Re: [PATCH 3/3] s390x/pci: drive ISM reset from subsystem reset

[Matthew Rosato]

On 1/17/24 6:01 AM, Cédric Le Goater wrote:
> Adding Alex,
> 
> On 1/16/24 23:31, Matthew Rosato wrote:
>> ISM devices are sensitive to manipulation of the IOMMU, so the ISM device
>> needs to be reset before the vfio-pci device is reset (triggering a full
>> UNMAP).  In order to ensure this occurs, trigger ISM device resets from
>> subsystem_reset before triggering the PCI bus reset (which will also
>> trigger vfio-pci reset).  This only needs to be done for ISM devices
>> which were enabled for use by the guest.
>> Further, ensure that AIF is disabled as part of the reset event.
>>
>> Fixes: ef1535901a ("s390x: do a subsystem reset before the unprotect on 
>> reboot")
>> Fixes: 03451953c7 ("s390x/pci: reset ISM passthrough devices on shutdown and 
>> system reset")
>> Reported-by: Cédric Le Goater <clg@redhat.com>
>> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
>> ---
>>   hw/s390x/s390-pci-bus.c         | 26 +++++++++++++++++---------
>>   hw/s390x/s390-virtio-ccw.c      |  2 ++
>>   include/hw/s390x/s390-pci-bus.h |  1 +
>>   3 files changed, 20 insertions(+), 9 deletions(-)
>>
>> diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
>> index 347580ebac..3e57d5faca 100644
>> --- a/hw/s390x/s390-pci-bus.c
>> +++ b/hw/s390x/s390-pci-bus.c
>> @@ -151,20 +151,12 @@ static void s390_pci_shutdown_notifier(Notifier *n, 
>> void *opaque)
>>       pci_device_reset(pbdev->pdev);
>>   }
>>   -static void s390_pci_reset_cb(void *opaque)
>> -{
>> -    S390PCIBusDevice *pbdev = opaque;
>> -
>> -    pci_device_reset(pbdev->pdev);
>> -}
>> -
>>   static void s390_pci_perform_unplug(S390PCIBusDevice *pbdev)
>>   {
>>       HotplugHandler *hotplug_ctrl;
>>         if (pbdev->pft == ZPCI_PFT_ISM) {
>>           notifier_remove(&pbdev->shutdown_notifier);
>> -        qemu_unregister_reset(s390_pci_reset_cb, pbdev);
>>       }
>>         /* Unplug the PCI device */
>> @@ -1132,7 +1124,6 @@ static void s390_pcihost_plug(HotplugHandler 
>> *hotplug_dev, DeviceState *dev,
>>               if (pbdev->pft == ZPCI_PFT_ISM) {
>>                   pbdev->shutdown_notifier.notify = 
>> s390_pci_shutdown_notifier;
>>                   qemu_register_shutdown_notifier(&pbdev->shutdown_notifier);
>> -                qemu_register_reset(s390_pci_reset_cb, pbdev);
>>               }
>>           } else {
>>               pbdev->fh |= FH_SHM_EMUL;
>> @@ -1279,6 +1270,23 @@ static void s390_pci_enumerate_bridge(PCIBus *bus, 
>> PCIDevice *pdev,
>>       pci_default_write_config(pdev, PCI_SUBORDINATE_BUS, s->bus_no, 1);
>>   }
>>   +void s390_pci_ism_reset(void)
>> +{
>> +    S390pciState *s = s390_get_phb();
>> +
>> +    S390PCIBusDevice *pbdev, *next;
>> +
>> +    /* Trigger reset event for each passthrough ISM device currently in-use 
>> */
>> +    QTAILQ_FOREACH_SAFE(pbdev, &s->zpci_devs, link, next) {
>> +        if (pbdev->interp && pbdev->pft == ZPCI_PFT_ISM &&
>> +            pbdev->fh & FH_MASK_ENABLE) {
>> +            s390_pci_kvm_aif_disable(pbdev);
>> +
>> +            pci_device_reset(pbdev->pdev);
>> +        }
>> +    }
>> +}
> 
> 
> Could we instead define a VFIOPCIDevice::resetfn handler for these
> ISM devices (1014:04ed) ? This would be cleaner if possible.
> 
> If so, as a prerequisite, we would need to introduce in a little VFIO
> helper to define custom reset handlers.
> 
> Thanks,
> 
> C.
>

Oh interesting, I had not noticed that.  This may well work -- resetfn is 
currently setup via vfio_setup_resetfn_quirk but it would probably be easier to 
have a helper that takes the vdev and a function pointer so that we can provide 
a platform-specific reset handler (rather than having hw/vfio/pci-quirks.c 
worry about CONFIG_S390 etc).  I'll have to play around with this.