Re: [Qemu-arm] [Qemu-devel] [PATCH v8 3/5] acpi: pc: add fw_cfg device node to dsdt

[Gabriel L. Somlo]

On Fri, Feb 19, 2016 at 02:49:53PM +0100, Igor Mammedov wrote:
> On Thu, 11 Feb 2016 17:06:03 -0500
> "Gabriel L. Somlo" <address@hidden> wrote:
> 
> > Add a fw_cfg device node to the ACPI DSDT. While the guest-side
> > firmware 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>
> > Reviewed-by: Laszlo Ersek <address@hidden>
> > Reviewed-by: Marc Marí <address@hidden>
> > ---
> >  hw/i386/acpi-build.c | 29 +++++++++++++++++++++++++++++
> >  1 file changed, 29 insertions(+)
> > 
> > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> > index 4554eb8..4762fd2 100644
> > --- a/hw/i386/acpi-build.c
> > +++ b/hw/i386/acpi-build.c
> > @@ -2190,6 +2190,35 @@ build_dsdt(GArray *table_data, GArray *linker,
> >      aml_append(scope, aml_name_decl("_S5", pkg));
> >      aml_append(dsdt, scope);
> >  
> > +    /* create fw_cfg node, unconditionally */
> > +    {
> > +        /* 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; when using DMA, the
> > +         * DMA control register is located at FW_CFG_DMA_IO_BASE + 4 */
> > +        uint8_t io_size = object_property_get_bool(OBJECT(pcms->fw_cfg),
> > +                                                   "dma_enabled", NULL) ?
> > +                          ROUND_UP(FW_CFG_CTL_SIZE, 4) + 
> > sizeof(dma_addr_t) :
> > +                          FW_CFG_CTL_SIZE;
> > +
> > +        scope = aml_scope("\\_SB");
> > +        dev = aml_device("FWCF");
> > +
> > +        aml_append(dev, aml_name_decl("_HID", aml_string("QEMU0002")));
> From my tests with different Windows versions, it doesn't prevent
> WS2003 and WS2008 from showing a prompt for unknown device that asks for a 
> driver.

I installed windows 2008 server r2 64bit, on both pc and q35 machines,
and still only saw the "unknown device" in the Device Manager after
forcing _STA to 0xF (instead of 0xB).

> One however could shut it up by allowing OS look for a driver
> which is not found and then tell  not to ask for it anymore.

It's entirely possible that "after a while" something would pop up and
ask for a driver anyway. I did try to "humor it" by allowing it to
search for a driver, and it failed, and the device was still showing
up as unknown (remember, this is with _STA set to 0xF, which I did
only to force it to show up :)

I never waited around long enough for it to prompt me, so that may be
the difference between our tests...

> 
> So existing users will have to perform this action once
> they have migrated to newer QEMU regardless of machine version.
> 
> > +
> > +        /* device present, functioning, decoding, not shown in UI */
> > +        aml_append(dev, aml_name_decl("_STA", aml_int(0xB)));
> > +
> > +        crs = aml_resource_template();
> > +        aml_append(crs,
> > +            aml_io(AML_DECODE16, FW_CFG_IO_BASE, FW_CFG_IO_BASE, 0x01, 
> > io_size)
> > +        );
> that creates \_SB.FWCF._CRS 
> +            Name (_CRS, ResourceTemplate ()  // _CRS: Current Resource 
> Settings
> +            {
> +                IO (Decode16,
> +                    0x0510,             // Range Minimum
> +                    0x0510,             // Range Maximum
> +                    0x01,               // Alignment
> +                    0x0C,               // Length
> +                    )
> +            })
> 
> which collides with \_SB.PCI0._CRS
>             WordIO (ResourceProducer, MinFixed, MaxFixed, PosDecode, 
> EntireRange,
>                 0x0000,             // Granularity
>                 0x0000,             // Range Minimum
>                 0x0CF7,             // Range Maximum
>                 0x0000,             // Translation Offset
>                 0x0CF8,
> 
> that shouldn't happen, and solution for this is to put
> FWCF device descriptor in \_SB.PCI0 scope so FWCF would consume
> from PCI0 IO range.
> 
> That won't help Windows to notice a conflict, if there is any,
> as there aren't any drivers for QEMU0002 device but at least
> when Windows gets a driver it won't crash due above conflict.

OK, so the difference between "\_SB" and "\_SB.PCI0" is that, with
_STA forced to 0xF, the "resources" tab of the "unknown device" no
longer shows conflicts on the IO range of 510-518.

With that being said, I still hope most people won't ever make it this
far (with _STA set to 0xB). But in case they ever do, yes, placing
FWCF in \_SB.PCI0 should take care of it -- thanks for showing me that!

V9 (coming up soon) should reflect that change.

Thanks much,
--Gabriel

> 
> > +        aml_append(dev, aml_name_decl("_CRS", crs));
> > +
> > +        aml_append(scope, dev);
> > +        aml_append(dsdt, scope);
> > +    }
> > +
> >      if (misc->applesmc_io_base) {
> >          scope = aml_scope("\\_SB.PCI0.ISA");
> >          dev = aml_device("SMC");
>