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From: Marc Zyngier <maz@kernel.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: robh@kernel.org, linux-pci@vger.kernel.org,
	iommu@lists.linux-foundation.org, dann.frazier@canonical.com,
	bhelgaas@google.com, will@kernel.org
Subject: Re: [PATCH] iommu/dma: Explicitly sort PCI DMA windows
Date: Wed, 23 Mar 2022 09:49:04 +0000	[thread overview]
Message-ID: <874k3pxalr.wl-maz@kernel.org> (raw)
In-Reply-To: <65657c5370fa0161739ba094ea948afdfa711b8a.1647967875.git.robin.murphy@arm.com>

On Tue, 22 Mar 2022 17:27:36 +0000,
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>
> ---
> 
> Looking at this area off the back of the XGene thread[1] made me realise
> that we need to do it anyway, regardless of whether it might also happen
> to restore the previous XGene behaviour or not. Presumably nobody's
> tried to use pcie-cadence-host behind an IOMMU yet...

This definitely restores PCIe functionality on my Mustang (XGene-1).
Hopefully dann can comment on whether this addresses his own issue, as
his firmware is significantly different.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <maz@kernel.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: joro@8bytes.org, will@kernel.org,
	iommu@lists.linux-foundation.org, bhelgaas@google.com,
	linux-pci@vger.kernel.org, robh@kernel.org,
	dann.frazier@canonical.com
Subject: Re: [PATCH] iommu/dma: Explicitly sort PCI DMA windows
Date: Wed, 23 Mar 2022 09:49:04 +0000	[thread overview]
Message-ID: <874k3pxalr.wl-maz@kernel.org> (raw)
In-Reply-To: <65657c5370fa0161739ba094ea948afdfa711b8a.1647967875.git.robin.murphy@arm.com>

On Tue, 22 Mar 2022 17:27:36 +0000,
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>
> ---
> 
> Looking at this area off the back of the XGene thread[1] made me realise
> that we need to do it anyway, regardless of whether it might also happen
> to restore the previous XGene behaviour or not. Presumably nobody's
> tried to use pcie-cadence-host behind an IOMMU yet...

This definitely restores PCIe functionality on my Mustang (XGene-1).
Hopefully dann can comment on whether this addresses his own issue, as
his firmware is significantly different.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

  reply	other threads:[~2022-03-23  9:49 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-22 17:27 [PATCH] iommu/dma: Explicitly sort PCI DMA windows Robin Murphy
2022-03-22 17:27 ` Robin Murphy
2022-03-23  9:49 ` Marc Zyngier [this message]
2022-03-23  9:49   ` Marc Zyngier
2022-03-23 22:15   ` dann frazier
2022-03-23 22:15     ` dann frazier
2022-03-24  0:55     ` Rob Herring
2022-03-24  0:55       ` Rob Herring
2022-03-24  3:09       ` dann frazier
2022-03-24  3:09         ` dann frazier
2022-03-24  0:56 ` Rob Herring
2022-03-24  0:56   ` Rob Herring
2022-03-24 10:08   ` Robin Murphy
2022-03-24 10:08     ` Robin Murphy

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