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Re: [PATCH 4/5] hw/i386/acpi-build: Deny control on PCIe Native Hot-plug
From: |
Igor Mammedov |
Subject: |
Re: [PATCH 4/5] hw/i386/acpi-build: Deny control on PCIe Native Hot-plug in _OSC |
Date: |
Wed, 10 Nov 2021 14:57:59 +0100 |
On Wed, 10 Nov 2021 02:21:34 -0500
"Michael S. Tsirkin" <mst@redhat.com> wrote:
> On Wed, Nov 10, 2021 at 06:30:13AM +0100, Julia Suvorova wrote:
> > There are two ways to enable ACPI PCI Hot-plug:
> >
> > * Disable the Hot-plug Capable bit on PCIe slots.
> >
> > This was the first approach which led to regression [1-2], as
> > I/O space for a port is allocated only when it is hot-pluggable,
> > which is determined by HPC bit.
> >
> > * Leave the HPC bit on and disable PCIe Native Hot-plug in _OSC
> > method.
> >
> > This removes the (future) ability of hot-plugging switches with PCIe
> > Native hotplug since ACPI PCI Hot-plug only works with cold-plugged
> > bridges. If the user wants to explicitely use this feature, they can
> > disable ACPI PCI Hot-plug with:
> > --global ICH9-LPC.acpi-pci-hotplug-with-bridge-support=off
> >
> > Change the bit in _OSC method so that the OS selects ACPI PCI Hot-plug
> > instead of PCIe Native.
> >
> > [1] https://gitlab.com/qemu-project/qemu/-/issues/641
> > [2] https://bugzilla.redhat.com/show_bug.cgi?id=2006409
> >
> > Signed-off-by: Julia Suvorova <jusual@redhat.com>
> > ---
> > hw/i386/acpi-build.c | 12 ++++++++----
> > 1 file changed, 8 insertions(+), 4 deletions(-)
> >
> > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> > index a3ad6abd33..a2f92ab32b 100644
> > --- a/hw/i386/acpi-build.c
> > +++ b/hw/i386/acpi-build.c
> > @@ -1337,7 +1337,7 @@ static void build_x86_acpi_pci_hotplug(Aml *table,
> > uint64_t pcihp_addr)
> > aml_append(table, scope);
> > }
> >
> > -static Aml *build_q35_osc_method(void)
> > +static Aml *build_q35_osc_method(bool acpi_pcihp)
> > {
> > Aml *if_ctx;
> > Aml *if_ctx2;
> > @@ -1345,6 +1345,7 @@ static Aml *build_q35_osc_method(void)
> > Aml *method;
> > Aml *a_cwd1 = aml_name("CDW1");
> > Aml *a_ctrl = aml_local(0);
> > + const uint64_t hotplug = acpi_pcihp ? 0x1E : 0x1F;
>
> drop this variable and open-code at use point below.
> As it is the comment is misplaced.
> Also a slightly better way to write this:
> 0x1E | (acpi_pcihp ? 0x0 : 0x1)
>
>
>
> >
> > method = aml_method("_OSC", 4, AML_NOTSERIALIZED);
> > aml_append(method, aml_create_dword_field(aml_arg(3), aml_int(0),
> > "CDW1"));
>
> So what acpi_pcihp does is enable/disable native pcie hotplug.
> How about we call the option exactly that?
>
>
> > @@ -1359,8 +1360,9 @@ static Aml *build_q35_osc_method(void)
> > /*
> > * Always allow native PME, AER (no dependencies)
> > * Allow SHPC (PCI bridges can have SHPC controller)
> > + * Disable PCIe Native Hot-plug if ACPI PCI Hot-plug is enabled.
> > */
> > - aml_append(if_ctx, aml_and(a_ctrl, aml_int(0x1F), a_ctrl));
> > + aml_append(if_ctx, aml_and(a_ctrl, aml_int(hotplug), a_ctrl));
> >
>
> using the variable hotplug just made things confusing,
> open-coding will be clearer.
>
>
> > if_ctx2 = aml_if(aml_lnot(aml_equal(aml_arg(1), aml_int(1))));
> > /* Unknown revision */
> > @@ -1449,7 +1451,7 @@ 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(pcmc->pci_root_uid)));
> > - aml_append(dev, build_q35_osc_method());
> > + aml_append(dev, build_q35_osc_method(pm->pcihp_bridge_en));
> > aml_append(sb_scope, dev);
> > if (mcfg_valid) {
> > aml_append(sb_scope, build_q35_dram_controller(&mcfg));
>
> One of the complaints of libvirt people was that the
> name is confusing. It seems to say whether to describe bridges
> in ACPI but it also disables native hotplug, but only for PCIe.
>
> Maybe we should address this with flags saying whether to enable each of
> acpi,pcie,shpc hotplug separately...
yep, mask with field defines would be better,
but I'd hold off such change to post 6.2 time.
>
> > @@ -1565,7 +1567,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
> > if (pci_bus_is_express(bus)) {
> > aml_append(dev, aml_name_decl("_HID",
> > aml_eisaid("PNP0A08")));
> > aml_append(dev, aml_name_decl("_CID",
> > aml_eisaid("PNP0A03")));
> > - aml_append(dev, build_q35_osc_method());
> > + /* Expander bridges do not have ACPI PCI Hot-plug enabled
> > */
> > + aml_append(dev, build_q35_osc_method(false));
this's it not obvious, why PXBs aren't capable of ACPI PCI Hot-plug?
> > } else {
> > aml_append(dev, aml_name_decl("_HID",
> > aml_eisaid("PNP0A03")));
> > }
> > --
> > 2.31.1
>
- Re: [PATCH 1/5] hw/pci/pcie_port: Rename 'native-hotplug' to 'native-hpc-bit', (continued)
[PATCH 2/5] hw/acpi/ich9: Add compatibility option for 'native-hpc-bit', Julia Suvorova, 2021/11/10
[PATCH 3/5] bios-tables-test: Allow changes in DSDT ACPI tables, Julia Suvorova, 2021/11/10
[PATCH 4/5] hw/i386/acpi-build: Deny control on PCIe Native Hot-plug in _OSC, Julia Suvorova, 2021/11/10
[PATCH 5/5] bios-tables-test: Update golden binaries, Julia Suvorova, 2021/11/10