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Re: [Qemu-arm] [PATCH 2/2] arm/virt: Mark pcie controller node as dma-co

From: Peter Maydell
Subject: Re: [Qemu-arm] [PATCH 2/2] arm/virt: Mark pcie controller node as dma-coherent
Date: Thu, 2 Jun 2016 13:32:39 +0100

On 2 June 2016 at 13:26, Bogdan Purcareata <address@hidden> wrote:
> A PCI device is marked either as coherent or non-coherent based on the pcie
> controller "dma-coherent" property. This is further used when configuring the
> IOMMU ops for the device DMA resources (e.g. descriptor rings, for e1000e).
> This dma-coherent property needs to be configured in the guest environment,
> in case there's a directly assigned VFIO PCI device. Since the guest only
> receives one emulated pcie controller bus - regardless of the host
> configuration - add this property if there's at least one host pcie host
> controller that is DMA coherent (this implies that the host interconnect
> is coherent as well).

This patch seems to change the property of the emulated PCIe controller
based on the host PCIe controller even if we're not doing any PCIe
passthrough at all. That seems definitely wrong to me.

(Should the purely-emulated case be marked DMA-coherent anyway?
I forget the fiddly details...)

-- PMM

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