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Re: [PULL v4 44/48] piix4: don't reserve hw resources when hotplug is of
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From: |
Ani Sinha |
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Subject: |
Re: [PULL v4 44/48] piix4: don't reserve hw resources when hotplug is off globally |
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Date: |
Sat, 7 Nov 2020 17:52:02 +0530 |
On Sat, Nov 7, 2020 at 3:40 PM Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
>
> Hi,
>
> On 9/29/20 9:22 AM, Michael S. Tsirkin wrote:
> > From: Ani Sinha <ani@anisinha.ca>
> >
> > When acpi hotplug is turned off for both root pci bus as well as for pci
> > bridges, we should not generate the related ACPI code for DSDT table or
> > initialize related hw ports or reserve hw resources. This change makes
> > sure all those operations are turned off in the case ACPI pci hotplug is
> > off globally.
> >
> > In this change, we also make sure ACPI code for the PCNT method are only
> > added when bsel is enabled for the corresponding pci bus or bridge hotplug
> > is turned on.
>
> I'm trying to understand the following build failure using gcc 9.3.0
> on Ubuntu:
>
> [2567/3684] Compiling C object
> libqemu-x86_64-softmmu.fa.p/hw_i386_acpi-build.c.o
> FAILED: libqemu-x86_64-softmmu.fa.p/hw_i386_acpi-build.c.o
> ../hw/i386/acpi-build.c: In function 'build_append_pci_bus_devices':
> ../hw/i386/acpi-build.c:496:9: error: 'method' may be used uninitialized
> in this function [-Werror=maybe-uninitialized]
> 496 | aml_append(parent_scope, method);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
>
> >
> > As q35 machines do not use bsel for it's pci buses at this point in time,
> > this
> > change affects DSDT acpi table for q35 machines as well. Therefore, we will
> > also need to commit the updated golden master DSDT table acpi binary blobs
> > as
> > well. Following is the list of blobs which needs updating:
> >
> > tests/data/acpi/q35/DSDT
> > tests/data/acpi/q35/DSDT.acpihmat
> > tests/data/acpi/q35/DSDT.bridge
> > tests/data/acpi/q35/DSDT.cphp
> > tests/data/acpi/q35/DSDT.dimmpxm
> > tests/data/acpi/q35/DSDT.ipmibt
> > tests/data/acpi/q35/DSDT.memhp
> > tests/data/acpi/q35/DSDT.mmio64
> > tests/data/acpi/q35/DSDT.numamem
> > tests/data/acpi/q35/DSDT.tis
> >
> > These tables are updated in the following commit. Without the updated table
> > blobs, the unit tests would fail with this patch.
> >
> > Signed-off-by: Ani Sinha <ani@anisinha.ca>
> > Reviewed-by: Igor Mammedov <imammedo@redhat.com>
> > Message-Id: <20200918084111.15339-11-ani@anisinha.ca>
> > Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> > hw/acpi/piix4.c | 6 ++++--
> > hw/i386/acpi-build.c | 25 ++++++++++++++++++-------
> > 2 files changed, 22 insertions(+), 9 deletions(-)
> >
> > diff --git a/hw/acpi/piix4.c b/hw/acpi/piix4.c
> > index 832f8fba82..894d357f8c 100644
> > --- a/hw/acpi/piix4.c
> > +++ b/hw/acpi/piix4.c
> > @@ -596,8 +596,10 @@ static void
> > piix4_acpi_system_hot_add_init(MemoryRegion *parent,
> > "acpi-gpe0", GPE_LEN);
> > memory_region_add_subregion(parent, GPE_BASE, &s->io_gpe);
> >
> > - acpi_pcihp_init(OBJECT(s), &s->acpi_pci_hotplug, bus, parent,
> > - s->use_acpi_hotplug_bridge);
> > + if (s->use_acpi_hotplug_bridge || s->use_acpi_root_pci_hotplug) {
> > + acpi_pcihp_init(OBJECT(s), &s->acpi_pci_hotplug, bus, parent,
> > + s->use_acpi_hotplug_bridge);
> > + }
> >
> > s->cpu_hotplug_legacy = true;
> > object_property_add_bool(OBJECT(s), "cpu-hotplug-legacy",
> > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> > index 2b17843837..8d14e4667a 100644
> > --- a/hw/i386/acpi-build.c
> > +++ b/hw/i386/acpi-build.c
> > @@ -96,6 +96,7 @@ typedef struct AcpiPmInfo {
> > bool s4_disabled;
> > bool pcihp_bridge_en;
> > bool smi_on_cpuhp;
> > + bool pcihp_root_en;
> > uint8_t s4_val;
> > AcpiFadtData fadt;
> > uint16_t cpu_hp_io_base;
> > @@ -251,6 +252,9 @@ static void acpi_get_pm_info(MachineState *machine,
> > AcpiPmInfo *pm)
> > pm->pcihp_bridge_en =
> > object_property_get_bool(obj,
> > "acpi-pci-hotplug-with-bridge-support",
> > NULL);
> > + pm->pcihp_root_en =
> > + object_property_get_bool(obj, "acpi-root-pci-hotplug",
> > + NULL);
> > }
> >
> > static void acpi_get_misc_info(AcpiMiscInfo *info)
> > @@ -456,10 +460,12 @@ static void build_append_pci_bus_devices(Aml
> > *parent_scope, PCIBus *bus,
> > }
> >
> > /* Append PCNT method to notify about events on local and child buses.
> > - * Add unconditionally for root since DSDT expects it.
> > + * Add this method for root bus only when hotplug is enabled since DSDT
> > + * expects it.
> > */
> > - method = aml_method("PCNT", 0, AML_NOTSERIALIZED);
> > -
> > + if (bsel || pcihp_bridge_en) {
> > + method = aml_method("PCNT", 0, AML_NOTSERIALIZED);
> > + }
>
> build_append_pci_bus_devices() is not easy to follow and could certainly
> benefit from a refactor.
Hmm, ok will do that in my spare time.
>
> So here, before 'method' was always reinitialized. Now not always,
> so it can be any value set in the big for() loop before...
In line 467 above, method is initialized when bsel is available or
pcihp is enabled. In line 496, it is appended to the parent scope only
under those conditions as well. Basically, in hunks
+ if (bsel || pcihp_bridge_en) {
+ method = aml_method("PCNT", 0, AML_NOTSERIALIZED);
+ }
and
+
+ if (bsel || pcihp_bridge_en) {
+ aml_append(parent_scope, method);
+ }
the conditions are exactly the same.
Hence, I see no contradiction. To satisfy the compiler, one could do this:
diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 4f66642..79b86d4 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -349,7 +349,7 @@ static void build_append_pcihp_notify_entry(Aml
*method, int slot)
static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus,
bool pcihp_bridge_en)
{
- Aml *dev, *notify_method = NULL, *method;
+ Aml *dev, *notify_method = NULL, *method = NULL;
QObject *bsel;
PCIBus *sec;
int i;
@@ -492,7 +492,7 @@ static void build_append_pci_bus_devices(Aml
*parent_scope, PCIBus *bus,
}
}
- if (bsel || pcihp_bridge_en) {
+ if (method) {
aml_append(parent_scope, method);
}
qobject_unref(bsel);
>
> Something is definitively wrong.
>
> > /* If bus supports hotplug select it and notify about local events */
> > if (bsel) {
> > uint64_t bsel_val = qnum_get_uint(qobject_to(QNum, bsel));
> > @@ -485,7 +491,10 @@ static void build_append_pci_bus_devices(Aml
> > *parent_scope, PCIBus *bus,
> > aml_append(method, aml_name("^S%.02X.PCNT", devfn));
> > }
> > }
> > - aml_append(parent_scope, method);
> > +
> > + if (bsel || pcihp_bridge_en) {
> > + aml_append(parent_scope, method);
> > + }
> > qobject_unref(bsel);
> > }
> >
> > @@ -1510,7 +1519,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
> > build_hpet_aml(dsdt);
> > build_piix4_isa_bridge(dsdt);
> > build_isa_devices_aml(dsdt);
> > - build_piix4_pci_hotplug(dsdt);
> > + if (pm->pcihp_bridge_en || pm->pcihp_root_en) {
> > + build_piix4_pci_hotplug(dsdt);
> > + }
> > build_piix4_pci0_int(dsdt);
> > } else {
> > sb_scope = aml_scope("_SB");
> > @@ -1579,7 +1590,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
> > {
> > aml_append(scope, aml_name_decl("_HID", aml_string("ACPI0006")));
> >
> > - if (misc->is_piix4) {
> > + if (misc->is_piix4 && (pm->pcihp_bridge_en || pm->pcihp_root_en)) {
> > method = aml_method("_E01", 0, AML_NOTSERIALIZED);
> > aml_append(method,
> > aml_acquire(aml_name("\\_SB.PCI0.BLCK"), 0xFFFF));
> > @@ -1731,7 +1742,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
> > crs_range_set_free(&crs_range_set);
> >
> > /* reserve PCIHP resources */
> > - if (pm->pcihp_io_len) {
> > + if (pm->pcihp_io_len && (pm->pcihp_bridge_en || pm->pcihp_root_en)) {
> > dev = aml_device("PHPR");
> > aml_append(dev, aml_name_decl("_HID", aml_string("PNP0A06")));
> > aml_append(dev,
> >
>