Add support for ACPI Module Device ACPI0004?

[Dexuan Cui]

The ACPI firmware of Hyper-V UEFI VM has a Module Device whose Hardware
ID is "ACPI0004". The module device has a _CRS object defining some MMIO
ranges, which are needed when physical PCIe devices are passed through
to the VM.

Currently it looks FreeBSD doesn't make use of the ACPI module device and
hence the _CRS object can't be easily retrieved by Hyper-V VMBus driver.

Can we add the support of "ACPI0004" with the below one-line change?

Looking forward to your suggestion!

--- a/sys/dev/acpica/acpi_resource.c
+++ b/sys/dev/acpica/acpi_resource.c
@@ -653,7 +653,7 @@ MODULE_DEPEND(acpi_sysresource, acpi, 1, 1, 1);
static int
acpi_sysres_probe(device_t dev)
{
- static char *sysres_ids[] = { "PNP0C01", "PNP0C02", NULL };
+ static char *sysres_ids[] = { "PNP0C01", "PNP0C02", "ACPI0004", NULL };

if (acpi_disabled("sysresource") ||
ACPI_ID_PROBE(device_get_parent(dev), dev, sysres_ids) == NULL)

Thanks,
-- Dexuan

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[John Baldwin]

On Wednesday, April 19, 2017 12:26:51 PM Dexuan Cui wrote:
> The ACPI firmware of Hyper-V UEFI VM has a Module Device whose Hardware
> ID is "ACPI0004". The module device has a _CRS object defining some MMIO
> ranges, which are needed when physical PCIe devices are passed through
> to the VM.
>
> Currently it looks FreeBSD doesn't make use of the ACPI module device and
> hence the _CRS object can't be easily retrieved by Hyper-V VMBus driver.
>
> Can we add the support of "ACPI0004" with the below one-line change?
>
> Looking forward to your suggestion!
>
> --- a/sys/dev/acpica/acpi_resource.c
> +++ b/sys/dev/acpica/acpi_resource.c
> @@ -653,7 +653,7 @@ MODULE_DEPEND(acpi_sysresource, acpi, 1, 1, 1);
> static int
> acpi_sysres_probe(device_t dev)
> {
> - static char *sysres_ids[] = { "PNP0C01", "PNP0C02", NULL };
> + static char *sysres_ids[] = { "PNP0C01", "PNP0C02", "ACPI0004", NULL };
>
> if (acpi_disabled("sysresource") ||
> ACPI_ID_PROBE(device_get_parent(dev), dev, sysres_ids) == NULL)

Hmm, so the role of C01 and C02 is to reserve system resources, though we
in turn allow any child of acpi0 to suballocate those ranges (since historically
c01 and c02 tend to allocate I/O ranges that are then used by things like the
EC, PS/2 keyboard controller, etc.). From my reading of ACPI0004 in the ACPI
6.1 spec it's not quite clear that ACPI0004 is like that? In particular, it
seems that 004 should only allow direct children to suballocate? This change
might work, but it will allow more devices to allocate the ranges in _CRS
than otherwise.

Do you have an acpidump from a guest system that contains an ACPI0004 node
that you can share?

--
John Baldwin

[Dexuan Cui]

> From: John Baldwin [mailto:j...@freebsd.org]
> Sent: Thursday, April 20, 2017 02:34

> > Can we add the support of "ACPI0004" with the below one-line change?
> >

> > acpi_sysres_probe(device_t dev)
> > {
> > - static char *sysres_ids[] = { "PNP0C01", "PNP0C02", NULL };
> > + static char *sysres_ids[] = { "PNP0C01", "PNP0C02", "ACPI0004", NULL };
> >

> Hmm, so the role of C01 and C02 is to reserve system resources, though we
> in turn allow any child of acpi0 to suballocate those ranges (since historically
> c01 and c02 tend to allocate I/O ranges that are then used by things like the
> EC, PS/2 keyboard controller, etc.). From my reading of ACPI0004 in the ACPI
> 6.1 spec it's not quite clear that ACPI0004 is like that? In particular, it
> seems that 004 should only allow direct children to suballocate? This
> change might work, but it will allow more devices to allocate the ranges in
> _CRS than otherwise.
>
> Do you have an acpidump from a guest system that contains an ACPI0004
> node that you can share?
>

> John Baldwin

Hi John,
Thanks for the help!

Please see the attached file, which is got by
"acpidump -dt | gzip -c9 > acpidump.dt.gz"

In the dump, we can see the "ACPI0004" node (VMOD) is the parent of
"VMBus" (VMBS).
It looks the _CRS of ACPI0004 is dynamically generated. Though we can't
see the length of the MMIO range in the dumped asl code, it does have
a 512MB MMIO range [0xFE0000000, 0xFFFFFFFFF].

It looks FreeBSD can't detect ACPI0004 automatically.
With the above one-line change, I can first find the child device
acpi_sysresource0 of acpi0, then call AcpiWalkResources() to get
the _CRS of acpi_sysresource0, i.e. the 512MB MMIO range.

If you think we shouldn't touch acpi_sysresource0 here, I guess
we can add a new small driver for ACPI0004, just like we added VMBus
driver as a child device of acpi0?

-- Dexuan

[John Baldwin]

Hmmm, so looking at this, the "right" thing is probably to have a device
driver for the ACPI0004 device that parses its _CRS and then allows its
child devices to sub-allocate resources from the ranges in _CRS. However,
this would mean make VMBus be a child of the ACPI0004 device. Suppose
we called the ACPI0004 driver 'acpi_module' then the 'acpi_module0' device
would need to create a child device for all of its child devices. Right
now acpi0 also creates devices for them which is somewhat messy (acpi0
creates child devices anywhere in its namespace that have a valid _HID).
You can find those duplicates and remove them during acpi_module0's attach
routine before creating its own child device_t devices. (We associate
a device_t with each Handle when creating device_t's for ACPI handles
which is how you can find the old device that is a direct child of acpi0
so that it can be removed).

Then when you are the "VMBus" device_t your parent is the ACPI0004 device
so you can easily talk to it to obtain resources (probably ACPI0004 can
just intercept bus_if.m resource methods to manage the resources).

--
John Baldwin

[Sepherosa Ziehau]

The remove/reassociate vmbus part seems kinda "messy" to me. I'd just
hook up a new acpi0004 driver, and let vmbus parse the _CRS like what
we did to the hyper-v's pcib0.

Thanks,
sephe

--
Tomorrow Will Never Die

[John Baldwin]

The acpi_pci driver used to do the remove/reassociate part. What acpi0
should probably be doing is only creating device_t nodes for immediate
children. This would require an ACPI-aware isa0 for LPC devices below
the ISA bus in the ACPI namespace. We haven't done that in part because
BIOS vendors are not always consistent in placing LPC devices under an
ISA bus. However, you otherwise have no good way to find your parent
ACPI0004 device. You could perhaps find your ACPI handle, ask for its
parent handle, then ask for the device_t of that handle to find the
ACPI0004 device, but then you'd need to have all your bus_alloc_resource
calls go to that device, not your "real" parent of acpi0, which means
you can't use any of the standard bus_alloc_resource() methods like
bus_alloc_resource_any() but would have to manually use BUS_ALLOC_RESOURCE
with the ACPI0004 device as the explicit first argument. It is primarily
the ability to let ACPI0004's driver transparently intercept all the
resource allocation so it can manage that is the reason for "VMBus"
to be a child of ACPI0004 rather than its sibling.

--
John Baldwin

[Sepherosa Ziehau]

Well, there could be more then one ACPI0004 typed devices, which could
not form a device tree for vmbus.

Thanks,
sephe

--
Tomorrow Will Never Die

[John Baldwin]

Are you saing a vmbus would need resources from multiple ACPI0004 devices?
That would seem a bit odd. OTOH, if you can have multiple ACPI0004 devices
each with its own VMBus child (in the ACPI namespace) then having the VMBus
be a child of ACPI0004 in new-bus would make it easy to find the "right"
ACPI0004 parent device.

--
John Baldwin

[John Baldwin]

On Sunday, April 30, 2017 09:02:30 AM Sepherosa Ziehau wrote:

> ACPI0004 (and several other PNP ids, see dexuan's submission) is
> something just like the acpi_sysresource. Not directly related to the
> vmbus at all.

In the acpidump, the "vmbus" device was a direct child of ACPI0004. This is
quite different from acpi_sysresource0 which can be in random places in the
namespace (sometimes it is off of isab0, sometimes it is a child of isab0 or
of _SB_), and thus devices that suballocate ranges it reserves (like ipmi0
or acpi_ec0) are sometimes siblings, etc. That doesn't seem to be true for
ACPI004 as it is explicitly described as a container object.

[Sepherosa Ziehau]

On Tue, May 2, 2017 at 11:28 AM, Sepherosa Ziehau <seph...@gmail.com> wrote:

> Thanks for the suggestion. We are reorganizing the tree. The
> original ACPI device (VMBUS) is left as a resource device, instead of
> moving it around.

We have reorganized the vmbus tree:
https://reviews.freebsd.org/D10565

Thanks,
sephe

--
Tomorrow Will Never Die