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Re: [Qemu-devel] [PATCH 2/2] arm/virt: Mark pcie controller node as dma-
From: |
Mihai Claudiu Caraman |
Subject: |
Re: [Qemu-devel] [PATCH 2/2] arm/virt: Mark pcie controller node as dma-coherent |
Date: |
Fri, 3 Jun 2016 14:22:48 +0000 |
> -----Original Message-----
> From: Qemu-devel [mailto:address@hidden On Behalf Of Peter Maydell
> Sent: Thursday, June 02, 2016 3:33 PM
> To: Bogdan Purcareata <address@hidden>
> Cc: QEMU Developers <address@hidden>; Peter Crosthwaite <address@hidden>;
> Alexander Graf <address@hidden>; qemu-arm <address@hidden>; Eric Auger
> <address@hidden>
> Subject: Re: [Qemu-devel] [PATCH 2/2] arm/virt: Mark pcie controller node as
> dma-coherent
>
> 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...)
>
> thanks
> -- PMM
In particular for virtual and emulated devices the host CPU behaves as a DMA
coherent 'device'. This should have been stated in patch description.
Regards,
Mike
- [Qemu-devel] [PATCH 0/2] arm/virt: Propagate pcie DMA coherency, Bogdan Purcareata, 2016/06/02
- [Qemu-devel] [PATCH 2/2] arm/virt: Mark pcie controller node as dma-coherent, Bogdan Purcareata, 2016/06/02
- Re: [Qemu-devel] [PATCH 2/2] arm/virt: Mark pcie controller node as dma-coherent, Peter Maydell, 2016/06/02
- Re: [Qemu-devel] [PATCH 2/2] arm/virt: Mark pcie controller node as dma-coherent, Alexander Graf, 2016/06/02
- Re: [Qemu-devel] [PATCH 2/2] arm/virt: Mark pcie controller node as dma-coherent, Auger Eric, 2016/06/07
- Re: [Qemu-devel] [PATCH 2/2] arm/virt: Mark pcie controller node as dma-coherent, Ard Biesheuvel, 2016/06/16
- Re: [Qemu-devel] [PATCH 2/2] arm/virt: Mark pcie controller node as dma-coherent, Peter Maydell, 2016/06/28
- Re: [Qemu-devel] [PATCH 2/2] arm/virt: Mark pcie controller node as dma-coherent, Bogdan Purcareata, 2016/06/29
- Re: [Qemu-devel] [PATCH 2/2] arm/virt: Mark pcie controller node as dma-coherent,
Mihai Claudiu Caraman <=
- Re: [Qemu-devel] [PATCH 2/2] arm/virt: Mark pcie controller node as dma-coherent, Peter Maydell, 2016/06/03
- Re: [Qemu-devel] [PATCH 2/2] arm/virt: Mark pcie controller node as dma-coherent, agraf, 2016/06/03
- Re: [Qemu-devel] [PATCH 2/2] arm/virt: Mark pcie controller node as dma-coherent, Mihai Claudiu Caraman, 2016/06/03
- Re: [Qemu-devel] [PATCH 2/2] arm/virt: Mark pcie controller node as dma-coherent, Alexander Graf, 2016/06/03
- Re: [Qemu-devel] [PATCH 2/2] arm/virt: Mark pcie controller node as dma-coherent, Mihai Claudiu Caraman, 2016/06/03
[Qemu-devel] [PATCH 1/2] device_tree: introduce qemu_fdt_node_path_prop, Bogdan Purcareata, 2016/06/02