From 37308e60d43323c0ea65d734487ce6542f8a9d3b Mon Sep 17 00:00:00 2001
From: Eric Auger <eric.auger@redhat.com>
Date: Tue, 5 Oct 2021 10:53:12 +0200
Subject: [PATCH] hw/pci-host/gpex: [needs kernel fix] Allow to generate
 preserve boot config DSM #5

Add a 'preserve_config' field in struct GPEXConfig and
if set, generate the DSM #5 for preserving PCI boot configurations.
The DSM presence is needed to expose RMRs.

At the moment the DSM generation is not yet enabled.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
---
 hw/pci-host/gpex-acpi.c    | 35 +++++++++++++++++++++++++++++++----
 include/hw/pci-host/gpex.h |  1 +
 2 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/hw/pci-host/gpex-acpi.c b/hw/pci-host/gpex-acpi.c
index ac5d229757..ce424fc9da 100644
--- a/hw/pci-host/gpex-acpi.c
+++ b/hw/pci-host/gpex-acpi.c
@@ -49,9 +49,10 @@ static void acpi_dsdt_add_pci_route_table(Aml *dev, uint32_t irq)
     }
 }
 
-static void acpi_dsdt_add_pci_osc(Aml *dev)
+static void acpi_dsdt_add_pci_osc(Aml *dev, bool preserve_config)
 {
     Aml *method, *UUID, *ifctx, *ifctx1, *elsectx, *buf;
+    uint8_t byte_list[1] = {0};
 
     /* Declare an _OSC (OS Control Handoff) method */
     aml_append(dev, aml_name_decl("SUPP", aml_int(0)));
@@ -113,10 +114,24 @@ static void acpi_dsdt_add_pci_osc(Aml *dev)
     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 for functions other than function 0 and 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;
@@ -174,6 +189,12 @@ void acpi_dsdt_add_gpex(Aml *scope, struct GPEXConfig *cfg)
                 aml_append(dev, aml_name_decl("_PXM", aml_int(numa_node)));
             }
 
+            if (cfg->preserve_config) {
+                method = aml_method("_DSM", 5, AML_SERIALIZED);
+                aml_append(method, aml_return(aml_int(0)));
+                aml_append(dev, method);
+            }
+
             acpi_dsdt_add_pci_route_table(dev, cfg->irq);
 
             /*
@@ -188,7 +209,7 @@ void acpi_dsdt_add_gpex(Aml *scope, struct GPEXConfig *cfg)
             if (is_cxl) {
                 build_cxl_osc_method(dev);
             } else {
-                acpi_dsdt_add_pci_osc(dev);
+                acpi_dsdt_add_pci_osc(dev, cfg->preserve_config);
             }
 
             aml_append(scope, dev);
@@ -205,6 +226,12 @@ void acpi_dsdt_add_gpex(Aml *scope, struct GPEXConfig *cfg)
     aml_append(dev, aml_name_decl("_STR", aml_unicode("PCIe 0 Device")));
     aml_append(dev, aml_name_decl("_CCA", aml_int(1)));
 
+    if (cfg->preserve_config) {
+        method = aml_method("_DSM", 5, AML_SERIALIZED);
+        aml_append(method, aml_return(aml_int(0)));
+        aml_append(dev, method);
+    }
+
     acpi_dsdt_add_pci_route_table(dev, cfg->irq);
 
     method = aml_method("_CBA", 0, AML_NOTSERIALIZED);
@@ -263,7 +290,7 @@ void acpi_dsdt_add_gpex(Aml *scope, struct GPEXConfig *cfg)
     }
     aml_append(dev, aml_name_decl("_CRS", rbuf));
 
-    acpi_dsdt_add_pci_osc(dev);
+    acpi_dsdt_add_pci_osc(dev, 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 b0240bd768..65475f7f9d 100644
--- a/include/hw/pci-host/gpex.h
+++ b/include/hw/pci-host/gpex.h
@@ -64,6 +64,7 @@ struct GPEXConfig {
     MemMapEntry pio;
     int         irq;
     PCIBus      *bus;
+    bool        preserve_config;
 };
 
 int gpex_set_irq_num(GPEXHost *s, int index, int gsi);
-- 
2.41.0.windows.1