linux-kernel - [RFC PATCH v2 03/11] RISC-V: Setup exception vector early

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Message-Id: <20200706172609.25965-4-atish.patra@wdc.com>
Date:   Mon,  6 Jul 2020 10:26:01 -0700
From:   Atish Patra <atish.patra@....com>
To:     linux-kernel@...r.kernel.org
Cc:     Atish Patra <atish.patra@....com>,
        Ard Biesheuvel <ardb@...nel.org>, linux-efi@...r.kernel.org,
        linux-riscv@...ts.infradead.org,
        Masahiro Yamada <masahiroy@...nel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Heinrich Schuchardt <xypron.glpk@....de>
Subject: [RFC PATCH v2 03/11] RISC-V: Setup exception vector early

The trap vector is set only in trap_init which may be too late in some
cases. Early ioremap/efi spits many warning messages which may be useful.

Setup the trap vector early so that any warning/bug can be handled before
generic code invokes trap_init.

Signed-off-by: Atish Patra <atish.patra@....com>
---
 arch/riscv/kernel/head.S    | 10 ++++++++--
 arch/riscv/kernel/smpboot.c |  1 -
 arch/riscv/kernel/traps.c   |  8 +-------
 3 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index c5b529234ad8..eb123eda3663 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -77,10 +77,16 @@ relocate:
 	csrw CSR_SATP, a0
 .align 2
 1:
-	/* Set trap vector to spin forever to help debug */
-	la a0, .Lsecondary_park
+	/* Set trap vector to exception handler */
+	la a0, handle_exception
 	csrw CSR_TVEC, a0
 
+	/*
+	 * Set sup0 scratch register to 0, indicating to exception vector that
+	 * we are presently executing in kernel.
+	 */
+	csrw CSR_SCRATCH, zero
+
 	/* Reload the global pointer */
 .option push
 .option norelax
diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index 4e9922790f6e..5a9c127a380e 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -154,7 +154,6 @@ asmlinkage __visible void smp_callin(void)
 	mmgrab(mm);
 	current->active_mm = mm;
 
-	trap_init();
 	notify_cpu_starting(smp_processor_id());
 	update_siblings_masks(smp_processor_id());
 	set_cpu_online(smp_processor_id(), 1);
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 7d95cce5e47c..ad14f4466d92 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -174,13 +174,7 @@ int is_valid_bugaddr(unsigned long pc)
 }
 #endif /* CONFIG_GENERIC_BUG */
 
+/* stvec & scratch is already set from head.S */
 void trap_init(void)
 {
-	/*
-	 * Set sup0 scratch register to 0, indicating to exception vector
-	 * that we are presently executing in the kernel
-	 */
-	csr_write(CSR_SCRATCH, 0);
-	/* Set the exception vector address */
-	csr_write(CSR_TVEC, &handle_exception);
 }
-- 
2.24.0