From: Eric Auger Date: Thu, 29 Jan 2026 13:32:05 +0000 (+0000) Subject: hw/pci-host/gpex: Allow to generate preserve boot config DSM #5 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=59a5c80623abbb7f5f52fc227cfe0c142858858c;p=thirdparty%2Fqemu.git hw/pci-host/gpex: Allow to generate preserve boot config DSM #5 Add a 'preserve_config' field in struct GPEXConfig and, if set, generate the _DSM function #5 for preserving PCI boot configurations. This will be used for SMMUv3 accel=on support in subsequent patch. When SMMUv3 acceleration (accel=on) is enabled, QEMU exposes IORT Reserved Memory Region (RMR) nodes to support MSI doorbell translations. As per the Arm IORT specification, using IORT RMRs mandates the presence of _DSM function #5 so that the OS retains the firmware-assigned PCI configuration. Hence, this patch adds conditional support for generating _DSM #5. According to the ACPI Specification, Revision 6.6, Section 9.1.1 - “_DSM (Device Specific Method)”, " If Function Index is zero, the return is a buffer containing one bit for each function index, starting with zero. Bit 0 indicates whether there is support for any functions other than function 0 for the specified UUID and Revision ID. If set to zero, no functions are supported (other than function zero) for the specified UUID and Revision ID. If set to one, at least one additional function is supported. For all other bits in the buffer, a bit is set to zero to indicate if that function index is not supported for the specific UUID and Revision ID. (For example, bit 1 set to 0 indicates that function index 1 is not supported for the specific UUID and Revision ID.) " Please refer PCI Firmware Specification, Revision 3.3, Section 4.6.5 — "_DSM for Preserving PCI Boot Configurations" for Function 5 of _DSM method. Also, while at it, move the byte_list declaration to the top of the function for clarity. At the moment, DSM generation is not yet enabled. The resulting AML when preserve_config=true is: Method (_DSM, 4, NotSerialized) { If ((Arg0 == ToUUID ("e5c937d0-3553-4d7a-9117-ea4d19c3434d"))) { If ((Arg2 == Zero)) { Return (Buffer (One) { 0x21 }) } If ((Arg2 == 0x05)) { Return (Zero) } } ... } Cc: Michael S. Tsirkin Signed-off-by: Eric Auger Signed-off-by: Shameer Kolothum Signed-off-by: Shameer Kolothum Tested-by: Zhangfei Gao Tested-by: Eric Auger Reviewed-by: Jonathan Cameron Reviewed-by: Michael S. Tsirkin Message-id: 20260126104342.253965-23-skolothumtho@nvidia.com [Shameer: Removed possible duplicate _DSM creations] Signed-off-by: Shameer Kolothum Tested-by: Zhangfei Gao Reviewed-by: Jonathan Cameron Reviewed-by: Michael S. Tsirkin Tested-by: Eric Auger Signed-off-by: Shameer Kolothum Signed-off-by: Peter Maydell --- diff --git a/hw/pci-host/gpex-acpi.c b/hw/pci-host/gpex-acpi.c index 4587baeb78..d9820f9b41 100644 --- a/hw/pci-host/gpex-acpi.c +++ b/hw/pci-host/gpex-acpi.c @@ -51,10 +51,11 @@ static void acpi_dsdt_add_pci_route_table(Aml *dev, uint32_t irq, } } -static Aml *build_pci_host_bridge_dsm_method(void) +static Aml *build_pci_host_bridge_dsm_method(bool preserve_config) { Aml *method = aml_method("_DSM", 4, AML_NOTSERIALIZED); Aml *UUID, *ifctx, *ifctx1, *buf; + uint8_t byte_list[1] = {0}; /* PCI Firmware Specification 3.0 * 4.6.1. _DSM for PCI Express Slot Information @@ -64,10 +65,23 @@ static Aml *build_pci_host_bridge_dsm_method(void) UUID = aml_touuid("E5C937D0-3553-4D7A-9117-EA4D19C3434D"); ifctx = aml_if(aml_equal(aml_arg(0), UUID)); ifctx1 = aml_if(aml_equal(aml_arg(2), aml_int(0))); - uint8_t byte_list[1] = {0}; + if (preserve_config) { + /* support functions other than 0, specifically function 5 */ + byte_list[0] = 0x21; + } buf = aml_buffer(1, byte_list); aml_append(ifctx1, aml_return(buf)); aml_append(ifctx, ifctx1); + if (preserve_config) { + Aml *ifctx2 = aml_if(aml_equal(aml_arg(2), aml_int(5))); + /* + * 0 - The operating system must not ignore the PCI configuration that + * firmware has done at boot time. + */ + aml_append(ifctx2, aml_return(aml_int(0))); + aml_append(ifctx, ifctx2); + } + aml_append(method, ifctx); byte_list[0] = 0; @@ -77,12 +91,13 @@ static Aml *build_pci_host_bridge_dsm_method(void) } static void acpi_dsdt_add_host_bridge_methods(Aml *dev, - bool enable_native_pcie_hotplug) + bool enable_native_pcie_hotplug, + bool preserve_config) { /* Declare an _OSC (OS Control Handoff) method */ aml_append(dev, build_pci_host_bridge_osc_method(enable_native_pcie_hotplug)); - aml_append(dev, build_pci_host_bridge_dsm_method()); + aml_append(dev, build_pci_host_bridge_dsm_method(preserve_config)); } void acpi_dsdt_add_gpex(Aml *scope, struct GPEXConfig *cfg) @@ -152,7 +167,8 @@ void acpi_dsdt_add_gpex(Aml *scope, struct GPEXConfig *cfg) build_cxl_osc_method(dev); } else { /* pxb bridges do not have ACPI PCI Hot-plug enabled */ - acpi_dsdt_add_host_bridge_methods(dev, true); + acpi_dsdt_add_host_bridge_methods(dev, true, + cfg->preserve_config); } aml_append(scope, dev); @@ -227,7 +243,8 @@ void acpi_dsdt_add_gpex(Aml *scope, struct GPEXConfig *cfg) } aml_append(dev, aml_name_decl("_CRS", rbuf)); - acpi_dsdt_add_host_bridge_methods(dev, cfg->pci_native_hotplug); + acpi_dsdt_add_host_bridge_methods(dev, cfg->pci_native_hotplug, + cfg->preserve_config); Aml *dev_res0 = aml_device("%s", "RES0"); aml_append(dev_res0, aml_name_decl("_HID", aml_string("PNP0C02"))); diff --git a/include/hw/pci-host/gpex.h b/include/hw/pci-host/gpex.h index 695886dedd..1da9c85bce 100644 --- a/include/hw/pci-host/gpex.h +++ b/include/hw/pci-host/gpex.h @@ -46,6 +46,7 @@ struct GPEXConfig { int irq; PCIBus *bus; bool pci_native_hotplug; + bool preserve_config; }; typedef struct GPEXIrq GPEXIrq;