From 2d211fe6f9d511cdcce344f1c9c422fe33b5a957 Mon Sep 17 00:00:00 2001 From: Evgeny Voevodin Date: Thu, 7 May 2026 18:08:07 +0000 Subject: [PATCH] lib: sbi: hart: Detect and enable Smrnmi before trap-based feature detection The location of the RNMI/E trap vectors in the Smrnmi extension is implementation-defined, so platforms with vendor-specific NMI vector mechanisms must install the firmware's NMI entry points themselves. Add an smrnmi_handlers_init() callback to sbi_platform_operations that receives the firmware entry points and lets platform code install them at the hardware-specific vector locations. Two pointers are passed: - _trap_rnmi_handler: the dedicated RNMI entry point that saves context using the Smrnmi MN* CSRs and returns via mnret. - _trap_handler: the regular M-mode trap entry since RNME is taken as a regular M-mode trap with NMIE=0. When Smrnmi is present, install the platform's NMI vectors via the new callback, initialize MNSCRATCH with the per-hart scratch pointer, and set MNSTATUS.NMIE. Smrnmi-enabled platforms must register smrnmi_handlers_init; if the extension is detected but no callback is registered, sbi_panic() is called since enabling NMIs without handlers in place would route subsequent traps into nowhere. Signed-off-by: Evgeny Voevodin Reviewed-by: Anup Patel Link: https://lore.kernel.org/r/88b1470e1e3348d454b4b995a11a85c01914f7af.1778176768.git.evvoevod@tenstorrent.com Signed-off-by: Anup Patel --- include/sbi/sbi_platform.h | 4 ++++ lib/sbi/sbi_hart.c | 20 ++++++++++++++++++++ 2 files changed, 24 insertions(+) diff --git a/include/sbi/sbi_platform.h b/include/sbi/sbi_platform.h index 715df499..fe382b56 100644 --- a/include/sbi/sbi_platform.h +++ b/include/sbi/sbi_platform.h @@ -150,6 +150,10 @@ struct sbi_platform_operations { /** platform specific pmp disable on current HART */ void (*pmp_disable)(unsigned int n); + /** platform specific Smrnmi handlers init on current HART */ + void (*smrnmi_handlers_init)(void (*rnmi_handler)(void), + void (*rnme_handler)(void)); + /** platform specific Smrnmi NMI handler. * Returns SBI_SUCCESS on success, error code if NMI cannot be handled. */ int (*rnmi_handler)(struct sbi_trap_context *tcntx); diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c index 781161e5..92c602aa 100644 --- a/lib/sbi/sbi_hart.c +++ b/lib/sbi/sbi_hart.c @@ -532,6 +532,26 @@ static int hart_detect_features(struct sbi_scratch *scratch) if (rc) return rc; + if (sbi_hart_has_extension(scratch, SBI_HART_EXT_SMRNMI)) { + const struct sbi_platform *plat = sbi_platform_thishart_ptr(); + const struct sbi_platform_operations *ops = sbi_platform_ops(plat); + extern void _trap_rnmi_handler(void); + extern void _trap_handler(void); + + if (!ops || !ops->smrnmi_handlers_init) + sbi_panic("Smrnmi detected, but platform lacks smrnmi_handlers_init callback\n"); + + /* Reuse _trap_handler for the RNME slot since RNME is taken + * as a regular M-mode trap with NMIE=0. */ + ops->smrnmi_handlers_init(_trap_rnmi_handler, _trap_handler); + + /* Initialize MNSCRATCH for the RNMI handler */ + csr_write(CSR_MNSCRATCH, scratch); + + /* Enable NMIs */ + csr_set(CSR_MNSTATUS, MNSTATUS_NMIE); + } + #define __check_hpm_csr(__csr, __mask) \ oldval = csr_read_allowed(__csr, &trap); \ if (!trap.cause) { \