Re: [PATCH] hw/pci-host: save/restore pci host config register

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Jul 23, 2020 at 06:49:35PM +0800, Wang King wrote:
> From: Hogan Wang <king.wang@huawei.com>
> 
> The pci host config register is used to save PCI address for
> read/write config data. If guest write a value to config register,
> and then pause the vcpu to migrate, After the migration, the guest
> continue to write pci config data, and the write data will be ignored
> because of new qemu process lost the config register state.

Wow I can't believe we have such a bug after so many years.
Question is, this will break cross-version migration if we just add it.
Could we use some trick so people can upgrade in the field
without breaking migration?

I regret we still don't have an extensible format where we could
add fields without breaking everything ...
CC Julua, Dgilbert to take a look.

> Example:
> 1. guest booting in seabios.
> 2. guest enabled the SMM memory window in piix4_apmc_smm_setup, and
> then try to close the SMM memory window.
> 3. pasued vcpu to finish migration.
> 4. guest close the SMM memory window fail becasue of config register
> state lost.
> 5. guest continue to boot and crash in ipxe option ROM (SMM memory
> window is enabled).
> 
> Due to the complex guest, the negative effect is unpredictable.

Could we get a sign-off please?

The sign-off is a simple line at the end of the explanation for the
patch, which certifies that you wrote it or otherwise have the right to
pass it on as an open-source patch.  The rules are pretty simple: if you
can certify the below:

Developer's Certificate of Origin 1.1
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

By making a contribution to this project, I certify that:

        (a) The contribution was created in whole or in part by me and I
            have the right to submit it under the open source license
            indicated in the file; or

        (b) The contribution is based upon previous work that, to the best
            of my knowledge, is covered under an appropriate open source
            license and I have the right under that license to submit that
            work with modifications, whether created in whole or in part
            by me, under the same open source license (unless I am
            permitted to submit under a different license), as indicated
            in the file; or

        (c) The contribution was provided directly to me by some other
            person who certified (a), (b) or (c) and I have not modified
            it.

        (d) I understand and agree that this project and the contribution
            are public and that a record of the contribution (including all
            personal information I submit with it, including my sign-off) is
            maintained indefinitely and may be redistributed consistent with
            this project or the open source license(s) involved.

then you just add a line saying::

        Signed-off-by: Random J Developer <random@developer.example.org>

using your real name (sorry, no pseudonyms or anonymous contributions.)
           

> ---
>  hw/pci-host/i440fx.c       | 11 +++++++++++
>  hw/pci-host/q35.c          | 11 +++++++++++
>  hw/pci/pci_host.c          | 11 +++++++++++
>  hw/pci/pcie_host.c         | 11 +++++++++++
>  include/hw/pci/pci_host.h  | 10 ++++++++++
>  include/hw/pci/pcie_host.h | 10 ++++++++++
>  6 files changed, 64 insertions(+)
> 
> diff --git a/hw/pci-host/i440fx.c b/hw/pci-host/i440fx.c
> index 8ed2417f0c..17705bb025 100644
> --- a/hw/pci-host/i440fx.c
> +++ b/hw/pci-host/i440fx.c
> @@ -118,6 +118,16 @@ static const VMStateDescription vmstate_i440fx = {
>      }
>  };
>  
> +static const VMStateDescription vmstate_i440fx_pcihost = {
> +    .name = "I440FX_PCIHost",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_PCI_HOST(parent_obj, I440FXState),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
>  static void i440fx_pcihost_get_pci_hole_start(Object *obj, Visitor *v,
>                                                const char *name, void *opaque,
>                                                Error **errp)
> @@ -398,6 +408,7 @@ static void i440fx_pcihost_class_init(ObjectClass *klass, void *data)
>      hc->root_bus_path = i440fx_pcihost_root_bus_path;
>      dc->realize = i440fx_pcihost_realize;
>      dc->fw_name = "pci";
> +    dc->vmsd = &vmstate_i440fx_pcihost;
>      device_class_set_props(dc, i440fx_props);
>      /* Reason: needs to be wired up by pc_init1 */
>      dc->user_creatable = false;
> diff --git a/hw/pci-host/q35.c b/hw/pci-host/q35.c
> index b67cb9c29f..5e323be2e3 100644
> --- a/hw/pci-host/q35.c
> +++ b/hw/pci-host/q35.c
> @@ -165,6 +165,16 @@ static void q35_host_get_pci_hole64_end(Object *obj, Visitor *v,
>      visit_type_uint64(v, name, &value, errp);
>  }
>  
> +static const VMStateDescription vmstate_q35_pcihost = {
> +    .name = "Q35_PCIHost",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_PCIE_HOST(parent_obj, Q35PCIHost),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
>  /*
>   * NOTE: setting defaults for the mch.* fields in this table
>   * doesn't work, because mch is a separate QOM object that is
> @@ -194,6 +204,7 @@ static void q35_host_class_init(ObjectClass *klass, void *data)
>  
>      hc->root_bus_path = q35_host_root_bus_path;
>      dc->realize = q35_host_realize;
> +    dc->vmsd = &vmstate_q35_pcihost;
>      device_class_set_props(dc, q35_host_props);
>      /* Reason: needs to be wired up by pc_q35_init */
>      dc->user_creatable = false;
> diff --git a/hw/pci/pci_host.c b/hw/pci/pci_host.c
> index ce7bcdb1d5..7cdd5a3ea3 100644
> --- a/hw/pci/pci_host.c
> +++ b/hw/pci/pci_host.c
> @@ -24,6 +24,7 @@
>  #include "hw/pci/pci_host.h"
>  #include "qemu/module.h"
>  #include "hw/pci/pci_bus.h"
> +#include "migration/vmstate.h"
>  #include "trace.h"
>  
>  /* debug PCI */
> @@ -200,6 +201,16 @@ const MemoryRegionOps pci_host_data_be_ops = {
>      .endianness = DEVICE_BIG_ENDIAN,
>  };
>  
> +const VMStateDescription vmstate_pcihost = {
> +    .name = "PCIHost",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_UINT32(config_reg, PCIHostState),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
>  static const TypeInfo pci_host_type_info = {
>      .name = TYPE_PCI_HOST_BRIDGE,
>      .parent = TYPE_SYS_BUS_DEVICE,
> diff --git a/hw/pci/pcie_host.c b/hw/pci/pcie_host.c
> index 3534006f99..a653c39bb7 100644
> --- a/hw/pci/pcie_host.c
> +++ b/hw/pci/pcie_host.c
> @@ -24,6 +24,7 @@
>  #include "hw/pci/pcie_host.h"
>  #include "qemu/module.h"
>  #include "exec/address-spaces.h"
> +#include "migration/vmstate.h"
>  
>  /* a helper function to get a PCIDevice for a given mmconfig address */
>  static inline PCIDevice *pcie_dev_find_by_mmcfg_addr(PCIBus *s,
> @@ -121,6 +122,16 @@ void pcie_host_mmcfg_update(PCIExpressHost *e,
>      memory_region_transaction_commit();
>  }
>  
> +const VMStateDescription vmstate_pciehost = {
> +    .name = "PCIEHost",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_PCI_HOST(pci, PCIExpressHost),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
>  static const TypeInfo pcie_host_type_info = {
>      .name = TYPE_PCIE_HOST_BRIDGE,
>      .parent = TYPE_PCI_HOST_BRIDGE,
> diff --git a/include/hw/pci/pci_host.h b/include/hw/pci/pci_host.h
> index 9ce088bd13..fc88305e04 100644
> --- a/include/hw/pci/pci_host.h
> +++ b/include/hw/pci/pci_host.h
> @@ -70,4 +70,14 @@ extern const MemoryRegionOps pci_host_conf_be_ops;
>  extern const MemoryRegionOps pci_host_data_le_ops;
>  extern const MemoryRegionOps pci_host_data_be_ops;
>  
> +extern const VMStateDescription vmstate_pcihost;
> +
> +#define VMSTATE_PCI_HOST(_field, _state) {                           \
> +    .name       = (stringify(_field)),                               \
> +    .size       = sizeof(PCIHostState),                              \
> +    .vmsd       = &vmstate_pcihost,                                  \
> +    .flags      = VMS_STRUCT,                                        \
> +    .offset     = vmstate_offset_value(_state, _field, PCIHostState),\
> +}
> +
>  #endif /* PCI_HOST_H */
> diff --git a/include/hw/pci/pcie_host.h b/include/hw/pci/pcie_host.h
> index 3f7b9886d1..a91ba0241a 100644
> --- a/include/hw/pci/pcie_host.h
> +++ b/include/hw/pci/pcie_host.h
> @@ -78,4 +78,14 @@ void pcie_host_mmcfg_update(PCIExpressHost *e,
>                                           PCIE_MMCFG_DEVFN_MASK)
>  #define PCIE_MMCFG_CONFOFFSET(addr)     ((addr) & PCIE_MMCFG_CONFOFFSET_MASK)
>  
> +extern const VMStateDescription vmstate_pciehost;
> +
> +#define VMSTATE_PCIE_HOST(_field, _state) {                            \
> +    .name       = (stringify(_field)),                                 \
> +    .size       = sizeof(PCIExpressHost),                              \
> +    .vmsd       = &vmstate_pcihost,                                    \
> +    .flags      = VMS_STRUCT,                                          \
> +    .offset     = vmstate_offset_value(_state, _field, PCIExpressHost),\
> +}
> +
>  #endif /* PCIE_HOST_H */
> -- 
> 2.23.0
>