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Re: [Qemu-devel] [PATCH v3] pci: Introduce helper to retrieve a PCI devi
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH v3] pci: Introduce helper to retrieve a PCI device's DMA address space |
Date: |
Sun, 11 Aug 2013 16:58:47 +0300 |
On Sat, Aug 10, 2013 at 01:09:08AM +1000, Alexey Kardashevskiy wrote:
> A PCI device's DMA address space (possibly an IOMMU) is returned by a
> method on the PCIBus. At the moment that only has one caller, so the
> method is simply open coded. We'll need another caller for VFIO, so
> this patch introduces a helper/wrapper function.
>
> If IOMMU is not set, the pci_device_iommu_address_space() function
> returns the parent's IOMMU skipping the "bus master" address space as
> otherwise proper emulation would require more effort for no benefit.
>
> Signed-off-by: David Gibson <address@hidden>
> [aik: added inheritance from parent if iommu is not set for the current bus]
> Signed-off-by: Alexey Kardashevskiy <address@hidden>
>
> ---
> Changes:
> v3:
> * added comment about ignoring bus master address space
>
> v2:
> * added inheritance, needed for a pci-bridge on spapr-ppc64
> * pci_iommu_as renamed to pci_device_iommu_address_space
> ---
> hw/pci/pci.c | 24 ++++++++++++++++++------
> include/hw/pci/pci.h | 1 +
> 2 files changed, 19 insertions(+), 6 deletions(-)
>
> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> index 4c004f5..dbfa395 100644
> --- a/hw/pci/pci.c
> +++ b/hw/pci/pci.c
> @@ -812,12 +812,7 @@ static PCIDevice *do_pci_register_device(PCIDevice
> *pci_dev, PCIBus *bus,
> }
>
> pci_dev->bus = bus;
> - if (bus->iommu_fn) {
> - dma_as = bus->iommu_fn(bus, bus->iommu_opaque, devfn);
> - } else {
> - /* FIXME: inherit memory region from bus creator */
> - dma_as = &address_space_memory;
> - }
> + dma_as = pci_device_iommu_address_space(pci_dev);
>
> memory_region_init_alias(&pci_dev->bus_master_enable_region,
> OBJECT(pci_dev), "bus master",
> @@ -2239,6 +2234,23 @@ static void pci_device_class_init(ObjectClass *klass,
> void *data)
> k->props = pci_props;
> }
>
> +AddressSpace *pci_device_iommu_address_space(PCIDevice *dev)
> +{
> + PCIBus *bus = PCI_BUS(dev->bus);
> +
> + if (bus->iommu_fn) {
> + return bus->iommu_fn(bus, bus->iommu_opaque, dev->devfn);
> + }
> +
> + if (bus->parent_dev) {
> + /** We are ignoring the bus master DMA bit of the bridge
> + * as it would complicate things such as VFIO for no good reason */
/*
* Always
* like
* this
*/
/** Never
* like this */
The comment should be improved I think.
I would put it like this:
/*
* Note: this does not check bus master enable bit on device or
* any of the pci to pci bridges above it, it's up to the caller to
* check that before initiating the transaction.
*
* TODO: design a mechanism for callers to do this without
* doing bus scans on data path.
*/
Would you like me to queue this on the pci tree? If yes I can
tweak the comment myself, no need to repost.
> + return pci_device_iommu_address_space(bus->parent_dev);
> + }
> +
> + return &address_space_memory;
> +}
> +
> void pci_setup_iommu(PCIBus *bus, PCIIOMMUFunc fn, void *opaque)
> {
> bus->iommu_fn = fn;
> diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
> index ccec2ba..2374aa9 100644
> --- a/include/hw/pci/pci.h
> +++ b/include/hw/pci/pci.h
> @@ -405,6 +405,7 @@ void pci_device_deassert_intx(PCIDevice *dev);
>
> typedef AddressSpace *(*PCIIOMMUFunc)(PCIBus *, void *, int);
>
> +AddressSpace *pci_device_iommu_address_space(PCIDevice *dev);
> void pci_setup_iommu(PCIBus *bus, PCIIOMMUFunc fn, void *opaque);
>
> static inline void
> --
> 1.8.3.2