| Message ID | 20211110053014.489591-5-jusual@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Fix Q35 ACPI PCI Hot-plug I/O issues | expand |
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... > @@ -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)); > } else { > aml_append(dev, aml_name_decl("_HID", aml_eisaid("PNP0A03"))); > } > -- > 2.31.1
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 >
On Wed, Nov 10, 2021 at 2:58 PM Igor Mammedov <imammedo@redhat.com> wrote: > > 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? Lack of support from the original patchset. > > > } else { > > > aml_append(dev, aml_name_decl("_HID", aml_eisaid("PNP0A03"))); > > > } > > > -- > > > 2.31.1 > > >
On Wed, Nov 10, 2021 at 04:25:40PM +0100, Julia Suvorova wrote: > On Wed, Nov 10, 2021 at 2:58 PM Igor Mammedov <imammedo@redhat.com> wrote: > > > > 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? > > Lack of support from the original patchset. Hmm. So PXB will keep using native hotplug. Looks like a good reason to pick up Gerd's patches to fix it up ... > > > > } else { > > > > aml_append(dev, aml_name_decl("_HID", aml_eisaid("PNP0A03"))); > > > > } > > > > -- > > > > 2.31.1 > > > > >
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; method = aml_method("_OSC", 4, AML_NOTSERIALIZED); aml_append(method, aml_create_dword_field(aml_arg(3), aml_int(0), "CDW1")); @@ -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)); 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)); @@ -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)); } else { aml_append(dev, aml_name_decl("_HID", aml_eisaid("PNP0A03"))); }
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(-)