Re: [Qemu-devel] [PATCH v1] pci: Set PCI-bus device entry before initializing bus master

[Yi Min Zhao <zyimin@linux.vnet.ibm.com>]

I strongly agree. This will make IOMMU assignment easier.


在 2017/10/5 下午8:36, Pierre Morel 写道:
> When initializing the PCI-bus master pci_init_bus_master(PCIDevice *)
> calls pci_device_iommu_address_space(PCIDevice *) which in turn calls
> iommu_bus->iommu_fn(bus, opaque,devfn)
>
> If the device entry of the PCI-bus is not initialized to point to the
> PCIDevice structure, the iommu_fn() function, getting only bus and
> devno, is unable to retrieve the PCIDevice.
>
> Usually it is not a problem as the DMA address space is depending of
> the BUS but in an architecture like S390, each PCI Device can have
> its own DMA address space.
> Being able to setup the DMA address space at the right moment will
> greatly simplify the implementation.
>
> This patch proposes to setup the bus device entry before calling
> pci_init_bus_master() and reset the entry in case of error.
>
> Signed-off-by: Pierre Morel <pmorel@linux.vnet.ibm.com>
> ---
>   hw/pci/pci.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> index 1e6fb88..3e64492 100644
> --- a/hw/pci/pci.c
> +++ b/hw/pci/pci.c
> @@ -1026,6 +1026,7 @@ static PCIDevice *do_pci_register_device(PCIDevice *pci_dev, PCIBus *bus,
>       address_space_init(&pci_dev->bus_master_as,
>                          &pci_dev->bus_master_container_region, pci_dev->name);
>
> +    bus->devices[devfn] = pci_dev;
>       if (qdev_hotplug) {
>           pci_init_bus_master(pci_dev);
>       }
> @@ -1062,6 +1063,7 @@ static PCIDevice *do_pci_register_device(PCIDevice *pci_dev, PCIBus *bus,
>       if (local_err) {
>           error_propagate(errp, local_err);
>           do_pci_unregister_device(pci_dev);
> +        bus->devices[devfn] = NULL;
>           return NULL;
>       }
>
> @@ -1071,7 +1073,6 @@ static PCIDevice *do_pci_register_device(PCIDevice *pci_dev, PCIBus *bus,
>           config_write = pci_default_write_config;
>       pci_dev->config_read = config_read;
>       pci_dev->config_write = config_write;
> -    bus->devices[devfn] = pci_dev;
>       pci_dev->version_id = 2; /* Current pci device vmstate version */
>       return pci_dev;
>   }