Re: [PATCH rfcv1 2/6] hw/pci: introduce pci_device_set/unset_iommu_device()

[Eric Auger]

On 1/23/24 10:25, Duan, Zhenzhong wrote:
>
>> -----Original Message-----
>> From: Cédric Le Goater <clg@redhat.com>
>> Subject: Re: [PATCH rfcv1 2/6] hw/pci: introduce
>> pci_device_set/unset_iommu_device()
>>
>> On 1/23/24 07:37, Duan, Zhenzhong wrote:
>>>
>>>> -----Original Message-----
>>>> From: Cédric Le Goater <clg@redhat.com>
>>>> Subject: Re: [PATCH rfcv1 2/6] hw/pci: introduce
>>>> pci_device_set/unset_iommu_device()
>>>>
>>>> On 1/15/24 11:13, Zhenzhong Duan wrote:
>>>>> From: Yi Liu <yi.l.liu@intel.com>
>>>>>
>>>>> This adds pci_device_set/unset_iommu_device() to set/unset
>>>>> IOMMUFDDevice for a given PCIe device. Caller of set
>>>>> should fail if set operation fails.
>>>>>
>>>>> Extract out pci_device_get_iommu_bus_devfn() to facilitate
>>>>> implementation of pci_device_set/unset_iommu_device().
>>>>>
>>>>> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
>>>>> Signed-off-by: Yi Sun <yi.y.sun@linux.intel.com>
>>>>> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
>>>>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
>>>>> ---
>>>>>    include/hw/pci/pci.h | 39
>> ++++++++++++++++++++++++++++++++++-
>>>>>    hw/pci/pci.c         | 49
>>>> +++++++++++++++++++++++++++++++++++++++++++-
>>>>>    2 files changed, 86 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
>>>>> index fa6313aabc..a810c0ec74 100644
>>>>> --- a/include/hw/pci/pci.h
>>>>> +++ b/include/hw/pci/pci.h
>>>>> @@ -7,6 +7,8 @@
>>>>>    /* PCI includes legacy ISA access.  */
>>>>>    #include "hw/isa/isa.h"
>>>>>
>>>>> +#include "sysemu/iommufd_device.h"
>>>>> +
>>>>>    extern bool pci_available;
>>>>>
>>>>>    /* PCI bus */
>>>>> @@ -384,10 +386,45 @@ typedef struct PCIIOMMUOps {
>>>>>         *
>>>>>         * @devfn: device and function number
>>>>>         */
>>>>> -   AddressSpace * (*get_address_space)(PCIBus *bus, void *opaque, int
>>>> devfn);
>>>>> +    AddressSpace * (*get_address_space)(PCIBus *bus, void *opaque,
>> int
>>>> devfn);
>>>>> +    /**
>>>>> +     * @set_iommu_device: set iommufd device for a PCI device to
>>>> vIOMMU
>>>>> +     *
>>>>> +     * Optional callback, if not implemented in vIOMMU, then vIOMMU
>>>> can't
>>>>> +     * utilize iommufd specific features.
>>>>> +     *
>>>>> +     * Return true if iommufd device is accepted, or else return false 
>>>>> with
>>>>> +     * errp set.
>>>>> +     *
>>>>> +     * @bus: the #PCIBus of the PCI device.
>>>>> +     *
>>>>> +     * @opaque: the data passed to pci_setup_iommu().
>>>>> +     *
>>>>> +     * @devfn: device and function number of the PCI device.
>>>>> +     *
>>>>> +     * @idev: the data structure representing iommufd device.
>>>>> +     *
>>>>> +     */
>>>>> +    int (*set_iommu_device)(PCIBus *bus, void *opaque, int32_t devfn,
>>>>> +                            IOMMUFDDevice *idev, Error **errp);
>>>>> +    /**
>>>>> +     * @unset_iommu_device: unset iommufd device for a PCI device
>> from
>>>> vIOMMU
>>>>> +     *
>>>>> +     * Optional callback.
>>>>> +     *
>>>>> +     * @bus: the #PCIBus of the PCI device.
>>>>> +     *
>>>>> +     * @opaque: the data passed to pci_setup_iommu().
>>>>> +     *
>>>>> +     * @devfn: device and function number of the PCI device.
>>>>> +     */
>>>>> +    void (*unset_iommu_device)(PCIBus *bus, void *opaque, int32_t
>>>> devfn);
>>>>>    } PCIIOMMUOps;
>>>>>
>>>>>    AddressSpace *pci_device_iommu_address_space(PCIDevice *dev);
>>>>> +int pci_device_set_iommu_device(PCIDevice *dev, IOMMUFDDevice
>>>> *idev,
>>>>> +                                Error **errp);
>>>>> +void pci_device_unset_iommu_device(PCIDevice *dev);
>>>>>
>>>>>    /**
>>>>>     * pci_setup_iommu: Initialize specific IOMMU handlers for a PCIBus
>>>>> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
>>>>> index 76080af580..3848662f95 100644
>>>>> --- a/hw/pci/pci.c
>>>>> +++ b/hw/pci/pci.c
>>>>> @@ -2672,7 +2672,10 @@ static void
>>>> pci_device_class_base_init(ObjectClass *klass, void *data)
>>>>>        }
>>>>>    }
>>>>>
>>>>> -AddressSpace *pci_device_iommu_address_space(PCIDevice *dev)
>>>>> +static void pci_device_get_iommu_bus_devfn(PCIDevice *dev,
>>>>> +                                           PCIBus **aliased_pbus,
>>>>> +                                           PCIBus **piommu_bus,
>>>>> +                                           uint8_t *aliased_pdevfn)
>>>>>    {
>>>>>        PCIBus *bus = pci_get_bus(dev);
>>>>>        PCIBus *iommu_bus = bus;
>>>>> @@ -2717,6 +2720,18 @@ AddressSpace
>>>> *pci_device_iommu_address_space(PCIDevice *dev)
>>>>>            iommu_bus = parent_bus;
>>>>>        }
>>>>> +    *aliased_pbus = bus;
>>>>> +    *piommu_bus = iommu_bus;
>>>>> +    *aliased_pdevfn = devfn;
>>>>> +}
>>>>> +
>>>>> +AddressSpace *pci_device_iommu_address_space(PCIDevice *dev)
>>>>> +{
>>>>> +    PCIBus *bus;
>>>>> +    PCIBus *iommu_bus;
>>>>> +    uint8_t devfn;
>>>>> +
>>>>> +    pci_device_get_iommu_bus_devfn(dev, &bus, &iommu_bus,
>> &devfn);
>>>>>        if (!pci_bus_bypass_iommu(bus) && iommu_bus->iommu_ops) {
>>>>>            return iommu_bus->iommu_ops->get_address_space(bus,
>>>>>                                     iommu_bus->iommu_opaque, devfn);
>>>>> @@ -2724,6 +2739,38 @@ AddressSpace
>>>> *pci_device_iommu_address_space(PCIDevice *dev)
>>>>>        return &address_space_memory;
>>>>>    }
>>>>>
>>>>> +int pci_device_set_iommu_device(PCIDevice *dev, IOMMUFDDevice
>>>> *idev,
>>>>> +                                Error **errp)
>>>>> +{
>>>>> +    PCIBus *bus;
>>>>> +    PCIBus *iommu_bus;
>>>>> +    uint8_t devfn;
>>>>> +
>>>>> +    pci_device_get_iommu_bus_devfn(dev, &bus, &iommu_bus,
>> &devfn);
>>>>> +    if (!pci_bus_bypass_iommu(bus) && iommu_bus &&
>>>> Why do we test iommu_bus in pci_device_un/set_iommu_device
>> routines
>>>> and
>>>> not in pci_device_iommu_address_space() ?
>>> iommu_bus check in pci_device_iommu_address_space() is dropped in
>>> below commit, I didn't find related discussion in mail history, maybe
>>> by accident? I can add it back if it's not intentional.
>> Can iommu_bus be NULL or should we add an assert ?
> I dig into the history changes of pci_device_iommu_address_space() and
> below commit added iommu_bus check.
>
> 5af2ae230514  pci: Fix pci_device_iommu_address_space() bus propagation
>
> In theory, !iommu_bus->parent_dev take precedency over !iommu_bus,
> So we never see iommu_bus NULL, assert may be better.

I think we had such a discussion in
https://www.mail-archive.com/qemu-devel@nongnu.org/msg994766.html
But maybe this was related to a different call place. I remember I
challenged the check at some point

Eric
>
> Thanks
> Zhenzhong
>