* Peter Xu (pet...@redhat.com) wrote:
> In the past, we prioritized IOMMU migration so that we have such a
> priority order:
>
> IOMMU > PCI Devices
>
> When migrating a guest with both vIOMMU and pcie-root-port, we'll always
> migrate vIOMMU first, since pcie-root-port will be seen to have the same
> priority of general PCI devices.
>
> That's problematic.
>
> The thing is that PCI bus number information is stored in the root port,
> and that is needed by vIOMMU during post_load(), e.g., to figure out
> context entry for a device. If we don't have correct bus numbers for
> devices, we won't be able to recover device state of the DMAR memory
> regions, and things will be messed up.
>
> So let's boost the PCIe root ports to be even with higher priority:
>
> PCIe Root Port > IOMMU > PCI Devices
>
> A smoke test shows that this patch fixes bug 1538953.
Two questions (partially overlapping with what I replied to Michaels):
a) What happens with multiple IOMMUs?
b) What happens with multiple root ports?
c) How correct is this ordering on different implementations
(e.g. ARM/Power/etc)
Dave
>
> CC: Alex Williamson <alex.william...@redhat.com>
> CC: Marcel Apfelbaum <mar...@redhat.com>
> CC: Michael S. Tsirkin <m...@redhat.com>
> CC: Dr. David Alan Gilbert <dgilb...@redhat.com>
> CC: Juan Quintela <quint...@redhat.com>
> CC: Laurent Vivier <lviv...@redhat.com>
> Bug: https://bugzilla.redhat.com/show_bug.cgi?id=1538953
> Reported-by: Maxime Coquelin <maxime.coque...@redhat.com>
> Signed-off-by: Peter Xu <pet...@redhat.com>
> ---
> Marcel & all,
>
> I think it's possible that we need similar thing for other bridge-like
> devices, but I'm not that familiar. Would you help confirm? Thanks,
> ---
> hw/pci-bridge/gen_pcie_root_port.c | 1 +
> include/migration/vmstate.h | 1 +
> 2 files changed, 2 insertions(+)
>
> diff --git a/hw/pci-bridge/gen_pcie_root_port.c
> b/hw/pci-bridge/gen_pcie_root_port.c
> index 0e2f2e8bf1..e6ff1effd8 100644
> --- a/hw/pci-bridge/gen_pcie_root_port.c
> +++ b/hw/pci-bridge/gen_pcie_root_port.c
> @@ -101,6 +101,7 @@ static void gen_rp_realize(DeviceState *dev, Error **errp)
>
> static const VMStateDescription vmstate_rp_dev = {
> .name = "pcie-root-port",
> + .priority = MIG_PRI_PCIE_ROOT_PORT,
> .version_id = 1,
> .minimum_version_id = 1,
> .post_load = pcie_cap_slot_post_load,
> diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
> index 8c3889433c..491449db9f 100644
> --- a/include/migration/vmstate.h
> +++ b/include/migration/vmstate.h
> @@ -148,6 +148,7 @@ enum VMStateFlags {
> typedef enum {
> MIG_PRI_DEFAULT = 0,
> MIG_PRI_IOMMU, /* Must happen before PCI devices */
> + MIG_PRI_PCIE_ROOT_PORT, /* Must happen before IOMMU */
> MIG_PRI_GICV3_ITS, /* Must happen before PCI devices */
> MIG_PRI_GICV3, /* Must happen before the ITS */
> MIG_PRI_MAX,
> --
> 2.14.3
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
