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Re: [Qemu-devel] [PATCH V3] hw/pxb-pcie: fix PCI Express hotplug support
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH V3] hw/pxb-pcie: fix PCI Express hotplug support |
Date: |
Mon, 27 Feb 2017 22:57:17 +0200 |
On Mon, Feb 27, 2017 at 03:12:26PM +0200, Marcel Apfelbaum wrote:
> Add the missing osc method for pxb-pcie devices as APCI spec recommends,
> see 6.2.10.3 OSC Implementation Example for PCI Host Bridge Devices, ACPI 5.0:
>
> It is recommended that a machine with multiple host bridge devices
> should report the same capabilities for all host bridges, and also
> negotiate control of the features described in the Control Field in
> the same way for all host bridges.
>
> Reviewed-by: Igor Mammedov <address@hidden>
> Signed-off-by: Marcel Apfelbaum <address@hidden>
> ---
>
> Note to maintainer:
> Please update ACPI test files.
>
> V2 -> V3:
> - Modified comment (Igor)
>
> V1 -> V2:
> Addressed Michael S. Tsirkin's comments:
> - Added documentation to q35 osc function
> - Made _osc serialized. I did not add compat property
> since it seems guest OSs do not care anyway about the OSC
> being serialized.
> - Kept the SUPP field even if is not used and also
> left both SUPP and CTRL out of the _osc because all
> systems I checked and the ACPI spec keep them that way,
> maybe is some kind of documentation contract.
>
> Thanks,
> Marcel
>
>
> hw/i386/acpi-build.c | 41 +++++++++++++++++++++++++++++++++++------
> 1 file changed, 35 insertions(+), 6 deletions(-)
>
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index 1c928ab..ad3f233 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -1796,7 +1796,7 @@ static void build_piix4_pci_hotplug(Aml *table)
> aml_append(table, scope);
> }
>
> -static Aml *build_q35_osc_method(void)
> +static void build_q35_osc_method(Aml *dev)
This does more than just build _OSC so please
give it a better name.
> {
> Aml *if_ctx;
> Aml *if_ctx2;
> @@ -1805,7 +1805,35 @@ static Aml *build_q35_osc_method(void)
> Aml *a_cwd1 = aml_name("CDW1");
> Aml *a_ctrl = aml_name("CTRL");
>
> - method = aml_method("_OSC", 4, AML_NOTSERIALIZED);
> + /*
> + * Bits defined in the Support Field provide information
> + * regarding OS supported features.
> + *
> + * This field is not actually used and can be removed,
> + * however it appears even if unused on most DSDTs.
What does this mean? Our _OSC method uses these,
that's why we have them. How can you just remove them?
I think you mean we could remove the code writing to it.
I don't think keeping it around is justified.
Same applies to CTRL btw. We could use a local variable
instead.
> + *
> + * See:
> + * Table 6-148 Interpretation of _OSC Support Field,
> + * Passed in via the 2nd dword in Arg3, APCI 5.0
Why 5.0? This is not how we do it. Pls find the earliest spec version
that has this. 3.0?
> + */
> + aml_append(dev, aml_name_decl("SUPP", aml_int(0)));
> +
> + /*
> + * Bits defined in the Control Field are used to submit
> + * request by the OS for control/handling of the associated feature
> + *
> + * See: Table 6-149 Interpretation of _OSC Control Field,
> + * Passed in via Arg3, ACPI 5.0
> + * Table 6-150 Interpretation of _OSC Control Field,
> + * Returned Value, APCI 5.0
> + */
> + aml_append(dev, aml_name_decl("CTRL", aml_int(0)));
> +
> +
> + /*
> + * 6.2.10 _OSC (Operating System Capabilities), APCI 5.0
> + */
Same here.
> + method = aml_method("_OSC", 4, AML_SERIALIZED);
> aml_append(method, aml_create_dword_field(aml_arg(3), aml_int(0),
> "CDW1"));
>
> if_ctx = aml_if(aml_equal(
> @@ -1842,7 +1870,7 @@ static Aml *build_q35_osc_method(void)
> aml_append(method, else_ctx);
>
> aml_append(method, aml_return(aml_arg(3)));
> - return method;
> + aml_append(dev, method);
If you drop SUPP and CTRL then you can keep it simple, right?
> }
>
> static void
> @@ -1898,9 +1926,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
> aml_append(dev, aml_name_decl("_CID", aml_eisaid("PNP0A03")));
> aml_append(dev, aml_name_decl("_ADR", aml_int(0)));
> aml_append(dev, aml_name_decl("_UID", aml_int(1)));
> - aml_append(dev, aml_name_decl("SUPP", aml_int(0)));
> - aml_append(dev, aml_name_decl("CTRL", aml_int(0)));
> - aml_append(dev, build_q35_osc_method());
> + build_q35_osc_method(dev);
> aml_append(sb_scope, dev);
> aml_append(dsdt, sb_scope);
>
> @@ -1964,6 +1990,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
> aml_append(dev, aml_name_decl("_UID", aml_int(bus_num)));
> aml_append(dev, aml_name_decl("_HID", aml_eisaid("PNP0A03")));
> aml_append(dev, aml_name_decl("_BBN", aml_int(bus_num)));
> + if (pci_bus_is_express(bus)) {
> + build_q35_osc_method(dev);
> + }
>
> if (numa_node != NUMA_NODE_UNASSIGNED) {
> aml_append(dev, aml_name_decl("_PXM", aml_int(numa_node)));
> --
> 2.5.5
so how about
--->
acpi: simplify _OSC
Our _OSC method has a bunch of unused code loading data
into external CTRL and SUPP fields which are then never
used. Drop this in favor of a single local variable.
Signed-off-by: Michael S. Tsirkin <address@hidden>
---
diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index db04cf5..efbbfcb 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -1804,7 +1804,7 @@ static Aml *build_q35_osc_method(void)
Aml *else_ctx;
Aml *method;
Aml *a_cwd1 = aml_name("CDW1");
- Aml *a_ctrl = aml_name("CTRL");
+ Aml *a_ctrl = aml_local(0);
method = aml_method("_OSC", 4, AML_NOTSERIALIZED);
aml_append(method, aml_create_dword_field(aml_arg(3), aml_int(0), "CDW1"));
@@ -1814,7 +1814,6 @@ static Aml *build_q35_osc_method(void)
aml_append(if_ctx, aml_create_dword_field(aml_arg(3), aml_int(4), "CDW2"));
aml_append(if_ctx, aml_create_dword_field(aml_arg(3), aml_int(8), "CDW3"));
- aml_append(if_ctx, aml_store(aml_name("CDW2"), aml_name("SUPP")));
aml_append(if_ctx, aml_store(aml_name("CDW3"), a_ctrl));
/*
@@ -1899,8 +1898,6 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
aml_append(dev, aml_name_decl("_CID", aml_eisaid("PNP0A03")));
aml_append(dev, aml_name_decl("_ADR", aml_int(0)));
aml_append(dev, aml_name_decl("_UID", aml_int(1)));
- aml_append(dev, aml_name_decl("SUPP", aml_int(0)));
- aml_append(dev, aml_name_decl("CTRL", aml_int(0)));
aml_append(dev, build_q35_osc_method());
aml_append(sb_scope, dev);
aml_append(dsdt, sb_scope);