Re: [PATCH] hw/i386/acpi-build: adjust q35 IO addr range for acpi pci hotplug

[Michael S. Tsirkin]

On Wed, Sep 08, 2021 at 10:43:51AM +0200, Igor Mammedov wrote:
> On Wed, 8 Sep 2021 12:51:04 +0530 (IST)
> Ani Sinha <ani@anisinha.ca> wrote:
> 
> > On Wed, 8 Sep 2021, Igor Mammedov wrote:
> > 
> > > On Wed,  8 Sep 2021 09:41:39 +0530
> > > Ani Sinha <ani@anisinha.ca> wrote:
> > >  
> > > > Change caf108bc58790 ("hw/i386/acpi-build: Add ACPI PCI hot-plug 
> > > > methods to Q35")
> > > > selects an IO address range for acpi based PCI hotplug for q35 
> > > > arbitrarily. It
> > > > starts at address 0x0cc4 and ends at 0x0cdb. It was assumed that this 
> > > > address
> > > > range was free and available. However, upon more testing, it seems this 
> > > > address
> > > > range to be not available for some latest versions of windows.  
> > >
> > > The range is something assigned by QEMU, and guest has no say where it 
> > > should be.
> > > but perhaps we failed to describe it properly or something similar, so 
> > > one gets
> > > 'no resource' error.  
> > 
> > OK dug deeper. The existing range of IO address conflicts with the CPU
> > hotplug range.
> > 
> > CPU hotplug range (ICH9_CPU_HOTPLUG_IO_BASE) is 0x0cd8 to 0x0ce3
> > 
> > This intersects with range 0x0cc4 to 0x0cdb for ACPI_PCIHP_ADDR_ICH9 .
> 
> Looking at 'info mtree' it's indeed wrong:
> 
>     0000000000000cc4-0000000000000cdb (prio 0, i/o): acpi-pci-hotplug
>     0000000000000cd8-0000000000000cf7 (prio 0, i/o): acpi-cpu-hotplug
> 
> which of them eventually handles IO request in intersection range?
> 
> Please, add to commit message your findings, so it would point out
> where problem comes from and what it breaks(doesn't work as expect).
> 
> Given it's broken to begin with (and possibly regression if it broke cpu 
> hotplug),
> I'm inclined to fix it without adding compat stuff.
> Michael, what do you think?

Agreed.

> > We need to change one or the other.
> > 
> > From the windows device manager, I see that the other IO address range is
> > 0x0620 to 0x062F which is reserved for GPE0.
> > 
> > .
> > > We need a find out a reason why Windows doesn't like it. You might get 
> > > more
> > > detailed error running Windows debug build with ACPI debugger attached.  
> > 
> > bummer. This is beyond my expertize and I do not have a windows debug
> > build.
> never mind, you already found the issue.
>   
> > > > Hence, this
> > > > change modifies the IO address range so that windows can allocate the 
> > > > address
> > > > range without any conflict. The new address range would start at 0x0dd4 
> > > > and end
> > > > at address 0x0deb.
> > > >
> > > > This change has been tested using a Windows Server 2019 guest VM.
> > > >
> > > > Fixes: caf108bc58790 ("hw/i386/acpi-build: Add ACPI PCI hot-plug 
> > > > methods to Q35")
> > > > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/561
> > > >
> > > > Signed-off-by: Ani Sinha <ani@anisinha.ca>
> > > > ---
> > > >  include/hw/acpi/ich9.h | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/include/hw/acpi/ich9.h b/include/hw/acpi/ich9.h
> > > > index a329ce43ab..b68c5a2174 100644
> > > > --- a/include/hw/acpi/ich9.h
> > > > +++ b/include/hw/acpi/ich9.h
> > > > @@ -29,7 +29,7 @@
> > > >  #include "hw/acpi/acpi_dev_interface.h"
> > > >  #include "hw/acpi/tco.h"
> > > >
> > > > -#define ACPI_PCIHP_ADDR_ICH9 0x0cc4
> > > > +#define ACPI_PCIHP_ADDR_ICH9 0x0dd4
> maybe 0xcc0 to fit right under acpi-cpu-hotplug as it was intended?
> 
> > >
> > > that's ABI change, it must be versioned
> > >  
> > > >
> > > >  typedef struct ICH9LPCPMRegs {
> > > >      /*  
> > >
> > >  
> >