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From:   Rob Herring <robh@kernel.org>
Date:   Mon, 9 May 2022 14:27:19 -0500
Message-ID: <CAL_JsqLSt4n2LMC_Rcz01jYdzeAVM0aodBibSNxOcqt1m0vJfw@mail.gmail.com>
Subject: Re: [PATCH v2] iommu/dma: Explicitly sort PCI DMA windows
To:     Robin Murphy <robin.murphy@arm.com>
Cc:     Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Linux IOMMU <iommu@lists.linux-foundation.org>,
        PCI <linux-pci@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Mon, May 9, 2022 at 5:16 AM Robin Murphy <robin.murphy@arm.com> wrote:
>
> Originally, creating the dma_ranges resource list in pre-sorted fashion
> was the simplest and most efficient way to enforce the order required by
> iova_reserve_pci_windows(). However since then at least one PCI host
> driver is now re-sorting the list for its own probe-time processing,
> which doesn't seem entirely unreasonable, so that basic assumption no
> longer holds. Make iommu-dma robust and get the sort order it needs by
> explicitly sorting, which means we can also save the effort at creation
> time and just build the list in whatever natural order the DT had.
>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
>
> v2: Clean up now-unused local variable
>
>  drivers/iommu/dma-iommu.c | 13 ++++++++++++-
>  drivers/pci/of.c          |  8 +-------
>  2 files changed, 13 insertions(+), 8 deletions(-)

Reviewed-by: Rob Herring <robh@kernel.org>