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Re: [PATCH v5 04/14] vpci: cancel pending map/unmap on vpci removal
- To: Oleksandr Andrushchenko <andr2000@xxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 12 Jan 2022 16:27:30 +0100
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- Cc: julien@xxxxxxx, sstabellini@xxxxxxxxxx, oleksandr_tyshchenko@xxxxxxxx, volodymyr_babchuk@xxxxxxxx, Artem_Mygaiev@xxxxxxxx, roger.pau@xxxxxxxxxx, andrew.cooper3@xxxxxxxxxx, george.dunlap@xxxxxxxxxx, paul@xxxxxxx, bertrand.marquis@xxxxxxx, rahul.singh@xxxxxxx, Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Wed, 12 Jan 2022 15:27:45 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 25.11.2021 12:02, Oleksandr Andrushchenko wrote:
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
>
> When a vPCI is removed for a PCI device it is possible that we have
> scheduled a delayed work for map/unmap operations for that device.
> For example, the following scenario can illustrate the problem:
>
> pci_physdev_op
> pci_add_device
> init_bars -> modify_bars -> defer_map ->
> raise_softirq(SCHEDULE_SOFTIRQ)
> iommu_add_device <- FAILS
> vpci_remove_device -> xfree(pdev->vpci)
>
> leave_hypervisor_to_guest
> vpci_process_pending: v->vpci.mem != NULL; v->vpci.pdev->vpci == NULL
>
> For the hardware domain we continue execution as the worse that
> could happen is that MMIO mappings are left in place when the
> device has been deassigned.
>
> For unprivileged domains that get a failure in the middle of a vPCI
> {un}map operation we need to destroy them, as we don't know in which
> state the p2m is. This can only happen in vpci_process_pending for
> DomUs as they won't be allowed to call pci_add_device.
>
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
>
> ---
> Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
> Since v4:
> - crash guest domain if map/unmap operation didn't succeed
> - re-work vpci cancel work to cancel work on all vCPUs
> - use new locking scheme with pdev->vpci_lock
> New in v4
>
> Fixes: 86dbcf6e30cb ("vpci: cancel pending map/unmap on vpci removal")
What is this about?
Jan
|
