Enabling a ACPI eMMC device is causing kernel reboots with FreeBSD 11.2

[Konstantin Belousov]

On Fri, Nov 16, 2018 at 10:45:39AM +0530, Rajesh Kumar wrote:
> Hi,
> 
> I did some study on this. During acpi_attach, if MCFG table is present,
> FreeBSD tries to use it (That is to map the PCI Base address to virtual
> address space).  Setting hw.pci.mcfg=0, disables that mapping and lets the
> system use the type 1 config access (which is IO port based access).  So,
> this is what hw.pci.mcfg does.
> 
> In our case, we are enabling a device on the ACPI bus and made sure no
> other ACPI device collides with the address range for PCI (which mcfg
> says). So, why enabling a device on ACPI, is causing the memory mapped PCI
> access go bad to panic/reboot the kernel?  I tried to collect more info
> enabling INVARIANTS, but in that case kernel panics much before in the boot
> process. So, how could I proceed in debugging this issue? Any suggestions?
There is no ACPI bus, at best the device is enumerated using ACPI.

> 
> 
> On Thu, Nov 8, 2018 at 4:14 PM Rajesh Kumar <rajfbsd at gmail.com> wrote:
> 
> > Hi,
> >
> > I have amd64 board, which has a eMMC device on the ACPI bus. When I try
> > booting FreeBSD 11.2 on this board, with eMMC device disabled in BIOS, it
> > boots without any issues.  But, when eMMC device is enabled in BIOS,
> > FreeBSD 11.2 continuously reboots.
What is the CPU in your motherboard ?
If it is AMD, try HEAD or latest 12.0 BETA.

> >
> > When I have the following tunable set, FreeBSD 11.2 boots without any
> > issues with eMMC enabled.
> > hw.pci.mcfg=0
> >
> > Observations :
> > a) We have verified the ACPI device addresses (from DSDT table) doesn't
> > conflict with the PCI address base (configured in MCFG table).
> > b) The PCI address base from MCFG table is read correctly by kernel
> > (Verbose boot prints that address). So, I don't think MCFG table pointer is
> > corrupted and getting read properly.
> >
> > Questions :
> > a) What does hw.pci.mcfg=0 actually do to get the reboot issue resolved?
> > b) Why enabling a device on ACPI bus needs hw.pci.mcfg (PCI specific) to
> > boot?
> >
> > Looks like the system reboots when the ACPI and PCI devices enumeration
> > starts during the boot. So, seems ACPI (or) PCI devices aren't getting
> > enough resources and so reboots.
> >
> > Thanks,
> > Rajesh.
> >
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