[RFC PATCH 3/3] sifive_dev_platform: Set default MMIO region when SmePMP is enabled

[Yu-Chien Peter Lin]

Set a default MMIO region with a single SmePMP entry, which allows us
to save entries for M-mode only devices. The default entry has M-/S-mode
shared permission, so system-level resource protection, such as RISC-V
World extension and WorldGuard checker, will be introduced to protect
M-mode only region access from lower privilege modes.

Reviewed-by: Greentime Hu <greentime.hu at sifive.com>
Reviewed-by: Zong Li <zong.li at sifive.com>
Signed-off-by: Yu-Chien Peter Lin <peter.lin at sifive.com>
---
 platform/generic/sifive/sifive_dev_platform.c | 48 +++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/platform/generic/sifive/sifive_dev_platform.c b/platform/generic/sifive/sifive_dev_platform.c
index facc044f1..9799e5b88 100644
--- a/platform/generic/sifive/sifive_dev_platform.c
+++ b/platform/generic/sifive/sifive_dev_platform.c
@@ -5,10 +5,58 @@
  */
 
 #include <platform_override.h>
+#include <sbi/sbi_hart.h>
+#include <sbi/sbi_scratch.h>
+
+/*
+ * Instead of allocating individual PMP entries for each M-mode
+ * MMIO driver, configure SMEPMP regions to grant R/W permission
+ * to peripheral and system ports for all privilege modes.
+ * Finer-grained access control is enforced by wgChecker rules.
+ */
+static int sifive_smepmp_setup(void)
+{
+	struct sbi_scratch *scratch = sbi_scratch_thishart_ptr();
+	int rc;
+
+	if (!sbi_hart_has_extension(scratch, SBI_HART_EXT_SMEPMP))
+		return 0;
+
+	/* Peripheral port region: 0 to 2GiB */
+	rc = sbi_domain_root_add_memrange(0x0, 0x80000000, 0x80000000,
+					  SBI_DOMAIN_MEMREGION_MMIO |
+					  SBI_DOMAIN_MEMREGION_SHARED_SURW_MRW);
+	if (rc)
+		return rc;
+
+	/* System port region: 512GiB to 1TiB */
+	rc = sbi_domain_root_add_memrange(0x8000000000, 0x8000000000, 0x8000000000,
+					  SBI_DOMAIN_MEMREGION_MMIO |
+					  SBI_DOMAIN_MEMREGION_SHARED_SURW_MRW);
+	if (rc)
+		return rc;
+
+	return 0;
+}
+
+static int sifive_early_init(bool cold_boot)
+{
+	int rc;
+
+	if (cold_boot) {
+		rc = sifive_smepmp_setup();
+		if (rc)
+			return rc;
+	}
+
+	return generic_early_init(cold_boot);
+}
 
 static int sifive_platform_init(const void *fdt, int nodeoff,
 				const struct fdt_match *match)
 {
+	generic_platform_ops.early_init = sifive_early_init;
+
 	return 0;
 }
 
-- 
2.43.7