Re: [Qemu-devel] [PATCH v2 3/5] acpi: pc: add fw_cfg device node to ssdt

[Gabriel L. Somlo]

On Mon, Sep 14, 2015 at 01:09:41PM -0300, Eduardo Habkost wrote:
> On Mon, Sep 14, 2015 at 10:57:31AM -0400, Gabriel L. Somlo wrote:
> > Add a fw_cfg device node to the ACPI SSDT. 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 | 20 ++++++++++++++++++++
> >  1 file changed, 20 insertions(+)
> > 
> > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> > index 95e0c65..ecdb3a5 100644
> > --- a/hw/i386/acpi-build.c
> > +++ b/hw/i386/acpi-build.c
> > @@ -1071,6 +1071,26 @@ build_ssdt(GArray *table_data, GArray *linker,
> >      aml_append(scope, aml_name_decl("_S5", pkg));
> >      aml_append(ssdt, scope);
> >  
> > +    if (guest_info->fw_cfg) {
> 
> I sent a reply to v1 a few minutes before seeing v2. Copying it here for
> reference:
> 
> Is this function ever going to be called without fw_cfg set?
> acpi_setup() returns immediately if fw_cfg isn't available.

You're right, build_ssdt() is called from acpi_build(), which is
called directly from acpi_setup(), and also indirectly via
acpi_build_update() via acpi_add_rom_blob(), but all that eventually
ties back to acpi_setup(), *after* it already established that
guest_info->fw_cfg is non-NULL.

> Also, this changes guest ABI, so you will need to add some compat flag
> to PCMachineClass indicating if the device node should be added.

So I'll replace the "if (guest_info->fw_cfg)" check with
"if machine-type >= (pc-q35-2.5 or pc-i440fx-2.5))", in v3,
as soon as the patches for the 2.5 machine type make it into
git master (I remember seeing a reviewed-by fly by for that
earlier today :)

Thanks much,
--Gabriel

> 
> 
> > +        scope = aml_scope("\\_SB");
> > +        dev = aml_device("FWCF");
> > +
> > +        aml_append(dev, aml_name_decl("_HID", aml_string("QEMU0002")));
> > +
> > +        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)
> > +        );
> > +        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");
> > -- 
> > 2.4.3
> > 
> 
> -- 
> Eduardo