Re: [PATCH] pci/pci_expander_bridge: migrate state of pxb/pxb-pcie devices.

[Vladimir Sementsov-Ogievskiy]

[add migration maintainers]

On 8/11/22 19:49, Andrey Ryabinin wrote:
> pxb/pxb-pcie/pxb-cxl devices currently doesn't have vmstate description
> So the state of device is not preserved during migration and
> guest can notice that as change of PCI_COMMAND_* registers state.
>
> The diff of lspci output before and after migration:
>
>   00:03.0 Host bridge [0600]: Red Hat, Inc. QEMU PCIe Expander bridge 
> [1b36:000b]
>           Subsystem: Red Hat, Inc QEMU PCIe Expander bridge [1af4:1100]
>   -       Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- 
> Stepping- SERR+ FastB2B- DisINTx-
>   +       Control: I/O- Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- 
> Stepping- SERR- FastB2B- DisINTx-
>           Status: Cap- 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort- <TAbort- 
> <MAbort- >SERR- <PERR- INTx-
>
> Add VMStateDescription to pxb devices so their state is transferred
> during migrations. For saving migration compatibility add
> 'x-config-reg-migration-enabled' property to pxb devices and disable
> it for all released machine types.
>
> Signed-off-by: Andrey Ryabinin <arbn@yandex-team.com>
> ---
>   hw/core/machine.c                   |  3 +++
>   hw/pci-bridge/pci_expander_bridge.c | 24 ++++++++++++++++++++++++
>   include/hw/pci/pci_bridge.h         |  1 +
>   3 files changed, 28 insertions(+)
>
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index a673302ccec..071853469e2 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -43,6 +43,9 @@
>   GlobalProperty hw_compat_7_0[] = {
>       { "arm-gicv3-common", "force-8-bit-prio", "on" },
>       { "nvme-ns", "eui64-default", "on"},
> +    { "pxb", "x-config-reg-migration-enabled", "off" },
> +    { "pxb-cxl", "x-config-reg-migration-enabled", "off" },
> +    { "pxb-pcie", "x-config-reg-migration-enabled", "off" },


Seems that it's too late for 7.1, rc2 is out and rc3 is coming soon. And that's 
not a degradation.

Up to maintainers, but I think we'd better start new hw_compat_7_1 for this 
thing.


>   };
>   const size_t hw_compat_7_0_len = G_N_ELEMENTS(hw_compat_7_0);
>   
> diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
> index c9e817aa586..a3680d4d045 100644
> --- a/hw/pci-bridge/pci_expander_bridge.c
> +++ b/hw/pci-bridge/pci_expander_bridge.c
> @@ -23,6 +23,7 @@
>   #include "qemu/error-report.h"
>   #include "qemu/module.h"
>   #include "sysemu/numa.h"
> +#include "migration/vmstate.h"
>   #include "hw/boards.h"
>   #include "qom/object.h"
>   
> @@ -404,9 +405,29 @@ static Property pxb_dev_properties[] = {
>       DEFINE_PROP_UINT8("bus_nr", PXBDev, bus_nr, 0),
>       DEFINE_PROP_UINT16("numa_node", PXBDev, numa_node, NUMA_NODE_UNASSIGNED),
>       DEFINE_PROP_BOOL("bypass_iommu", PXBDev, bypass_iommu, false),
> +    DEFINE_PROP_BOOL("x-config-reg-migration-enabled", PXBDev,
> +                     migratable, true),

With it, do we create a user-visible property? If so, is it possible to avoid 
it?

>       DEFINE_PROP_END_OF_LIST(),
>   };
>   
> +static bool pxb_vmstate_needed(void *opaque)
> +{
> +    PXBDev *pxb = opaque;
> +
> +    return pxb->migratable;
> +}
> +
> +static const VMStateDescription vmstate_pxb_device = {
> +    .name = "pxb-pci",
> +    .needed = pxb_vmstate_needed,
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_PCI_DEVICE(parent_obj, PXBDev),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
>   static void pxb_dev_class_init(ObjectClass *klass, void *data)
>   {
>       DeviceClass *dc = DEVICE_CLASS(klass);
> @@ -422,6 +443,7 @@ static void pxb_dev_class_init(ObjectClass *klass, void 
> *data)
>       device_class_set_props(dc, pxb_dev_properties);
>       dc->hotpluggable = false;
>       set_bit(DEVICE_CATEGORY_BRIDGE, dc->categories);
> +    dc->vmsd = &vmstate_pxb_device;
>   }
>   
>   static const TypeInfo pxb_dev_info = {
> @@ -460,6 +482,7 @@ static void pxb_pcie_dev_class_init(ObjectClass *klass, 
> void *data)
>       device_class_set_props(dc, pxb_dev_properties);
>       dc->hotpluggable = false;
>       set_bit(DEVICE_CATEGORY_BRIDGE, dc->categories);
> +    dc->vmsd = &vmstate_pxb_device;
>   }
>   
>   static const TypeInfo pxb_pcie_dev_info = {
> @@ -504,6 +527,7 @@ static void pxb_cxl_dev_class_init(ObjectClass *klass, void 
> *data)
>       /* Host bridges aren't hotpluggable. FIXME: spec reference */
>       dc->hotpluggable = false;
>       dc->reset = pxb_dev_reset;
> +    dc->vmsd = &vmstate_pxb_device;
>   }
>   
>   static const TypeInfo pxb_cxl_dev_info = {
> diff --git a/include/hw/pci/pci_bridge.h b/include/hw/pci/pci_bridge.h
> index ba4bafac7c2..404dc02e36e 100644
> --- a/include/hw/pci/pci_bridge.h
> +++ b/include/hw/pci/pci_bridge.h
> @@ -91,6 +91,7 @@ struct PXBDev {
>       uint8_t bus_nr;
>       uint16_t numa_node;
>       bool bypass_iommu;
> +    bool migratable;
>       struct cxl_dev {
>           CXLHost *cxl_host_bridge; /* Pointer to a CXLHost */
>       } cxl;


--
Best regards,
Vladimir