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

[Eric Farman]

On Fri, 2022-12-09 at 14:57 -0500, 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>

I realize Thomas already queued this, but for the record:

Reviewed-by: Eric Farman <farman@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;
>  }
>  
>  static bool get_host_fh(S390PCIBusDevice *pbdev, struct
> vfio_device_info *info,
> diff --git a/include/hw/s390x/s390-pci-bus.h b/include/hw/s390x/s390-
> pci-bus.h
> index 0605fcea24..4c812c65db 100644
> --- a/include/hw/s390x/s390-pci-bus.h
> +++ b/include/hw/s390x/s390-pci-bus.h
> @@ -39,6 +39,9 @@
>  #define UID_CHECKING_ENABLED 0x01
>  #define ZPCI_DTSM 0x40
>  
> +/* zPCI Function Types */
> +#define ZPCI_PFT_ISM 5
> +
>  OBJECT_DECLARE_SIMPLE_TYPE(S390pciState, S390_PCI_HOST_BRIDGE)
>  OBJECT_DECLARE_SIMPLE_TYPE(S390PCIBus, S390_PCI_BUS)
>  OBJECT_DECLARE_SIMPLE_TYPE(S390PCIBusDevice, S390_PCI_DEVICE)
> @@ -343,6 +346,7 @@ struct S390PCIBusDevice {
>      uint16_t noi;
>      uint16_t maxstbl;
>      uint8_t sum;
> +    uint8_t pft;
>      S390PCIGroup *pci_group;
>      ClpRspQueryPci zpci_fn;
>      S390MsixInfo msix;
> @@ -351,6 +355,7 @@ struct S390PCIBusDevice {
>      MemoryRegion msix_notify_mr;
>      IndAddr *summary_ind;
>      IndAddr *indicator;
> +    Notifier shutdown_notifier;
>      bool pci_unplug_request_processed;
>      bool unplug_requested;
>      bool interp;