debian/patches/extra/fw_cfg-unbreak-migration-compatibility-for-2.4.patch

   1 From patchwork Thu Feb 18 19:31:00 2016
   2 Content-Type: text/plain; charset="utf-8"
   3 MIME-Version: 1.0
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   5 Subject: fw_cfg: unbreak migration compatibility for 2.4 and earlier machines
   6 From: Laszlo Ersek <lersek@redhat.com>
   7 X-Patchwork-Id: 584876
   8 Message-Id: <1455823860-22268-1-git-send-email-lersek@redhat.com>
   9 To: qemu-devel@nongnu.org
  10 Cc: =?UTF-8?q?Marc=20Mar=ED?= <markmb@redhat.com>,
  11  Gerd Hoffmann <kraxel@redhat.com>,
  12  Alexandre DERUMIER <aderumier@odiso.com>, qemu-stable@nongnu.org
  13 Date: Thu, 18 Feb 2016 20:31:00 +0100
  14
  15 When I reviewed Marc's fw_cfg DMA patches, I completely missed that the
  16 way we set dma_enabled would break migration.
  17
  18 Gerd explained the right way (see reference below): dma_enabled should be
  19 set to true by default, and only true->false transitions should be
  20 possible:
  21
  22 - when the user requests that with
  23
  24     -global fw_cfg_mem.dma_enabled=off
  25
  26   or
  27
  28    -global fw_cfg_io.dma_enabled=off
  29
  30   as appropriate for the platform,
  31
  32 - when HW_COMPAT_2_4 dictates it,
  33
  34 - when board code initializes fw_cfg without requesting DMA support.
  35
  36 Cc: Marc Marí <markmb@redhat.com>
  37 Cc: Gerd Hoffmann <kraxel@redhat.com>
  38 Cc: Alexandre DERUMIER <aderumier@odiso.com>
  39 Cc: qemu-stable@nongnu.org
  40 Ref: http://thread.gmane.org/gmane.comp.emulators.qemu/390272/focus=391042
  41 Ref: https://bugs.launchpad.net/qemu/+bug/1536487
  42 Suggested-by: Gerd Hoffmann <kraxel@redhat.com>
  43 Signed-off-by: Laszlo Ersek <lersek@redhat.com>
  44 ---
  45
  46 Notes:
  47     Tested the following cases with gdb, using qemu-system-x86_64, setting a
  48     breakpoint on (s->dma_enabled) in fw_cfg_init_io_dma():
  49
  50     * no special params (DMA enabled)
  51     * -global fw_cfg_io.dma_enabled=off (DMA disabled)
  52     * -M pc-i440fx-2.4 (DMA disabled), similarly with 2.3 and Q35 too
  53
  54     Also tested the memory mapped case in practice, using
  55     qemu-system-aarch64 -M virt, -kernel / -initrd / -append, with guest
  56     UEFI:
  57     * no special params (DMA enabled)
  58     * -global fw_cfg_mem.dma_enabled=off (DMA disabled)
  59
  60     Not tested:
  61     * actual migration
  62     * when board code doesn't request DMA support
  63
  64     Testing feedback from people who use migration would be nice.
  65
  66  include/hw/compat.h |  8 ++++++++
  67  hw/nvram/fw_cfg.c   | 20 ++++++++++++--------
  68  2 files changed, 20 insertions(+), 8 deletions(-)
  69
  70 diff --git a/include/hw/compat.h b/include/hw/compat.h
  71 index 2ebe739fcb5c..a5dbbf8984b1 100644
  72 index d0b1c4f..b7973db 100644
  73 --- a/include/hw/compat.h
  74 +++ b/include/hw/compat.h
  75 @@ -18,6 +18,14 @@
  76              .driver   = "virtio-pci",\
  77              .property = "migrate-extra",\
  78              .value    = "off",\
  79 +        },{\
  80 +            .driver   = "fw_cfg_mem",\
  81 +            .property = "dma_enabled",\
  82 +            .value    = "off",\
  83 +        },{\
  84 +            .driver   = "fw_cfg_io",\
  85 +            .property = "dma_enabled",\
  86 +            .value    = "off",\
  87          },
  88
  89  #define HW_COMPAT_2_3 \
  90 diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
  91 index 79c5742b3362..f3acb47bd4dc 100644
  92 --- a/hw/nvram/fw_cfg.c
  93 +++ b/hw/nvram/fw_cfg.c
  94 @@ -778,17 +778,19 @@ FWCfgState *fw_cfg_init_io_dma(uint32_t iobase, uint32_t dma_iobase,
  95      DeviceState *dev;
  96      FWCfgState *s;
  97      uint32_t version = FW_CFG_VERSION;
  98 -    bool dma_enabled = dma_iobase && dma_as;
  99 +    bool dma_requested = dma_iobase && dma_as;
 100
 101      dev = qdev_create(NULL, TYPE_FW_CFG_IO);
 102      qdev_prop_set_uint32(dev, "iobase", iobase);
 103      qdev_prop_set_uint32(dev, "dma_iobase", dma_iobase);
 104 -    qdev_prop_set_bit(dev, "dma_enabled", dma_enabled);
 105 +    if (!dma_requested) {
 106 +        qdev_prop_set_bit(dev, "dma_enabled", false);
 107 +    }
 108
 109      fw_cfg_init1(dev);
 110      s = FW_CFG(dev);
 111
 112 -    if (dma_enabled) {
 113 +    if (s->dma_enabled) {
 114          /* 64 bits for the address field */
 115          s->dma_as = dma_as;
 116          s->dma_addr = 0;
 117 @@ -814,11 +816,13 @@ FWCfgState *fw_cfg_init_mem_wide(hwaddr ctl_addr,
 118      SysBusDevice *sbd;
 119      FWCfgState *s;
 120      uint32_t version = FW_CFG_VERSION;
 121 -    bool dma_enabled = dma_addr && dma_as;
 122 +    bool dma_requested = dma_addr && dma_as;
 123
 124      dev = qdev_create(NULL, TYPE_FW_CFG_MEM);
 125      qdev_prop_set_uint32(dev, "data_width", data_width);
 126 -    qdev_prop_set_bit(dev, "dma_enabled", dma_enabled);
 127 +    if (!dma_requested) {
 128 +        qdev_prop_set_bit(dev, "dma_enabled", false);
 129 +    }
 130
 131      fw_cfg_init1(dev);
 132
 133 @@ -828,7 +832,7 @@ FWCfgState *fw_cfg_init_mem_wide(hwaddr ctl_addr,
 134
 135      s = FW_CFG(dev);
 136
 137 -    if (dma_enabled) {
 138 +    if (s->dma_enabled) {
 139          s->dma_as = dma_as;
 140          s->dma_addr = 0;
 141          sysbus_mmio_map(sbd, 2, dma_addr);
 142 @@ -873,7 +877,7 @@ static Property fw_cfg_io_properties[] = {
 143      DEFINE_PROP_UINT32("iobase", FWCfgIoState, iobase, -1),
 144      DEFINE_PROP_UINT32("dma_iobase", FWCfgIoState, dma_iobase, -1),
 145      DEFINE_PROP_BOOL("dma_enabled", FWCfgIoState, parent_obj.dma_enabled,
 146 -                     false),
 147 +                     true),
 148      DEFINE_PROP_END_OF_LIST(),
 149  };
 150
 151 @@ -913,7 +917,7 @@ static const TypeInfo fw_cfg_io_info = {
 152  static Property fw_cfg_mem_properties[] = {
 153      DEFINE_PROP_UINT32("data_width", FWCfgMemState, data_width, -1),
 154      DEFINE_PROP_BOOL("dma_enabled", FWCfgMemState, parent_obj.dma_enabled,
 155 -                     false),
 156 +                     true),
 157      DEFINE_PROP_END_OF_LIST(),
 158  };
 159