Re: [Qemu-devel] [PATCH v4 3/5] acpi: pc: add fw_cfg device node to ssdt

[Gabriel L. Somlo]

On Thu, Oct 01, 2015 at 01:52:59PM +0200, Laszlo Ersek wrote:
> On 10/01/15 13:33, Igor Mammedov wrote:
> > On Thu, 1 Oct 2015 10:27:15 +0200
> > Laszlo Ersek <address@hidden> wrote:
> > 
> >> On 10/01/15 09:02, Igor Mammedov wrote:
> >>> On Sun, 27 Sep 2015 17:29:00 -0400
> >>> "Gabriel L. Somlo" <address@hidden> wrote:
> >>>
> >>>> Add a fw_cfg device node to the ACPI SSDT, on machine types
> >>>> pc-*-2.5 and up. While the guest-side BIOS can't utilize
> >>>> this information (since it has to access the hard-coded
> >>>> fw_cfg device to extract ACPI tables to begin with), having
> >>>> fw_cfg listed in ACPI will help the guest kernel keep a more
> >>>> accurate inventory of in-use IO port regions.
> >>>>
> >>>> Signed-off-by: Gabriel Somlo <address@hidden>
> >>>> ---
> >>>>  hw/i386/acpi-build.c | 23 +++++++++++++++++++++++
> >>>>  hw/i386/pc_piix.c    |  1 +
> >>>>  hw/i386/pc_q35.c     |  1 +
> >>>>  include/hw/i386/pc.h |  1 +
> >>>>  4 files changed, 26 insertions(+)
> >>>>
> >>>> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> >>>> index 95e0c65..ece2710 100644
> >>>> --- a/hw/i386/acpi-build.c
> >>>> +++ b/hw/i386/acpi-build.c
> >>>> @@ -906,6 +906,7 @@ build_ssdt(GArray *table_data, GArray *linker,
> >>>>             PcPciInfo *pci, PcGuestInfo *guest_info)
> >>>>  {
> >>>>      MachineState *machine = MACHINE(qdev_get_machine());
> >>>> +    PCMachineClass *pcmc = PC_MACHINE_GET_CLASS(machine);
> >>>>      uint32_t nr_mem = machine->ram_slots;
> >>>>      unsigned acpi_cpus = guest_info->apic_id_limit;
> >>>>      Aml *ssdt, *sb_scope, *scope, *pkg, *dev, *method, *crs, *field, 
> >>>> *ifctx;
> >>>> @@ -1071,6 +1072,28 @@ build_ssdt(GArray *table_data, GArray *linker,
> >>>>      aml_append(scope, aml_name_decl("_S5", pkg));
> >>>>      aml_append(ssdt, scope);
> >>>>  
> >>>> +    if (!pcmc->acpi_no_fw_cfg_node) {
> >>> we don't really care about SSDT size changes since during
> >>> migration ACPI blobs will be migrated from source, so
> >>> machine compat bloat is excessive here. It would be better
> >>> to just remove it.
> >>
> >> This was Eduardo's suggestion, if I recall correctly:
> >>
> >> http://thread.gmane.org/gmane.comp.emulators.qemu/361930/focus=361983
> >>
> >> The idea being, if you move a guest from older QEMU to newer QEMU, but
> >> keep the machine type (or more precisely, the full machine config, like
> >> the domain XML) intact, the ACPI device node should not appear out of
> >> the blue.
> > This ACPI device is an always used resource declaration regardless
> > of machine type so it makes sense to tell guest about used resource.
> > 
> > The only reason for machine compat code would be if guest suddenly
> > started to ask for a driver but as Gabriel showed with _STA(0xB)
> > it doesn't, so I'm trying to keep ACPI code machine compat agnostic
> > as much as possible.
> 
> Fine by me, but I think Eduardo should agree (or disagree) as well,
> because it was his point originally.

I have no problem taking the compat logic back out, if Eduardo agrees
that's an OK thing to do.

> >>>> +        scope = aml_scope("\\_SB");
> >>>> +        dev = aml_device("FWCF");
> >>>> +
> >>>> +        aml_append(dev, aml_name_decl("_HID", aml_string("QEMU0002")));
> >>>> +        /* device present, functioning, decoding, not shown in UI */
> >>>> +        aml_append(dev, aml_name_decl("_STA", aml_int(0xB)));
> >>>> +
> >>>> +        crs = aml_resource_template();
> >>>> +        /* when using port i/o, the 8-bit data register *always* 
> >>>> overlaps
> >>>> +         * with half of the 16-bit control register. Hence, the total 
> >>>> size
> >>>> +         * of the i/o region used is FW_CFG_CTL_SIZE */
> >>>> +        aml_append(crs,
> >>>> +            aml_io(AML_DECODE16, FW_CFG_IO_BASE, FW_CFG_IO_BASE,
> >>>> +                   0x01, FW_CFG_CTL_SIZE)
> >>>> +        );
> >>> could you check/dump this _CRS and PCI0._CRS to see if they are 
> >>> intersecting
> >>> in any way?

On bot PIIX and Q35, there's no _CRS under PCI0 in the dsdt.
All I could find was

Scope (\_SB.PCI0)
{
    Name (_CRS, ...)
        IO (Decode16,
            0x0CF8,             // Range Minimum
            0x0CF8,             // Range Maximum
            0x01,               // Alignment
            0x08,               // Length
            )
    ...

So that does not overlap with fw_cfg.

In fact, I searched for all "IO (Decode..." occurrences, and nothing
in either DSDT or SSDT has any overlap with [ 0x510 .. 0x512 ].

Thanks,
 -- Gabriel


> >>>
> >>>
> >>>> +        aml_append(dev, aml_name_decl("_CRS", crs));
> >>>> +
> >>>> +        aml_append(scope, dev);
> >>>> +        aml_append(ssdt, scope);
> >>>> +    }
> >>>> +
> >>>>      if (misc->applesmc_io_base) {
> >>>>          scope = aml_scope("\\_SB.PCI0.ISA");
> >>>>          dev = aml_device("SMC");
> >>>> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> >>>> index 3ffb05f..7f5e5d9 100644
> >>>> --- a/hw/i386/pc_piix.c
> >>>> +++ b/hw/i386/pc_piix.c
> >>>> @@ -482,6 +482,7 @@ static void 
> >>>> pc_i440fx_2_4_machine_options(MachineClass *m)
> >>>>      m->alias = NULL;
> >>>>      m->is_default = 0;
> >>>>      pcmc->broken_reserved_end = true;
> >>>> +    pcmc->acpi_no_fw_cfg_node = true;
> >>>>      SET_MACHINE_COMPAT(m, PC_COMPAT_2_4);
> >>>>  }
> >>>>  
> >>>> diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
> >>>> index 1b7d3b6..7180ca3 100644
> >>>> --- a/hw/i386/pc_q35.c
> >>>> +++ b/hw/i386/pc_q35.c
> >>>> @@ -385,6 +385,7 @@ static void pc_q35_2_4_machine_options(MachineClass 
> >>>> *m)
> >>>>      pc_q35_2_5_machine_options(m);
> >>>>      m->alias = NULL;
> >>>>      pcmc->broken_reserved_end = true;
> >>>> +    pcmc->acpi_no_fw_cfg_node = true;
> >>>>      SET_MACHINE_COMPAT(m, PC_COMPAT_2_4);
> >>>>  }
> >>>>  
> >>>> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> >>>> index 86007e3..6d0f1bd 100644
> >>>> --- a/include/hw/i386/pc.h
> >>>> +++ b/include/hw/i386/pc.h
> >>>> @@ -62,6 +62,7 @@ struct PCMachineClass {
> >>>>      bool broken_reserved_end;
> >>>>      HotplugHandler *(*get_hotplug_handler)(MachineState *machine,
> >>>>                                             DeviceState *dev);
> >>>> +    bool acpi_no_fw_cfg_node;
> >>>>  };
> >>>>  
> >>>>  #define TYPE_PC_MACHINE "generic-pc-machine"
> >>>
> >>
> > 
>