[PATCH v3 2/7] riscv: smp: fail booting up smp if inconsistent vlen is detected

From: Andy Chiu <andy.chiu@sifive.com>
To: Paul Walmsley <paul.walmsley@sifive.com>,
	 Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	 Andy Chiu <andy.chiu@sifive.com>,
	Vincent Chen <vincent.chen@sifive.com>,
	 Heiko Stuebner <heiko@sntech.de>,
	Conor Dooley <conor.dooley@microchip.com>,
	 Conor Dooley <conor@kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	 Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	 Jonathan Corbet <corbet@lwn.net>
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	 Palmer Dabbelt <palmer@rivosinc.com>,
	 Greentime Hu <greentime.hu@sifive.com>,
	Guo Ren <guoren@kernel.org>,
	 devicetree@vger.kernel.org, linux-doc@vger.kernel.org
Subject: [PATCH v3 2/7] riscv: smp: fail booting up smp if inconsistent vlen is detected
Date: Mon, 18 Mar 2024 18:39:55 +0800	[thread overview]
Message-ID: <20240318-zve-detection-v3-2-e12d42107fa8@sifive.com> (raw)
In-Reply-To: <20240318-zve-detection-v3-0-e12d42107fa8@sifive.com>

Currently we only support Vector for SMP platforms, that is, all SMP
cores have the same vlenb. If we happen to detect a mismatching vlen, it
is better to just fail bootting it up to prevent further race/scheduling
issues.

Also, move .Lsecondary_park forward and chage `tail smp_callin` into a
regular call in the early assembly. So a core would be parked right
after a return from smp_callin. Note that a successful smp_callin
does not return.

Fixes: 7017858eb2d7 ("riscv: Introduce riscv_v_vsize to record size of Vector context")
Reported-by: Conor Dooley <conor.dooley@microchip.com>
Closes: https://lore.kernel.org/linux-riscv/20240228-vicinity-cornstalk-4b8eb5fe5730@spud/
Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
---
Changelog v2:
 - update commit message to explain asm code change (Conor)
---
 arch/riscv/kernel/head.S    | 14 +++++++-------
 arch/riscv/kernel/smpboot.c | 14 +++++++++-----
 2 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 4236a69c35cb..a158fa9f2656 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -165,9 +165,15 @@ secondary_start_sbi:
 #endif
 	call .Lsetup_trap_vector
 	scs_load_current
-	tail smp_callin
+	call smp_callin
 #endif /* CONFIG_SMP */
 
+.align 2
+.Lsecondary_park:
+	/* We lack SMP support or have too many harts, so park this hart */
+	wfi
+	j .Lsecondary_park
+
 .align 2
 .Lsetup_trap_vector:
 	/* Set trap vector to exception handler */
@@ -181,12 +187,6 @@ secondary_start_sbi:
 	csrw CSR_SCRATCH, zero
 	ret
 
-.align 2
-.Lsecondary_park:
-	/* We lack SMP support or have too many harts, so park this hart */
-	wfi
-	j .Lsecondary_park
-
 SYM_CODE_END(_start)
 
 SYM_CODE_START(_start_kernel)
diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index cfbe4b840d42..1f86ee10192f 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -218,6 +218,15 @@ asmlinkage __visible void smp_callin(void)
 	struct mm_struct *mm = &init_mm;
 	unsigned int curr_cpuid = smp_processor_id();
 
+	if (has_vector()) {
+		/*
+		 * Return as early as possible so the hart with a mismatching
+		 * vlen won't boot.
+		 */
+		if (riscv_v_setup_vsize())
+			return;
+	}
+
 	/* All kernel threads share the same mm context.  */
 	mmgrab(mm);
 	current->active_mm = mm;
@@ -230,11 +239,6 @@ asmlinkage __visible void smp_callin(void)
 	numa_add_cpu(curr_cpuid);
 	set_cpu_online(curr_cpuid, 1);
 
-	if (has_vector()) {
-		if (riscv_v_setup_vsize())
-			elf_hwcap &= ~COMPAT_HWCAP_ISA_V;
-	}
-
 	riscv_user_isa_enable();
 
 	/*

-- 
2.44.0.rc2

