linux-kernel - Re: [PATCH v1 0/6] Error recovery for vfio-pci devices on s390x

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Message-ID: <5ca8d085-c211-4b94-a74a-94e75e10d47e@linux.ibm.com>
Date: Wed, 13 Aug 2025 10:45:55 -0700
From: Farhan Ali <alifm@...ux.ibm.com>
To: linux-s390@...r.kernel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc: schnelle@...ux.ibm.com, mjrosato@...ux.ibm.com, alex.williamson@...hat.com
Subject: Re: [PATCH v1 0/6] Error recovery for vfio-pci devices on s390x

Also posted a QEMU series utilizing these kernel patches
https://lore.kernel.org/qemu-devel/20250813174152.1238-1-alifm@linux.ibm.com/

Thanks
Farhan

On 8/13/2025 10:08 AM, Farhan Ali wrote:
> Hi,
>
> This Linux kernel patch series introduces support for error recovery for
> passthrough PCI devices on System Z (s390x).
>
> Background
> ----------
> For PCI devices on s390x an operating system receives platform specific
> error events from firmware rather than through AER.Today for
> passthrough/userspace devices, we don't attempt any error recovery
> and ignore any error events for the devices. The passthrough/userspace devices are
> managed by the vfio-pci driver. The driver does register error handling
> callbacks (error_detected), and on an error trigger an eventfd to userspace.
> But we need a mechanism to notify userspace (QEMU/guest/userspace drivers) about
> the error event.
>
> Proposal
> --------
> We can expose this error information (currently only the PCI Error Code) via a
> device specific memory region for s390 vfio pci devices. Userspace can then read
> the memory region to obtain the error information and take appropriate actions
> such as driving a device reset. The memory region provides some flexibility in
> providing more information in the future if required.
>
> I would appreciate some feedback on this approach.
>
> Thanks
> Farhan
>
> Farhan Ali (6):
>    s390/pci: Restore airq unconditionally for the zPCI device
>    s390/pci: Update the logic for detecting passthrough device
>    s390/pci: Store PCI error information for passthrough devices
>    vfio-pci/zdev: Setup a zpci memory region for error information
>    vfio-pci/zdev: Perform platform specific function reset for zPCI
>    vfio: Allow error notification and recovery for ISM device
>
>   arch/s390/include/asm/pci.h       |  29 +++++++
>   arch/s390/pci/pci.c               |   2 +
>   arch/s390/pci/pci_event.c         | 107 ++++++++++++++-----------
>   arch/s390/pci/pci_irq.c           |   3 +-
>   drivers/vfio/pci/vfio_pci_core.c  |  22 +++++-
>   drivers/vfio/pci/vfio_pci_intrs.c |   2 +-
>   drivers/vfio/pci/vfio_pci_priv.h  |   8 ++
>   drivers/vfio/pci/vfio_pci_zdev.c  | 126 +++++++++++++++++++++++++++++-
>   include/uapi/linux/vfio.h         |   2 +
>   include/uapi/linux/vfio_zdev.h    |   5 ++
>   10 files changed, 253 insertions(+), 53 deletions(-)
>