Implement construct_domain() function for RISC-V, which performs initial setup
for the domain's first vCPU, loads the kernel, initrd, and device tree,
and sets up guest CPU registers for boot.

It also creates additional vCPUs up to max_vcpus and assigns the device tree
address and boot cpuid in registers.

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
---
 xen/arch/riscv/domain-build.c | 46 +++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 xen/arch/riscv/domain-build.c

diff --git a/xen/arch/riscv/domain-build.c b/xen/arch/riscv/domain-build.c
new file mode 100644
index 000000000000..0ce903a911ae
--- /dev/null
+++ b/xen/arch/riscv/domain-build.c
@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include <xen/fdt-domain-build.h>
+#include <xen/fdt-kernel.h>
+#include <xen/init.h>
+#include <xen/sched.h>
+
+#include <asm/current.h>
+#include <asm/guest_access.h>
+
+int __init construct_domain(struct domain *d, struct kernel_info *kinfo)
+{
+    struct vcpu *v = d->vcpu[0];
+    struct cpu_user_regs *regs = vcpu_guest_cpu_user_regs(v);
+
+    BUG_ON(d->vcpu[0] == NULL);
+    BUG_ON(v->is_initialised);
+
+    kernel_load(kinfo);
+    initrd_load(kinfo, copy_to_guest_phys);
+    dtb_load(kinfo, copy_to_guest_phys);
+
+    regs->sepc = kinfo->entry;
+
+    /* Guest boot cpuid = 0 */
+    regs->a0 = 0;
+    regs->a1 = kinfo->dtb_paddr;
+
+    for ( unsigned int i = 1; i < d->max_vcpus; i++ )
+    {
+        if ( vcpu_create(d, i) == NULL )
+        {
+            printk("Failed to allocate %pd v%d\n", d, i);
+            break;
+        }
+
+        printk("Created vcpu %d for %pd\n", i, d);
+    }
+
+    domain_update_node_affinity(d);
+
+    v->is_initialised = 1;
+    clear_bit(_VPF_down, &v->pause_flags);
+
+    return 0;
+}
-- 
2.53.0

On 10.03.2026 18:08, Oleksii Kurochko wrote:
> --- /dev/null
> +++ b/xen/arch/riscv/domain-build.c
> @@ -0,0 +1,46 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +
> +#include <xen/fdt-domain-build.h>
> +#include <xen/fdt-kernel.h>
> +#include <xen/init.h>
> +#include <xen/sched.h>
> +
> +#include <asm/current.h>
> +#include <asm/guest_access.h>
> +
> +int __init construct_domain(struct domain *d, struct kernel_info *kinfo)

Are you actually altering what kinfo points to?

> +{
> +    struct vcpu *v = d->vcpu[0];
> +    struct cpu_user_regs *regs = vcpu_guest_cpu_user_regs(v);
> +
> +    BUG_ON(d->vcpu[0] == NULL);

Why not simply "!v"?

Also, while in the cover letter you state a dependency on another series,
this is somewhat unwieldy here. From the titles there I can't deduce which
of the patches would introduce vcpu_guest_cpu_user_regs(). Yet I would
have wanted to double check that it doesn't de-reference v already.

> +    BUG_ON(v->is_initialised);
> +
> +    kernel_load(kinfo);
> +    initrd_load(kinfo, copy_to_guest_phys);
> +    dtb_load(kinfo, copy_to_guest_phys);

These all return void, despite this also being used for non-Dom0. Is it
really fatal to a dom0less system if one out of many domains fail to be
built? Especially when, despite the name, there is a Dom0?

> +    regs->sepc = kinfo->entry;
> +
> +    /* Guest boot cpuid = 0 */
> +    regs->a0 = 0;
> +    regs->a1 = kinfo->dtb_paddr;
> +
> +    for ( unsigned int i = 1; i < d->max_vcpus; i++ )
> +    {
> +        if ( vcpu_create(d, i) == NULL )
> +        {
> +            printk("Failed to allocate %pd v%d\n", d, i);
> +            break;

And no error is indicated to the caller?

> +        }
> +
> +        printk("Created vcpu %d for %pd\n", i, d);

dprintk() at most, and if so, then please use %pv.

> +    }
> +
> +    domain_update_node_affinity(d);
> +
> +    v->is_initialised = 1;

This is a boolean field, so the rhs wants to be "true".

Jan