From: Will Deacon <will@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: mark.rutland@arm.com, catalin.marinas@arm.com,
Will Deacon <will@kernel.org>
Subject: [PATCH 2/3] arm64: smp: Don't enter kernel with NULL stack pointer or task struct
Date: Tue, 27 Aug 2019 16:18:14 +0100 [thread overview]
Message-ID: <20190827151815.2160-3-will@kernel.org> (raw)
In-Reply-To: <20190827151815.2160-1-will@kernel.org>
Although SMP bringup is inherently racy, we can significantly reduce
the window during which secondary CPUs can unexpectedly enter the
kernel by sanity checking the 'stack' and 'task' fields of the
'secondary_data' structure. If the booting CPU gave up waiting for us,
then they will have been cleared to NULL and we should spin in a WFE; WFI
loop instead.
Signed-off-by: Will Deacon <will@kernel.org>
---
arch/arm64/kernel/head.S | 8 ++++++++
arch/arm64/kernel/smp.c | 1 +
2 files changed, 9 insertions(+)
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 2cdacd1c141b..0baadf335172 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -724,14 +724,22 @@ __secondary_switched:
adr_l x0, secondary_data
ldr x1, [x0, #CPU_BOOT_STACK] // get secondary_data.stack
+ cbz x1, __secondary_too_slow
mov sp, x1
ldr x2, [x0, #CPU_BOOT_TASK]
+ cbz x2, __secondary_too_slow
msr sp_el0, x2
mov x29, #0
mov x30, #0
b secondary_start_kernel
ENDPROC(__secondary_switched)
+__secondary_too_slow:
+ wfe
+ wfi
+ b __secondary_too_slow
+ENDPROC(__secondary_too_slow)
+
/*
* The booting CPU updates the failed status @__early_cpu_boot_status,
* with MMU turned off.
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 63c7a7682e93..1f8aeb77cba5 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -136,6 +136,7 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
secondary_data.task = NULL;
secondary_data.stack = NULL;
+ __flush_dcache_area(&secondary_data, sizeof(secondary_data));
status = READ_ONCE(secondary_data.status);
if (ret && status) {
--
2.11.0
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next prev parent reply other threads:[~2019-08-27 15:18 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-27 15:18 [PATCH 0/3] Try to make SMP booting slightly less fragile Will Deacon
2019-08-27 15:18 ` [PATCH 1/3] arm64: smp: Increase secondary CPU boot timeout value Will Deacon
2019-08-27 16:05 ` Mark Rutland
2019-08-27 15:18 ` Will Deacon [this message]
2019-08-27 16:04 ` [PATCH 2/3] arm64: smp: Don't enter kernel with NULL stack pointer or task struct Mark Rutland
2019-08-27 15:18 ` [PATCH 3/3] arm64: smp: Treat unknown boot failures as being 'stuck in kernel' Will Deacon
2019-08-27 15:59 ` Mark Rutland
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