[PATCH v5 7/9] hw/i386/acpi-build: Add DMAR support to bypass iommu

[Wang Xingang]

From: Xingang Wang <wangxingang5@huawei.com>

In DMAR table, the drhd is set to cover all PCI devices when intel_iommu
is on. To support bypass iommu feature, we need to walk the PCI bus with
bypass_iommu disabled and add explicit scope data in DMAR drhd structure.

/mnt/sdb/wxg/qemu-next/qemu/build/x86_64-softmmu/qemu-system-x86_64 \
 -machine q35,accel=kvm,default_bus_bypass_iommu=true \
 -cpu host \
 -m 16G \
 -smp 36,sockets=2,cores=18,threads=1 \
 -device pxb-pcie,bus_nr=0x10,id=pci.10,bus=pcie.0,addr=0x3 \
 -device pxb-pcie,bus_nr=0x20,id=pci.20,bus=pcie.0,addr=0x4,bypass_iommu=true \
 -device pcie-root-port,port=0x1,chassis=1,id=pci.11,bus=pci.10,addr=0x0 \
 -device pcie-root-port,port=0x2,chassis=2,id=pci.21,bus=pci.20,addr=0x0 \
 -device virtio-scsi-pci,id=scsi0,bus=pci.11,addr=0x0 \
 -device virtio-scsi-pci,id=scsi1,bus=pci.21,addr=0x0 \
 -drive 
file=/mnt/sdb/wxg/fedora-48g.qcow2,format=qcow2,if=none,id=drive-scsi0-0-0-0,cache=none,aio=native
 \
 -device 
scsi-hd,bus=scsi1.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0-0-0-0,id=scsi0-0-0-0,bootindex=1
 \
 -device intel-iommu \
 -nographic \

And we get the guest configuration:

~ lspci -vt
-+-[0000:20]---00.0-[21]----00.0  Red Hat, Inc. Virtio SCSI
 +-[0000:10]---00.0-[11]----00.0  Red Hat, Inc. Virtio SCSI
 \-[0000:00]-+-00.0  Intel Corporation 82G33/G31/P35/P31 Express DRAM Controller
             +-01.0  Device 1234:1111
             +-02.0  Intel Corporation 82574L Gigabit Network Connection
             +-03.0  Red Hat, Inc. QEMU PCIe Expander bridge
             +-04.0  Red Hat, Inc. QEMU PCIe Expander bridge
             +-1f.0  Intel Corporation 82801IB (ICH9) LPC Interface Controller
             +-1f.2  Intel Corporation 82801IR/IO/IH (ICH9R/DO/DH) 6 port SATA 
Controller [AHCI mode]
             \-1f.3  Intel Corporation 82801I (ICH9 Family) SMBus Controller

With bypass_iommu enabled on root bus, the attached devices will bypass iommu:

/sys/class/iommu/dmar0
├── devices
│   ├── 0000:10:00.0 -> ../../../../pci0000:10/0000:10:00.0
│   └── 0000:11:00.0 -> ../../../../pci0000:10/0000:10:00.0/0000:11:00.0

Signed-off-by: Xingang Wang <wangxingang5@huawei.com>
---
 hw/i386/acpi-build.c | 68 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 66 insertions(+), 2 deletions(-)

diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 796ffc6f5c..1b972b4913 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -2005,6 +2005,56 @@ build_srat(GArray *table_data, BIOSLinker *linker, 
MachineState *machine)
                  x86ms->oem_table_id);
 }
 
+/*
+ * Insert DMAR scope for PCI bridges and endpoint devcie
+ */
+static void
+insert_scope(PCIBus *bus, PCIDevice *dev, void *opaque)
+{
+    GArray *scope_blob = opaque;
+    AcpiDmarDeviceScope *scope = NULL;
+
+    if (object_dynamic_cast(OBJECT(dev), TYPE_PCI_BRIDGE)) {
+        /* Dmar Scope Type: 0x02 for PCI Bridge */
+        build_append_int_noprefix(scope_blob, 0x02, 1);
+    } else {
+        /* Dmar Scope Type: 0x01 for PCI Endpoint Device */
+        build_append_int_noprefix(scope_blob, 0x01, 1);
+    }
+
+    /* length */
+    build_append_int_noprefix(scope_blob,
+                              sizeof(*scope) + sizeof(scope->path[0]), 1);
+    /* reserved */
+    build_append_int_noprefix(scope_blob, 0, 2);
+    /* enumeration_id */
+    build_append_int_noprefix(scope_blob, 0, 1);
+    /* bus */
+    build_append_int_noprefix(scope_blob, pci_bus_num(bus), 1);
+    /* device */
+    build_append_int_noprefix(scope_blob, PCI_SLOT(dev->devfn), 1);
+    /* function */
+    build_append_int_noprefix(scope_blob, PCI_FUNC(dev->devfn), 1);
+}
+
+/* For a given PCI host bridge, walk and insert DMAR scope */
+static int
+dmar_host_bridges(Object *obj, void *opaque)
+{
+    GArray *scope_blob = opaque;
+
+    if (object_dynamic_cast(obj, TYPE_PCI_HOST_BRIDGE)) {
+        PCIBus *bus = PCI_HOST_BRIDGE(obj)->bus;
+
+        if (bus && !pci_bus_bypass_iommu(bus)) {
+            pci_for_each_device(bus, pci_bus_num(bus), insert_scope,
+                                scope_blob);
+        }
+    }
+
+    return 0;
+}
+
 /*
  * VT-d spec 8.1 DMA Remapping Reporting Structure
  * (version Oct. 2014 or later)
@@ -2024,6 +2074,15 @@ build_dmar_q35(GArray *table_data, BIOSLinker *linker, 
const char *oem_id,
     /* Root complex IOAPIC use one path[0] only */
     size_t ioapic_scope_size = sizeof(*scope) + sizeof(scope->path[0]);
     IntelIOMMUState *intel_iommu = INTEL_IOMMU_DEVICE(iommu);
+    GArray *scope_blob = g_array_new(false, true, 1);
+
+    /*
+     * A PCI bus walk, for each PCI host bridge.
+     * Insert scope for each PCI bridge and endpoint device which
+     * is attached to a bus with iommu enabled.
+     */
+    object_child_foreach_recursive(object_get_root(),
+                                   dmar_host_bridges, scope_blob);
 
     assert(iommu);
     if (x86_iommu_ir_supported(iommu)) {
@@ -2037,8 +2096,9 @@ build_dmar_q35(GArray *table_data, BIOSLinker *linker, 
const char *oem_id,
     /* DMAR Remapping Hardware Unit Definition structure */
     drhd = acpi_data_push(table_data, sizeof(*drhd) + ioapic_scope_size);
     drhd->type = cpu_to_le16(ACPI_DMAR_TYPE_HARDWARE_UNIT);
-    drhd->length = cpu_to_le16(sizeof(*drhd) + ioapic_scope_size);
-    drhd->flags = ACPI_DMAR_INCLUDE_PCI_ALL;
+    drhd->length =
+        cpu_to_le16(sizeof(*drhd) + ioapic_scope_size + scope_blob->len);
+    drhd->flags = 0;            /* Don't include all pci device */
     drhd->pci_segment = cpu_to_le16(0);
     drhd->address = cpu_to_le64(Q35_HOST_BRIDGE_IOMMU_ADDR);
 
@@ -2052,6 +2112,10 @@ build_dmar_q35(GArray *table_data, BIOSLinker *linker, 
const char *oem_id,
     scope->path[0].device = PCI_SLOT(Q35_PSEUDO_DEVFN_IOAPIC);
     scope->path[0].function = PCI_FUNC(Q35_PSEUDO_DEVFN_IOAPIC);
 
+    /* Add scope found above */
+    g_array_append_vals(table_data, scope_blob->data, scope_blob->len);
+    g_array_free(scope_blob, true);
+
     if (iommu->dt_supported) {
         atsr = acpi_data_push(table_data, sizeof(*atsr));
         atsr->type = cpu_to_le16(ACPI_DMAR_TYPE_ATSR);
-- 
2.19.1