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

[Thomas Huth <thuth@redhat.com>]

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.

  Thomas