Re: [Qemu-devel] [PATCH v4 3/7] fw-cfg: expose "file_slots" parameter in fw_cfg_init_io_dma()

[Laszlo Ersek]

Mark, Artyom, do the sun4u machines support any kind of migration, given
that they are not versioned?

Alex, David, do the mac_newworld / mac_oldworld machines support
migration, given that they are not versioned?

Thanks
Laszlo

On 12/06/16 17:46, Laszlo Ersek wrote:
> On 12/06/16 12:49, Igor Mammedov wrote:
>> On Thu,  1 Dec 2016 18:06:20 +0100
>> Laszlo Ersek <address@hidden> wrote:
>>
>>> Accordingly, generalize the "file_slots" minimum calculation in
>>> fw_cfg_init_io_dma(), and move the constant FW_CFG_FILE_SLOTS_TRAD
>>> argument to the callers of fw_cfg_init_io_dma().
>> If I get idea correctly you're extending fw_cfg_init_io_dma() and
>> setting
>>  qdev_prop_set_uint32(dev, "file_slots", file_slots);
>> manually to keep old fw_cfg_init_io() the same without touching
>> xen/sun4u machines.
> 
> First, to my knowledge, Xen does not use fw_cfg. The following call
> chains depend on (!xen_enabled()):
> 
> pc_init1() | pc_q35_init()
>   if (!xen_enabled()):
>     pc_memory_init()
>       bochs_bios_init()
>         fw_cfg_init_io_dma()
> 
> Second, I wanted to keep the fw_cfg_init_io() call sites un-touched. In
> this patch, the fw_cfg_init_io() function passes an additional /
> internal-only parameter to fw_cfg_init_io_dma(), and the unconditional
> qdev_prop_set_uint32() call in fw_cfg_init_io_dma() is replaced with a
> conditional one (so that the property can only be lowered, not raised,
> by board code).
> 
>> That way we would have 2 different ways to set defaults
>> per machine type/version rather then the single COMPAT property way.
>>
>> How about dropping this patch and adding
>>  SET_MACHINE_COMPAT
>> to xen/sun4u machines instead and dropping fw_cfg_init_io() in
>> favor of fw_cfg_init_io_dma() along the way.
> 
> For the conditional qdev_prop_set_uint32() call, added in this patch, I
> used commit e6915b5f3a87 ("fw_cfg: unbreak migration compatibility for
> 2.4 and earlier machines") as model. According to that model, I couldn't
> drop this patch completely, because the new feature -- i.e., DMA in that
> patch, and higher fw_cfg file slots in this patch -- depends on both
> machine versions and board opt-in.
> 
> However, if we agree (according to your feedback on patch v4 2/7) that
> we will silently bump the fw_cfg file count for all new machine
> versions, without requiring (or permitting) board opt-in / opt-out, then
> I agree your above suggestion is consistent with that.
> 
> I think I don't have to drop fw_cfg_init_io() actually. But, with the
> board opt-in going away, I can drop both the additional "file_slots"
> parameter in fw_cfg_init_io_dma(), and the qdev_prop_set_uint32() call
> in it (even the unconditional one).
> 
> In fact I like this simplicity more, I just wanted to be extra cautious
> in the first version of the series that turned file_slots into a property.
> 
> ... Actually, are sun4u machines versioned? Hm... "hw/sparc64/sun4u.c"
> doesn't seem to define versioned machine types. Doesn't that imply that
> migration is *completely* unsupported for sun4u? Because, if that's the
> case, then I wouldn't even have to add SET_MACHINE_COMPAT().
> 
> Thanks!
> Laszlo
> 
>>
>>>
>>> Cc: "Gabriel L. Somlo" <address@hidden>
>>> Cc: "Michael S. Tsirkin" <address@hidden>
>>> Cc: Gerd Hoffmann <address@hidden>
>>> Cc: Igor Mammedov <address@hidden>
>>> Cc: Paolo Bonzini <address@hidden>
>>> Signed-off-by: Laszlo Ersek <address@hidden>
>>> ---
>>>  docs/specs/fw_cfg.txt     |  4 ++--
>>>  include/hw/nvram/fw_cfg.h |  2 +-
>>>  hw/i386/pc.c              |  3 ++-
>>>  hw/nvram/fw_cfg.c         | 13 ++++++-------
>>>  4 files changed, 11 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/docs/specs/fw_cfg.txt b/docs/specs/fw_cfg.txt
>>> index 84e2978706f5..4a6888b511f4 100644
>>> --- a/docs/specs/fw_cfg.txt
>>> +++ b/docs/specs/fw_cfg.txt
>>> @@ -153,12 +153,12 @@ Selector Reg.    Range Usage
>>>  0x4000 - 0x7fff  Generic (0x0000 - 0x3fff, RW, ignored in QEMU v2.4+)
>>>  0x8000 - 0xbfff  Arch. Specific (0x0000 - 0x3fff, generally RO, possibly RW
>>>                                   through the DMA interface in QEMU v2.9+)
>>>  0xc000 - 0xffff  Arch. Specific (0x0000 - 0x3fff, RW, ignored in v2.4+)
>>>  
>>> -In practice, the number of allowed firmware configuration items is given
>>> -by the value (FW_CFG_FILE_FIRST + FW_CFG_FILE_SLOTS_TRAD) (see fw_cfg.h).
>>> +In practice, the number of allowed firmware configuration items depends on 
>>> the
>>> +machine type.
>> machine type/version
>>
>>>  
>>>  = Guest-side DMA Interface =
>>>  
>>>  If bit 1 of the feature bitmap is set, the DMA interface is present. This 
>>> does
>>>  not replace the existing fw_cfg interface, it is an add-on. This interface
>>> diff --git a/include/hw/nvram/fw_cfg.h b/include/hw/nvram/fw_cfg.h
>>> index b980cbaebf43..e9a6b6aa968c 100644
>>> --- a/include/hw/nvram/fw_cfg.h
>>> +++ b/include/hw/nvram/fw_cfg.h
>>> @@ -173,11 +173,11 @@ void fw_cfg_add_file_callback(FWCfgState *s, const 
>>> char *filename,
>>>   */
>>>  void *fw_cfg_modify_file(FWCfgState *s, const char *filename, void *data,
>>>                           size_t len);
>>>  
>>>  FWCfgState *fw_cfg_init_io_dma(uint32_t iobase, uint32_t dma_iobase,
>>> -                                AddressSpace *dma_as);
>>> +                                AddressSpace *dma_as, uint32_t file_slots);
>>>  FWCfgState *fw_cfg_init_io(uint32_t iobase);
>>>  FWCfgState *fw_cfg_init_mem(hwaddr ctl_addr, hwaddr data_addr);
>>>  FWCfgState *fw_cfg_init_mem_wide(hwaddr ctl_addr,
>>>                                   hwaddr data_addr, uint32_t data_width,
>>>                                   hwaddr dma_addr, AddressSpace *dma_as);
>>> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
>>> index a9e64a88e5e7..5d929d8fc887 100644
>>> --- a/hw/i386/pc.c
>>> +++ b/hw/i386/pc.c
>>> @@ -741,11 +741,12 @@ static FWCfgState *bochs_bios_init(AddressSpace *as, 
>>> PCMachineState *pcms)
>>>  {
>>>      FWCfgState *fw_cfg;
>>>      uint64_t *numa_fw_cfg;
>>>      int i, j;
>>>  
>>> -    fw_cfg = fw_cfg_init_io_dma(FW_CFG_IO_BASE, FW_CFG_IO_BASE + 4, as);
>>> +    fw_cfg = fw_cfg_init_io_dma(FW_CFG_IO_BASE, FW_CFG_IO_BASE + 4, as,
>>> +                                FW_CFG_FILE_SLOTS_TRAD);
>>>      fw_cfg_add_i16(fw_cfg, FW_CFG_NB_CPUS, pcms->boot_cpus);
>>>  
>>>      /* FW_CFG_MAX_CPUS is a bit confusing/problematic on x86:
>>>       *
>>>       * For machine types prior to 1.8, SeaBIOS needs FW_CFG_MAX_CPUS for
>>> diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
>>> index 2e1441c09750..c33c76ab93b1 100644
>>> --- a/hw/nvram/fw_cfg.c
>>> +++ b/hw/nvram/fw_cfg.c
>>> @@ -926,11 +926,11 @@ static void fw_cfg_init1(DeviceState *dev)
>>>      s->machine_ready.notify = fw_cfg_machine_ready;
>>>      qemu_add_machine_init_done_notifier(&s->machine_ready);
>>>  }
>>>  
>>>  FWCfgState *fw_cfg_init_io_dma(uint32_t iobase, uint32_t dma_iobase,
>>> -                                AddressSpace *dma_as)
>>> +                                AddressSpace *dma_as, uint32_t file_slots)
>>>  {
>>>      DeviceState *dev;
>>>      FWCfgState *s;
>>>      uint32_t version = FW_CFG_VERSION;
>>>      bool dma_requested = dma_iobase && dma_as;
>>> @@ -940,15 +940,14 @@ FWCfgState *fw_cfg_init_io_dma(uint32_t iobase, 
>>> uint32_t dma_iobase,
>>>      qdev_prop_set_uint32(dev, "dma_iobase", dma_iobase);
>>>      if (!dma_requested) {
>>>          qdev_prop_set_bit(dev, "dma_enabled", false);
>>>      }
>>>  
>>> -    /* Once we expose the "file_slots" property to callers of
>>> -     * fw_cfg_init_io_dma(), the following setting should become 
>>> conditional on
>>> -     * the input parameter being lower than the current value of the 
>>> property.
>>> -     */
>>> -    qdev_prop_set_uint32(dev, "file_slots", FW_CFG_FILE_SLOTS_TRAD);
>>> +    if (file_slots < object_property_get_int(OBJECT(dev), "file_slots",
>>> +                                             &error_abort)) {
>>> +        qdev_prop_set_uint32(dev, "file_slots", file_slots);
>>> +    }
>>>  
>>>      fw_cfg_init1(dev);
>>>      s = FW_CFG(dev);
>>>  
>>>      if (s->dma_enabled) {
>>> @@ -964,11 +963,11 @@ FWCfgState *fw_cfg_init_io_dma(uint32_t iobase, 
>>> uint32_t dma_iobase,
>>>      return s;
>>>  }
>>>  
>>>  FWCfgState *fw_cfg_init_io(uint32_t iobase)
>>>  {
>>> -    return fw_cfg_init_io_dma(iobase, 0, NULL);
>>> +    return fw_cfg_init_io_dma(iobase, 0, NULL, FW_CFG_FILE_SLOTS_TRAD);
>>>  }
>>>  
>>>  FWCfgState *fw_cfg_init_mem_wide(hwaddr ctl_addr,
>>>                                   hwaddr data_addr, uint32_t data_width,
>>>                                   hwaddr dma_addr, AddressSpace *dma_as)
>>
>