On Fri, Mar 18, 2022 at 08:18:19PM +0100, Lukasz Maniak wrote:
> From: Łukasz Gieryk <lukasz.gieryk@linux.intel.com>
>
> PCI device capable of SR-IOV support is a new, still-experimental
> feature with only a single working example of the Nvme device.
>
> This patch in an attempt to fix a double-free problem when a
> SR-IOV-capable Nvme device is hot-unplugged. The problem and the
> reproduction steps can be found in this thread:
>
> https://patchew.org/QEMU/20220217174504.1051716-1-lukasz.maniak@linux.intel.com/20220217174504.1051716-14-lukasz.maniak@linux.intel.com/
>
> Details of the proposed solution are, for convenience, included below.
>
> 1) The current SR-IOV implementation assumes it’s the PhysicalFunction
> that creates and deletes VirtualFunctions.
> 2) It’s a design decision (the Nvme device at least) for the VFs to be
> of the same class as PF. Effectively, they share the dc->hotpluggable
> value.
> 3) When a VF is created, it’s added as a child node to PF’s PCI bus
> slot.
> 4) Monitor/device_del triggers the ACPI mechanism. The implementation is
> not aware of SR/IOV and ejects PF’s PCI slot, directly unrealizing all
> hot-pluggable (!acpi_pcihp_pc_no_hotplug) children nodes.
> 5) VFs are unrealized directly, and it doesn’t work well with (1).
> SR/IOV structures are not updated, so when it’s PF’s turn to be
> unrealized, it works on stale pointers to already-deleted VFs.
>
> Signed-off-by: Łukasz Gieryk <lukasz.gieryk@linux.intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
feel free to include when merging the rest of the patchset.
> ---
> hw/acpi/pcihp.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c
> index 6351bd3424d..248839e1110 100644
> --- a/hw/acpi/pcihp.c
> +++ b/hw/acpi/pcihp.c
> @@ -192,8 +192,12 @@ static bool acpi_pcihp_pc_no_hotplug(AcpiPciHpState *s, PCIDevice *dev)
> * ACPI doesn't allow hotplug of bridge devices. Don't allow
> * hot-unplug of bridge devices unless they were added by hotplug
> * (and so, not described by acpi).
> + *
> + * Don't allow hot-unplug of SR-IOV Virtual Functions, as they
> + * will be removed implicitly, when Physical Function is unplugged.
> */
> - return (pc->is_bridge && !dev->qdev.hotplugged) || !dc->hotpluggable;
> + return (pc->is_bridge && !dev->qdev.hotplugged) || !dc->hotpluggable ||
> + pci_is_vf(dev);
> }
>
> static void acpi_pcihp_eject_slot(AcpiPciHpState *s, unsigned bsel, unsigned slots)
> --
> 2.25.1