[PATCH RFCv1 03/10] hw/arm/virt: Get the number of host-level SMMUv3 instances

[Nicolin Chen]

Nested SMMUv3 feature requires the support/presence of host-level SMMUv3
instance(s). Add a helper to read the sysfs for the number of instances.
Log them in a vms list using a new struct VirtNestedSmmu.

This will be used by a following patch to assign a passthrough device to
corresponding nested SMMUv3 instance.

Signed-off-by: Nicolin Chen <nicol...@nvidia.com>
---
 hw/arm/virt.c         | 35 +++++++++++++++++++++++++++++++++++
 include/hw/arm/virt.h |  8 ++++++++
 2 files changed, 43 insertions(+)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 71093d7c60..be3d8b0ce6 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -2668,6 +2668,37 @@ static char *virt_get_iommu(Object *obj, Error **errp)
     }
 }
 
+static int virt_get_num_nested_smmus(VirtMachineState *vms, Error **errp)
+{
+    VirtNestedSmmu *nested_smmu;
+    struct dirent *dent;
+    DIR *dir = NULL;
+    int num = 0;
+
+    dir = opendir("/sys/class/iommu");
+    if (!dir) {
+        error_setg_errno(errp, errno, "couldn't open /sys/class/iommu");
+        return 0;
+    }
+
+    while ((dent = readdir(dir))) {
+        if (!strncmp(dent->d_name, "smmu3.0x", 7)) {
+            nested_smmu = g_new0(VirtNestedSmmu, 1);
+            nested_smmu->index = num;
+            nested_smmu->smmu_node = g_strdup(dent->d_name);
+            QLIST_INSERT_HEAD(&vms->nested_smmu_list, nested_smmu, next);
+            num++;
+        }
+    }
+
+    if (num == 0) {
+        error_setg_errno(errp, errno,
+                         "couldn't find any SMMUv3 HW to setup nesting");
+    }
+
+    return num;
+}
+
 static void virt_set_iommu(Object *obj, const char *value, Error **errp)
 {
     VirtMachineState *vms = VIRT_MACHINE(obj);
@@ -2676,6 +2707,7 @@ static void virt_set_iommu(Object *obj, const char 
*value, Error **errp)
         vms->iommu = VIRT_IOMMU_SMMUV3;
     } else if (!strcmp(value, "nested-smmuv3")) {
         vms->iommu = VIRT_IOMMU_NESTED_SMMUV3;
+        vms->num_nested_smmus = virt_get_num_nested_smmus(vms, errp);
     } else if (!strcmp(value, "none")) {
         vms->iommu = VIRT_IOMMU_NONE;
     } else {
@@ -3232,6 +3264,9 @@ static void virt_instance_init(Object *obj)
     /* The default root bus is attached to iommu by default */
     vms->default_bus_bypass_iommu = false;
 
+    /* Default disallows nested SMMU instantiation */
+    vms->num_nested_smmus = 0;
+
     /* Default disallows RAS instantiation */
     vms->ras = false;
 
diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
index d5cbce1a30..e0c07527c4 100644
--- a/include/hw/arm/virt.h
+++ b/include/hw/arm/virt.h
@@ -135,6 +135,12 @@ struct VirtMachineClass {
     bool no_ns_el2_virt_timer_irq;
 };
 
+typedef struct VirtNestedSmmu {
+    int index;
+    char *smmu_node;
+    QLIST_ENTRY(VirtNestedSmmu) next;
+} VirtNestedSmmu;
+
 struct VirtMachineState {
     MachineState parent;
     Notifier machine_done;
@@ -153,6 +159,7 @@ struct VirtMachineState {
     bool ras;
     bool mte;
     bool dtb_randomness;
+    int num_nested_smmus;
     OnOffAuto acpi;
     VirtGICType gic_version;
     IOMMUFDBackend *iommufd;
@@ -178,6 +185,7 @@ struct VirtMachineState {
     char *oem_id;
     char *oem_table_id;
     bool ns_el2_virt_timer_irq;
+    QLIST_HEAD(, VirtNestedSmmu) nested_smmu_list;
 };
 
 #define VIRT_ECAM_ID(high) (high ? VIRT_HIGH_PCIE_ECAM : VIRT_PCIE_ECAM)
-- 
2.43.0