Re: [Qemu-devel] [PATCH v3] virtio-pci: fix migration for pci bus master

[Greg Kurz <gkurz@linux.vnet.ibm.com>]

On Mon, 20 Oct 2014 09:58:50 +0300
"Michael S. Tsirkin" <mst@redhat.com> wrote:
> Current support for bus master (clearing OK bit) together with the need to
> support guests which do not enable PCI bus mastering, leads to extra state in
> VIRTIO_PCI_FLAG_BUS_MASTER_BUG bit, which isn't robust in case of cross-version
> migration for the case when guests use the device before setting DRIVER_OK.
> 
> Rip out this code, and replace it:
> -   Modern QEMU doesn't need VIRTIO_PCI_FLAG_BUS_MASTER_BUG
>     so just drop it for latest machine type.
> -   For compat machine types, set PCI_COMMAND if DRIVER_OK
>     is set.
> 
> As this is needed for 2.1 for both pc and ppc, move PC_COMPAT macros from pc.h
> to a new common header.
> 
> Reviewed-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
> Tested-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
> 
> Alexander, could you pls ack me merging this?
> Thanks!
> 

This patch conflicts with the following commit in Alex's ppc-next branch:

commit 6dd65a940532eaac42a302c30964b0d42967e187
Author: David Gibson <david@gibson.dropbear.id.au>
Date:   Mon Sep 8 15:30:31 2014 +1000

    spapr: Cleanup machine naming conventions, and prepare for 2.2 release

Easy to fix though.

Alex,

I can send the rebased version if you want.

Cheers.

--
Greg

> 
> changes from v2:
>     drop default = -1 from ppc - was a typo, reported by Greg
> 
>  hw/virtio/virtio-pci.h |  5 +++++
>  include/hw/compat.h    | 16 ++++++++++++++++
>  include/hw/i386/pc.h   | 10 ++--------
>  hw/i386/pc_piix.c      |  2 +-
>  hw/i386/pc_q35.c       |  2 +-
>  hw/ppc/spapr.c         |  7 +++++++
>  hw/virtio/virtio-pci.c | 29 +++++++++++------------------
>  7 files changed, 43 insertions(+), 28 deletions(-)
>  create mode 100644 include/hw/compat.h
> 
> diff --git a/hw/virtio/virtio-pci.h b/hw/virtio/virtio-pci.h
> index 1cea157..8873b6d 100644
> --- a/hw/virtio/virtio-pci.h
> +++ b/hw/virtio/virtio-pci.h
> @@ -53,6 +53,11 @@ typedef struct VirtioBusClass VirtioPCIBusClass;
>  #define VIRTIO_PCI_BUS_CLASS(klass) \
>          OBJECT_CLASS_CHECK(VirtioPCIBusClass, klass, TYPE_VIRTIO_PCI_BUS)
> 
> +/* Need to activate work-arounds for buggy guests at vmstate load. */
> +#define VIRTIO_PCI_FLAG_BUS_MASTER_BUG_MIGRATION_BIT  0
> +#define VIRTIO_PCI_FLAG_BUS_MASTER_BUG_MIGRATION \
> +    (1 << VIRTIO_PCI_FLAG_BUS_MASTER_BUG_MIGRATION_BIT)
> +
>  /* Performance improves when virtqueue kick processing is decoupled from the
>   * vcpu thread using ioeventfd for some devices. */
>  #define VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT 1
> diff --git a/include/hw/compat.h b/include/hw/compat.h
> new file mode 100644
> index 0000000..47f6ff5
> --- /dev/null
> +++ b/include/hw/compat.h
> @@ -0,0 +1,16 @@
> +#ifndef HW_COMPAT_H
> +#define HW_COMPAT_H
> +
> +#define HW_COMPAT_2_1 \
> +        {\
> +            .driver   = "intel-hda",\
> +            .property = "old_msi_addr",\
> +            .value    = "on",\
> +        },\
> +        {\
> +            .driver   = "virtio-pci",\
> +            .property = "virtio-pci-bus-master-bug-migration",\
> +            .value    = "on",\
> +        }
> +
> +#endif /* HW_COMPAT_H */
> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> index bae023a..82ad046 100644
> --- a/include/hw/i386/pc.h
> +++ b/include/hw/i386/pc.h
> @@ -14,6 +14,7 @@
>  #include "sysemu/sysemu.h"
>  #include "hw/pci/pci.h"
>  #include "hw/boards.h"
> +#include "hw/compat.h"
> 
>  #define HPET_INTCAP "hpet-intcap"
> 
> @@ -307,15 +308,8 @@ int e820_add_entry(uint64_t, uint64_t, uint32_t);
>  int e820_get_num_entries(void);
>  bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);
> 
> -#define PC_COMPAT_2_1 \
> -        {\
> -            .driver   = "intel-hda",\
> -            .property = "old_msi_addr",\
> -            .value    = "on",\
> -        }
> -
>  #define PC_COMPAT_2_0 \
> -        PC_COMPAT_2_1, \
> +        HW_COMPAT_2_1, \
>          {\
>              .driver   = "virtio-scsi-pci",\
>              .property = "any_layout",\
> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> index 553afdd..a1634ab 100644
> --- a/hw/i386/pc_piix.c
> +++ b/hw/i386/pc_piix.c
> @@ -502,7 +502,7 @@ static QEMUMachine pc_i440fx_machine_v2_1 = {
>      .name = "pc-i440fx-2.1",
>      .init = pc_init_pci,
>      .compat_props = (GlobalProperty[]) {
> -        PC_COMPAT_2_1,
> +        HW_COMPAT_2_1,
>          { /* end of list */ }
>      },
>  };
> diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
> index a199043..f330f7a 100644
> --- a/hw/i386/pc_q35.c
> +++ b/hw/i386/pc_q35.c
> @@ -365,7 +365,7 @@ static QEMUMachine pc_q35_machine_v2_1 = {
>      .name = "pc-q35-2.1",
>      .init = pc_q35_init,
>      .compat_props = (GlobalProperty[]) {
> -        PC_COMPAT_2_1,
> +        HW_COMPAT_2_1,
>          { /* end of list */ }
>      },
>  };
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 2becc9f..623f626 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -57,6 +57,8 @@
>  #include "trace.h"
>  #include "hw/nmi.h"
> 
> +#include "hw/compat.h"
> +
>  #include <libfdt.h>
> 
>  /* SLOF memory layout:
> @@ -1689,10 +1691,15 @@ static const TypeInfo spapr_machine_info = {
>  static void spapr_machine_2_1_class_init(ObjectClass *oc, void *data)
>  {
>      MachineClass *mc = MACHINE_CLASS(oc);
> +    static GlobalProperty compat_props[] = {
> +        HW_COMPAT_2_1,
> +        { /* end of list */ }1
> +    };
> 
>      mc->name = "pseries-2.1";
>      mc->desc = "pSeries Logical Partition (PAPR compliant) v2.1";
>      mc->is_default = 0;
> +    mc->compat_props = compat_props;
>  }
> 
>  static const TypeInfo spapr_machine_2_1_info = {
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index a827cd4..a499a3c 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -86,9 +86,6 @@
>   * 12 is historical, and due to x86 page size. */
>  #define VIRTIO_PCI_QUEUE_ADDR_SHIFT    12
> 
> -/* Flags track per-device state like workarounds for quirks in older guests. */
> -#define VIRTIO_PCI_FLAG_BUS_MASTER_BUG  (1 << 0)
> -
>  static void virtio_pci_bus_new(VirtioBusState *bus, size_t bus_size,
>                                 VirtIOPCIProxy *dev);
> 
> @@ -323,14 +320,6 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
>                                       proxy->pci_dev.config[PCI_COMMAND] |
>                                       PCI_COMMAND_MASTER, 1);
>          }
> -
> -        /* Linux before 2.6.34 sets the device as OK without enabling
> -           the PCI device bus master bit. In this case we need to disable
> -           some safety checks. */
> -        if ((val & VIRTIO_CONFIG_S_DRIVER_OK) &&
> -            !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
> -            proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG;
> -        }
>          break;
>      case VIRTIO_MSI_CONFIG_VECTOR:
>          msix_vector_unuse(&proxy->pci_dev, vdev->config_vector);
> @@ -483,8 +472,7 @@ static void virtio_write_config(PCIDevice *pci_dev, uint32_t address,
>      pci_default_write_config(pci_dev, address, val, len);
> 
>      if (range_covers_byte(address, len, PCI_COMMAND) &&
> -        !(pci_dev->config[PCI_COMMAND] & PCI_COMMAND_MASTER) &&1
> -        !(proxy->flags & VIRTIO_PCI_FLAG_BUS_MASTER_BUG)) {
> +        !(pci_dev->config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
>          virtio_pci_stop_ioeventfd(proxy);
>          virtio_set_status(vdev, vdev->status & ~VIRTIO_CONFIG_S_DRIVER_OK);
>      }
> @@ -895,11 +883,15 @@ static void virtio_pci_vmstate_change(DeviceState *d, bool running)
>      VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
> 
>      if (running) {
> -        /* Try to find out if the guest has bus master disabled, but is
> -           in ready state. Then we have a buggy guest OS. */
> -        if ((vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
> +        /* Old QEMU versions did not set bus master enable on status write.
> +         * Detect DRIVER set and enable it.
> +         */
> +        if ((proxy->flags & VIRTIO_PCI_FLAG_BUS_MASTER_BUG_MIGRATION) &&
> +            (vdev->status & VIRTIO_CONFIG_S_DRIVER) &&
>              !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
> -            proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG;
> +            pci_default_write_config(&proxy->pci_dev, PCI_COMMAND,
> +                                     proxy->pci_dev.config[PCI_COMMAND] |
> +                                     PCI_COMMAND_MASTER, 1);
>          }
>          virtio_pci_start_ioeventfd(proxy);
>      } else {
> @@ -1040,10 +1032,11 @@ static void virtio_pci_reset(DeviceState *qdev)
>      virtio_pci_stop_ioeventfd(proxy);
>      virtio_bus_reset(bus);
>      msix_unuse_all_vectors(&proxy->pci_dev);
> -    proxy->flags &= ~VIRTIO_PCI_FLAG_BUS_MASTER_BUG;
>  }
> 
>  static Property virtio_pci_properties[] = {
> +    DEFINE_PROP_BIT("virtio-pci-bus-master-bug-migration", VirtIOPCIProxy, flags,
> +                    VIRTIO_PCI_FLAG_BUS_MASTER_BUG_MIGRATION_BIT, false),
>      DEFINE_VIRTIO_COMMON_FEATURES(VirtIOPCIProxy, host_features),
>      DEFINE_PROP_END_OF_LIST(),
>  };