Re: [PATCH v4 01/15] hw/pci: Add a pci_setup_iommu_ops() helper

[Joao Martins <joao.m.martins@oracle.com>]

On 06/10/2023 09:50, Cédric Le Goater wrote:
> On 10/6/23 10:38, Joao Martins wrote:
>> On 02/10/2023 16:12, Cédric Le Goater wrote:
>>> Hello Joao,
>>>
>>> On 6/22/23 23:48, Joao Martins wrote:
>>>> From: Yi Liu <yi.l.liu@intel.com>
>>>>
>>>> Add a pci_setup_iommu_ops() that uses a newly added structure
>>>> (PCIIOMMUOps) instead of using PCIIOMMUFunc. The old pci_setup_iommu()
>>>> that uses PCIIOMMUFunc is still kept for other IOMMUs to get an
>>>> an address space for a PCI device in vendor specific way.
>>>>
>>>> In preparation to expand to supplying vIOMMU attributes, add a
>>>> alternate helper pci_setup_iommu_ops() to setup the PCI device IOMMU.
>>>> For now the PCIIOMMUOps just defines the address_space, but it will
>>>> be extended to have another callback.
>>>>
>>>> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
>>>> [joao: Massage commit message and subject, and make it a complementary
>>>> rather than changing every single consumer of pci_setup_iommu()]
>>>> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
>>>> ---
>>>> v1: https://lore.kernel.org/all/20210302203827.437645-5-yi.l.liu@intel.com/
>>>> ---
>>>>    include/hw/pci/pci.h     |  7 +++++++
>>>>    include/hw/pci/pci_bus.h |  1 +
>>>>    hw/pci/pci.c             | 26 +++++++++++++++++++++++---
>>>>    3 files changed, 31 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
>>>> index e6d0574a2999..f59aef5a329a 100644
>>>> --- a/include/hw/pci/pci.h
>>>> +++ b/include/hw/pci/pci.h
>>>> @@ -368,6 +368,13 @@ typedef AddressSpace *(*PCIIOMMUFunc)(PCIBus *, void *,
>>>> int);
>>>>    AddressSpace *pci_device_iommu_address_space(PCIDevice *dev);
>>>>    void pci_setup_iommu(PCIBus *bus, PCIIOMMUFunc fn, void *opaque);
>>>>    +typedef struct PCIIOMMUOps PCIIOMMUOps;
>>>> +struct PCIIOMMUOps {
>>>> +    AddressSpace * (*get_address_space)(PCIBus *bus,
>>>> +                                void *opaque, int32_t devfn);
>>>> +};
>>>> +void pci_setup_iommu_ops(PCIBus *bus, const PCIIOMMUOps *iommu_ops, void
>>>> *opaque);
>>>> +
>>>
>>> I think you should first convert all PHBs to PCIIOMMUOps to avoid all the
>>> tests as below and adapt pci_setup_iommu_ops() with the new parameter.
>>>
>>
>> OK, that's Yi's original patch:
>>
>> https://lore.kernel.org/all/20210302203827.437645-5-yi.l.liu@intel.com/
>>
>> I went with this one is that 1) it might take eons to get every single IOMMU
>> maintainer ack; and 2) it would allow each IOMMU to move at its own speed
>> specially as I can't test most of the other ones. essentially iterative, rather
>> than invasive change? Does that make sense?
> 
> I think it is ok to make global changes to replace a function by a struct
> of ops. This is not major (unless the extra indirection has a major perf
> impact on some platforms). 

It should be a mechanical change. As the pci_setup_iommu_ops() should be
functionally equivalent to pci_setup_iommu() [...]

> Getting acks from everyone will be difficult
> since some PHBs are orphans.

[...] This is what gets me a bit hesitant