On Fri, 18 Oct 2019 at 16:07, Damien Hedde <damien.he...@greensocs.com> wrote:
>
> In qdev_set_parent_bus(), when changing the parent bus of a
> realized device, if the source and destination buses are not in the
> same reset state, some adaptation are required. This patch adds
"adaptations"
> needed call to resettable_change_parent() to make sure a device reset
> state stays coherent with its parent bus.
>
> The addition is a no-op if:
> 1. the device being parented is not realized.
> 2. the device is realized, but both buses are not under reset.
>
> Case 2 means that as long as qdev_set_parent_bus() is called
> during the machine realization procedure (which is before the
> machine reset so nothing is in reset), it is a no op.
>
> There are 49 call sites of qdev_set_parent_bus(). All but one fall
> into the no-op case:
> + 28 calls related to virtio (in hw/{s390x,display,virtio}/
> {vhost,virtio}-xxx.c) to set a _vdev_/_vgpu_ composing device
> parent bus just before realizing the _vdev_/_vgpu_.
> + hw/qdev.c: when creating a device in qdev_try_create()
> + hw/sysbus.c: when initializing a device in the sysbus
> + hw/display/virtio-gpu-pci.c: before realizing VirtIOGPUPCIBase/vgpu
> + hw/display/virtio-vga.c: before realizing VirtIOVGABase/vgpu
> + hw/i386/amd_iommu.c: before realizing AMDVIState/pci
> + hw/misc/auxbus.c: when creating an AUXBus
> + hw/misc/auxbus.c: when creating an AUXBus child
> + hw/misc/macio/macio.c: when initializing a MACIOState child
> + hw/misc/macio/macio.c: before realizing NewWorldMacIOState/pmu
> + hw/misc/macio/macio.c: before realizing NewWorldMacIOState/cuda
> + hw/pci-host/designware.c: before realizing DesignwarePCIEHost/root
> + hw/pci-host/gpex.c: before realizing GPEXHost/root
> + hw/pci-host/prep.c: when initializaing PREPPCIState/pci_dev
> + hw/pci-host/q35.c: before realizing Q35PCIHost/mch
> + hw/pci-host/versatile.c: when initializing PCIVPBState/pci_dev
> + hw/pci-host/xilinx-pcie.c: before realizing XilinxPCIEHost/root
> + hw/s390x/event-facility.c: when creating SCLPEventFacility/
> TYPE_SCLP_QUIESCE
> + hw/s390x/event-facility.c: ditto with SCLPEventFacility/
> TYPE_SCLP_CPU_HOTPLUG
> + hw/s390x/sclp.c: Not trivial because it is called on a SLCPDevice
> just after realizing it. Ok because at this point the destination
> bus (sysbus) is not in reset; the realize step is before the
> machine reset.
> + hw/sd/core.c: Not OK. Used in sdbus_reparent_card(). See below.
> + hw/ssi/ssi.c: Used to put spi slave on spi bus and connect the cs
> line in ssi_auto_connect_slave(). Ok because this function is only
> used in realize step in hw/ssi/aspeed_smc.ci, hw/ssi/imx_spi.c,
> hw/ssi/mss-spi.c, hw/ssi/xilinx_spi.c and hw/ssi/xilinx_spips.c.
> + hw/xen/xen-legacy-backend.c: when creating a XenLegacyDevice device
> + qdev-monitor.c: in device hotplug creation procedure before realize
This is a really useful analysis to have in the commit message;
thanks!
(Side note: I wonder if the sclp.c case could be reordered so
it realizes the device after parenting it? Anyway, not something
to worry about now.)
> Note that this commit alone will have no effect, right now there is no
> use of resettable API to reset anything. So a bus will never be tagged
> as in-reset by this same API.
>
> The one place where side-effect will occurs is in hw/sd/core.c in
> sdbus_reparent_card(). This function is only used in the raspi machines,
> including during the sysbus reset procedure. This case will be fixed by
> a following commit before globally enabling resettable API for sysbus
> reset.
>
> Signed-off-by: Damien Hedde <damien.he...@greensocs.com>
Reviewed-by: Peter Maydell <peter.mayd...@linaro.org>
thanks
-- PMM
