Re: [PATCH] s390x/pci: reset ISM passthrough devices on shutdown and system reset

[Matthew Rosato]

On 12/12/22 6:34 AM, Thomas Huth wrote:
> On 09/12/2022 20.57, Matthew Rosato wrote:
>> ISM device firmware stores unique state information that can
>> can cause a wholesale unmap of the associated IOMMU (e.g. when
>> we get a termination signal for QEMU) to trigger firmware errors
>> because firmware believes we are attempting to invalidate entries
>> that are still in-use by the guest OS (when in fact that guest is
>> in the process of being terminated or rebooted).
>> To alleviate this, register both a shutdown notifier (for unexpected
>> termination cases e.g. virsh destroy) as well as a reset callback
>> (for cases like guest OS reboot).  For each of these scenarios, trigger
>> PCI device reset; this is enough to indicate to firmware that the IOMMU
>> is no longer in-use by the guest OS, making it safe to invalidate any
>> associated IOMMU entries.
>>
>> Fixes: 15d0e7942d3b ("s390x/pci: don't fence interpreted devices without 
>> MSI-X")
>> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
>> ---
>>   hw/s390x/s390-pci-bus.c         | 28 ++++++++++++++++++++++++++++
>>   hw/s390x/s390-pci-vfio.c        |  2 ++
>>   include/hw/s390x/s390-pci-bus.h |  5 +++++
>>   3 files changed, 35 insertions(+)
>>
>> diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
>> index 977e7daa15..02751f3597 100644
>> --- a/hw/s390x/s390-pci-bus.c
>> +++ b/hw/s390x/s390-pci-bus.c
>> @@ -24,6 +24,8 @@
>>   #include "hw/pci/msi.h"
>>   #include "qemu/error-report.h"
>>   #include "qemu/module.h"
>> +#include "sysemu/reset.h"
>> +#include "sysemu/runstate.h"
>>     #ifndef DEBUG_S390PCI_BUS
>>   #define DEBUG_S390PCI_BUS  0
>> @@ -150,10 +152,30 @@ out:
>>       psccb->header.response_code = cpu_to_be16(rc);
>>   }
>>   +static void s390_pci_shutdown_notifier(Notifier *n, void *opaque)
>> +{
>> +    S390PCIBusDevice *pbdev = container_of(n, S390PCIBusDevice,
>> +                                           shutdown_notifier);
>> +
>> +    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 */
>>       if (pbdev->pdev) {
>>           DeviceState *pdev = DEVICE(pbdev->pdev);
>> @@ -1111,6 +1133,12 @@ static void s390_pcihost_plug(HotplugHandler 
>> *hotplug_dev, DeviceState *dev,
>>                   pbdev->fh |= FH_SHM_VFIO;
>>                   pbdev->forwarding_assist = false;
>>               }
>> +            /* Register shutdown notifier and reset callback for ISM 
>> devices */
>> +            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;
>>               /* Always intercept emulated devices */
>> diff --git a/hw/s390x/s390-pci-vfio.c b/hw/s390x/s390-pci-vfio.c
>> index 5f0adb0b4a..419763f829 100644
>> --- a/hw/s390x/s390-pci-vfio.c
>> +++ b/hw/s390x/s390-pci-vfio.c
>> @@ -122,6 +122,8 @@ static void s390_pci_read_base(S390PCIBusDevice *pbdev,
>>       /* The following values remain 0 until we support other FMB formats */
>>       pbdev->zpci_fn.fmbl = 0;
>>       pbdev->zpci_fn.pft = 0;
>> +    /* Store function type separately for type-specific behavior */
>> +    pbdev->pft = cap->pft;
>>   }
> 
> Thanks, queued:
> 
>  https://gitlab.com/thuth/qemu/-/commits/s390x-next/
> 
> I had to adjust the hunk in s390_pci_read_base() due to a conflict with your 
> earlier patch, please check whether it looks sane to you.

Yep, that adjustment is good (and FWIW, was the same on my local branch).  
Thanks!

Matt