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

[Ani Sinha]

On Wed, 8 Sep 2021, 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?
>

Michael, we would need your inputs on this one.