[PATCH 2/3] lib: sbi: Enable Smrnmi extension handler
Nylon Chen
nylon.chen at sifive.com
Thu Jan 29 00:13:42 PST 2026
Enable the Smrnmi extension by:
1. Adding sbi_rnmi_vector_init() to allocate per-HART RNMI context and enable RNMI via MNSTATUS.NMIE
2. Saving and restoring CSR_MNSCRATCH and CSR_MNSTATUS across non-retentive suspend/resume
3. Calling sbi_rnmi_vector_init() from the cold and warm init paths
Co-developed-by: Zong Li <zong.li at sifive.com>
Signed-off-by: Zong Li <zong.li at sifive.com>
Suggested-by: Nick Hu <nick.hu at sifive.com>
Suggested-by: Samuel Holland <samuel.holland at sifive.com>
Signed-off-by: Nylon Chen <nylon.chen at sifive.com>
Signed-off-by: Yong-Xuan Wang <yongxuan.wang at sifive.com>
---
include/sbi/sbi_hart.h | 1 +
include/sbi/sbi_platform.h | 9 +++++++++
lib/sbi/sbi_hart.c | 43 +++++++++++++++++++++++++++++++++++++++++++
lib/sbi/sbi_hsm.c | 10 ++++++++++
lib/sbi/sbi_init.c | 8 ++++++++
5 files changed, 71 insertions(+)
diff --git a/include/sbi/sbi_hart.h b/include/sbi/sbi_hart.h
index 7d038a18..3e442546 100644
--- a/include/sbi/sbi_hart.h
+++ b/include/sbi/sbi_hart.h
@@ -128,6 +128,7 @@ struct sbi_scratch;
int sbi_hart_reinit(struct sbi_scratch *scratch);
int sbi_hart_init(struct sbi_scratch *scratch, bool cold_boot);
+int sbi_rnmi_vector_init(struct sbi_scratch *scratch, bool cold_boot);
extern void (*sbi_hart_expected_trap)(void);
diff --git a/include/sbi/sbi_platform.h b/include/sbi/sbi_platform.h
index e65d9877..c4f6c456 100644
--- a/include/sbi/sbi_platform.h
+++ b/include/sbi/sbi_platform.h
@@ -149,6 +149,15 @@ struct sbi_platform_operations {
unsigned long log2len);
/** platform specific pmp disable on current HART */
void (*pmp_disable)(unsigned int n);
+ /**
+ * Platform-specific helper to program the RNMI trap vector.
+ *
+ * The core will call this from sbi_rnmi_vector_init() with the
+ * firmware RNMI handler entry address (rnmi_handler) and the
+ * cold_boot flag. Platforms that support Smrnmi should implement
+ * this; others can leave it NULL.
+ */
+ int (*set_rnmi_trap_vector)(uintptr_t handler_addr, bool cold_boot);
};
/** Platform default per-HART stack size for exception/interrupt handling */
diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
index 495ad1d8..baebc438 100644
--- a/lib/sbi/sbi_hart.c
+++ b/lib/sbi/sbi_hart.c
@@ -28,6 +28,7 @@ extern void __sbi_expected_trap_hext(void);
void (*sbi_hart_expected_trap)(void) = &__sbi_expected_trap;
unsigned long hart_features_offset;
+static unsigned long rnmi_context_offset;
static void mstatus_init(struct sbi_scratch *scratch)
{
@@ -833,3 +834,45 @@ sbi_hart_switch_mode(unsigned long arg0, unsigned long arg1,
__asm__ __volatile__("mret" : : "r"(a0), "r"(a1));
__builtin_unreachable();
}
+
+int sbi_rnmi_vector_init(struct sbi_scratch *scratch, bool cold_boot)
+{
+ unsigned long rnmi_sp;
+ void *rnmi_ctx;
+ const struct sbi_platform *plat = sbi_platform_ptr(scratch);
+ const struct sbi_platform_operations *ops =
+ plat ? sbi_platform_ops(plat) : NULL;
+
+ /* If the hart does not support Smrnmi then nothing to do. */
+ if (!sbi_hart_has_extension(scratch, SBI_HART_EXT_SMRNMI))
+ return 0;
+
+ /* Platform without RNMI vector hook cannot support RNMI. */
+ if (!ops || !ops->set_rnmi_trap_vector)
+ return 0;
+
+ /*
+ * Allocate per-HART RNMI context area once during cold boot and
+ * remember its offset inside struct sbi_scratch. All harts use
+ * the same offset but different scratch pointers, so each hart
+ * gets its own RNMI context.
+ */
+ if (cold_boot) {
+ rnmi_context_offset = sbi_scratch_alloc_offset(SBI_TRAP_REGS_SIZE);
+ if (!rnmi_context_offset)
+ return SBI_ENOMEM;
+ }
+
+ if (!rnmi_context_offset)
+ return 0;
+
+ /* Set CSR_MNSCRATCH to point above the RNMI trap-regs save area. */
+ rnmi_ctx = sbi_scratch_offset_ptr(scratch, rnmi_context_offset);
+ rnmi_sp = (unsigned long)rnmi_ctx + SBI_TRAP_REGS_SIZE;
+ csr_write(CSR_MNSCRATCH, rnmi_sp);
+
+ /* Enable RNMI now that CSR_MNSCRATCH and the trap vector are set up. */
+ csr_set(CSR_MNSTATUS, MNSTATUS_NMIE);
+
+ return 0;
+}
diff --git a/lib/sbi/sbi_hsm.c b/lib/sbi/sbi_hsm.c
index 0a355f9c..f259c257 100644
--- a/lib/sbi/sbi_hsm.c
+++ b/lib/sbi/sbi_hsm.c
@@ -49,6 +49,8 @@ struct sbi_hsm_data {
unsigned long saved_medeleg;
unsigned long saved_mideleg;
u64 saved_menvcfg;
+ unsigned long saved_mnscratch;
+ unsigned long saved_mnstatus;
atomic_t start_ticket;
};
@@ -430,6 +432,10 @@ void __sbi_hsm_suspend_non_ret_save(struct sbi_scratch *scratch)
hdata->saved_mideleg = csr_read(CSR_MIDELEG);
if (sbi_hart_priv_version(scratch) >= SBI_HART_PRIV_VER_1_12)
hdata->saved_menvcfg = csr_read64(CSR_MENVCFG);
+ if (sbi_hart_has_extension(scratch, SBI_HART_EXT_SMRNMI)) {
+ hdata->saved_mnscratch = csr_read(CSR_MNSCRATCH);
+ hdata->saved_mnstatus = csr_read(CSR_MNSTATUS);
+ }
}
static void __sbi_hsm_suspend_non_ret_restore(struct sbi_scratch *scratch)
@@ -437,6 +443,10 @@ static void __sbi_hsm_suspend_non_ret_restore(struct sbi_scratch *scratch)
struct sbi_hsm_data *hdata = sbi_scratch_offset_ptr(scratch,
hart_data_offset);
+ if (sbi_hart_has_extension(scratch, SBI_HART_EXT_SMRNMI)) {
+ csr_write(CSR_MNSCRATCH, hdata->saved_mnscratch);
+ csr_write(CSR_MNSTATUS, hdata->saved_mnstatus);
+ }
if (sbi_hart_priv_version(scratch) >= SBI_HART_PRIV_VER_1_12)
csr_write64(CSR_MENVCFG, hdata->saved_menvcfg);
csr_write(CSR_MIDELEG, hdata->saved_mideleg);
diff --git a/lib/sbi/sbi_init.c b/lib/sbi/sbi_init.c
index 5259064b..60a24809 100644
--- a/lib/sbi/sbi_init.c
+++ b/lib/sbi/sbi_init.c
@@ -273,6 +273,10 @@ static void __noreturn init_coldboot(struct sbi_scratch *scratch, u32 hartid)
if (rc)
sbi_hart_hang();
+ rc = sbi_rnmi_vector_init(scratch, true);
+ if (rc)
+ sbi_hart_hang();
+
rc = sbi_pmu_init(scratch, true);
if (rc) {
sbi_printf("%s: pmu init failed (error %d)\n",
@@ -432,6 +436,10 @@ static void __noreturn init_warm_startup(struct sbi_scratch *scratch,
if (rc)
sbi_hart_hang();
+ rc = sbi_rnmi_vector_init(scratch, false);
+ if (rc)
+ sbi_hart_hang();
+
rc = sbi_pmu_init(scratch, false);
if (rc)
sbi_hart_hang();
--
2.43.7
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