[PATCH v1 3/3] xen/riscv: add RISC-V virtual SBI base extension support for guests

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

Add support of virtual SBI base extension calls for RISC-V guests, delegating
hardware-specific queries to the underlying SBI and handling version and
firmware ID queries directly.

The changes include:
1. Define new SBI base extension function IDs (SBI_EXT_BASE_GET_MVENDORID,
   SBI_EXT_BASE_GET_MARCHID, SBI_EXT_BASE_GET_MIMPID).
2. Make sbi_spec_version, sbi_fw_id, and sbi_fw_version global variables for
   use in virtual SBI handling, removing redundant local declarations in
   sbi_init.
3. Implement handling of SBI base extension functions, including version,
   firmware ID, and machine-specific queries.

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
 xen/arch/riscv/include/asm/sbi.h          |  3 ++
 xen/arch/riscv/sbi.c                      |  8 ++--
 xen/arch/riscv/vsbi/Makefile              |  1 +
 xen/arch/riscv/vsbi/vsbi-base-extension.c | 52 +++++++++++++++++++++++
 4 files changed, 61 insertions(+), 3 deletions(-)
 create mode 100644 xen/arch/riscv/vsbi/vsbi-base-extension.c

diff --git a/xen/arch/riscv/include/asm/sbi.h b/xen/arch/riscv/include/asm/sbi.h
index e7d5d707b1..98ba872ef3 100644
--- a/xen/arch/riscv/include/asm/sbi.h
+++ b/xen/arch/riscv/include/asm/sbi.h
@@ -32,6 +32,9 @@
 #define SBI_EXT_BASE_GET_IMP_ID         0x1
 #define SBI_EXT_BASE_GET_IMP_VERSION    0x2
 #define SBI_EXT_BASE_PROBE_EXT          0x3
+#define SBI_EXT_BASE_GET_MVENDORID      0x4
+#define SBI_EXT_BASE_GET_MARCHID        0x5
+#define SBI_EXT_BASE_GET_MIMPID         0x6
 
 /* SBI function IDs for RFENCE extension */
 #define SBI_EXT_RFENCE_REMOTE_FENCE_I           0x0
diff --git a/xen/arch/riscv/sbi.c b/xen/arch/riscv/sbi.c
index 425dce44c6..97cbf84c21 100644
--- a/xen/arch/riscv/sbi.c
+++ b/xen/arch/riscv/sbi.c
@@ -23,7 +23,9 @@
 #include <asm/processor.h>
 #include <asm/sbi.h>
 
-static unsigned long __ro_after_init sbi_spec_version = 
SBI_SPEC_VERSION_DEFAULT;
+unsigned long __ro_after_init sbi_spec_version = SBI_SPEC_VERSION_DEFAULT;
+long __ro_after_init sbi_fw_id;
+long __ro_after_init sbi_fw_version;
 
 struct sbiret sbi_ecall(unsigned long ext, unsigned long fid,
                         unsigned long arg0, unsigned long arg1,
@@ -313,8 +315,8 @@ int __init sbi_init(void)
 
     if ( !sbi_spec_is_0_1() )
     {
-        long sbi_fw_id = sbi_get_firmware_id();
-        long sbi_fw_version = sbi_get_firmware_version();
+        sbi_fw_id = sbi_get_firmware_id();
+        sbi_fw_version = sbi_get_firmware_version();
 
         BUG_ON((sbi_fw_id < 0) || (sbi_fw_version < 0));
 
diff --git a/xen/arch/riscv/vsbi/Makefile b/xen/arch/riscv/vsbi/Makefile
index 4da625db9a..07ae27b99e 100644
--- a/xen/arch/riscv/vsbi/Makefile
+++ b/xen/arch/riscv/vsbi/Makefile
@@ -1,2 +1,3 @@
 obj-y += vsbi.o
+obj-y += vsbi-base-extension.o
 obj-y += vsbi-legacy-extension.o
diff --git a/xen/arch/riscv/vsbi/vsbi-base-extension.c 
b/xen/arch/riscv/vsbi/vsbi-base-extension.c
new file mode 100644
index 0000000000..88f4567cb1
--- /dev/null
+++ b/xen/arch/riscv/vsbi/vsbi-base-extension.c
@@ -0,0 +1,52 @@
+
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <xen/lib.h>
+#include <xen/sched.h>
+
+#include <asm/processor.h>
+#include <asm/sbi.h>
+#include <asm/vsbi.h>
+
+extern unsigned long __ro_after_init sbi_spec_version;
+extern long __ro_after_init sbi_fw_id;
+extern long __ro_after_init sbi_fw_version;
+
+static int vsbi_base_ecall_handler(struct vcpu *vcpu, unsigned long eid,
+                                   unsigned long fid,
+                                   struct cpu_user_regs *regs)
+{
+    int ret = 0;
+    struct sbiret sbi_ret;
+
+    switch ( fid ) {
+    case SBI_EXT_BASE_GET_SPEC_VERSION:
+        regs->a1 = sbi_spec_version;
+        break;
+    case SBI_EXT_BASE_GET_IMP_ID:
+        regs->a1 = sbi_fw_id;
+        break;
+    case SBI_EXT_BASE_GET_IMP_VERSION:
+        regs->a1 = sbi_fw_version;
+        break;
+    case SBI_EXT_BASE_GET_MVENDORID:
+    case SBI_EXT_BASE_GET_MARCHID:
+    case SBI_EXT_BASE_GET_MIMPID:
+        sbi_ret = sbi_ecall(SBI_EXT_BASE, fid, 0, 0, 0, 0, 0, 0);
+        ret = sbi_ret.error;
+        regs->a1 = sbi_ret.value;
+        break;
+    case SBI_EXT_BASE_PROBE_EXT:
+        regs->a1 = vsbi_find_extension(regs->a0) ? 1 : 0;
+        break;
+    default:
+        panic("%s: Unsupported ecall: FID: #%lx, EID: #%lx\n",
+              __func__, fid, eid);
+        break;
+    }
+
+    return ret;
+}
+
+VSBI_EXT_START(base, SBI_EXT_BASE, SBI_EXT_BASE, vsbi_base_ecall_handler)
+VSBI_EXT_END
-- 
2.52.0