iommu: Make use of DDW even if it does not map the partition Leonardo Bras
2020-07-21 21:39 ` Leonardo Bras
2020-07-16 7:16 ` [PATCH v4 7/7] powerpc/pseries/iommu: Rename "direct window" to "dma window" Leonardo Bras
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