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Re: [Qemu-devel] [PATCH v2] pci: Introduce helper to retrieve a PCI devi
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v2] pci: Introduce helper to retrieve a PCI device's DMA address space |
Date: |
Fri, 09 Aug 2013 12:19:51 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 |
Il 09/08/2013 12:13, Alexey Kardashevskiy ha scritto:
> On 08/09/2013 07:53 PM, Paolo Bonzini wrote:
>> Il 09/08/2013 11:48, Alexey Kardashevskiy ha scritto:
>>> On 08/09/2013 07:40 PM, Paolo Bonzini wrote:
>>>> Il 09/08/2013 10:49, Alexey Kardashevskiy ha scritto:
>>>>> 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.
>>>>>
>>>>> 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:
>>>>> 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 | 22 ++++++++++++++++------
>>>>> include/hw/pci/pci.h | 1 +
>>>>> 2 files changed, 17 insertions(+), 6 deletions(-)
>>>>>
>>>>> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
>>>>> index 4c004f5..0072b54 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 +2234,21 @@ 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) {
>>>>> + return pci_device_iommu_address_space(bus->parent_dev);
>>>>> + }
>>>>
>>>> No, this would fail if bus->parent_dev is not NULL but not a PCI device
>>>> either.
>>>
>>> parent_dev is of the PCIDevice* type, how can it be not a PCI device? :-/
>>
>> Doh, I misread the code, I thought it was the "parent" field in
>> BusState. Why do we have parent_dev at all?
>
> The code is too old? Don't know.
>
>
>>>> You can use object_dynamic_cast to convert the parent_dev to
>>>> PCIDevice, and if the cast succeeds you call the new function.
>>>>
>>>> Perhaps you could make the new function take a PCIBus instead.
>>>> Accessing the PCIDevice's IOMMU address space (as opposed to the
>>>> bus-master address space) doesn't make much sense, VFIO is really a
>>>> special case. Putting the new API on the bus side instead looks better.
>>>>
>>>> (BTW, do you need to enable bus-master DMA on PCI bridges, to do DMA for
>>>> devices sitting on the secondary bus?)
>>>
>>> It happens naturally I guess when linux enables devices.
>>
>> Yes, but then using the IOMMU address space would be wrong; you would
>> have to use the bus-master address space as a base for the child's
>> bus-master address space.
>
>
> Like this? Works too.
>
> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> index 8bdcedc..a4c70e6 100644
> --- a/hw/pci/pci.c
> +++ b/hw/pci/pci.c
> @@ -2247,23 +2247,23 @@ 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) {
> return pci_device_iommu_address_space(bus->parent_dev);
> }
>
> - return &address_space_memory;
> + return &dev->bus_master_as;
> }
I was thinking more like this:
if (bus->parent_dev) {
- return pci_device_iommu_address_space(bus->parent_dev);
+ /* Take parent device's bus-master enable bit into account. */
+ return pci_get_address_space(bus->parent_dev);
}
+ /* Not a secondary bus and no IOMMU. Use system memory. */
return &address_space_memory;
Paolo
>
>
>> Also, we would have to fix the x86 firmware.
>>
>> Paolo
>>
>
>
- [Qemu-devel] [PATCH v2] pci: Introduce helper to retrieve a PCI device's DMA address space, Alexey Kardashevskiy, 2013/08/09
- Re: [Qemu-devel] [PATCH v2] pci: Introduce helper to retrieve a PCI device's DMA address space, Paolo Bonzini, 2013/08/09
- Re: [Qemu-devel] [PATCH v2] pci: Introduce helper to retrieve a PCI device's DMA address space, Alexey Kardashevskiy, 2013/08/09
- Re: [Qemu-devel] [PATCH v2] pci: Introduce helper to retrieve a PCI device's DMA address space, Paolo Bonzini, 2013/08/09
- Re: [Qemu-devel] [PATCH v2] pci: Introduce helper to retrieve a PCI device's DMA address space, Alexey Kardashevskiy, 2013/08/09
- Re: [Qemu-devel] [PATCH v2] pci: Introduce helper to retrieve a PCI device's DMA address space,
Paolo Bonzini <=
- Re: [Qemu-devel] [PATCH v2] pci: Introduce helper to retrieve a PCI device's DMA address space, Alexey Kardashevskiy, 2013/08/09
- Re: [Qemu-devel] [PATCH v2] pci: Introduce helper to retrieve a PCI device's DMA address space, Paolo Bonzini, 2013/08/09
- Re: [Qemu-devel] [PATCH v2] pci: Introduce helper to retrieve a PCI device's DMA address space, Alexey Kardashevskiy, 2013/08/09
- Re: [Qemu-devel] [PATCH v2] pci: Introduce helper to retrieve a PCI device's DMA address space, Paolo Bonzini, 2013/08/09
- Re: [Qemu-devel] [PATCH v2] pci: Introduce helper to retrieve a PCI device's DMA address space, David Gibson, 2013/08/09
Re: [Qemu-devel] [PATCH v2] pci: Introduce helper to retrieve a PCI device's DMA address space, Benjamin Herrenschmidt, 2013/08/09