linux-kernel - [PATCH 5.10 20/83] riscv: Flush current cpu icache before other cpus

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Message-Id: <20211011134509.059155260@linuxfoundation.org>
Date:   Mon, 11 Oct 2021 15:45:40 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Alexandre Ghiti <alex@...ti.fr>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>
Subject: [PATCH 5.10 20/83] riscv: Flush current cpu icache before other cpus

From: Alexandre Ghiti <alex@...ti.fr>

commit bb8958d5dc79acbd071397abb57b8756375fe1ce upstream.

On SiFive Unmatched, I recently fell onto the following BUG when booting:

[    0.000000] ftrace: allocating 36610 entries in 144 pages
[    0.000000] Oops - illegal instruction [#1]
[    0.000000] Modules linked in:
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.13.1+ #5
[    0.000000] Hardware name: SiFive HiFive Unmatched A00 (DT)
[    0.000000] epc : riscv_cpuid_to_hartid_mask+0x6/0xae
[    0.000000]  ra : __sbi_rfence_v02+0xc8/0x10a
[    0.000000] epc : ffffffff80007240 ra : ffffffff80009964 sp : ffffffff81803e10
[    0.000000]  gp : ffffffff81a1ea70 tp : ffffffff8180f500 t0 : ffffffe07fe30000
[    0.000000]  t1 : 0000000000000004 t2 : 0000000000000000 s0 : ffffffff81803e60
[    0.000000]  s1 : 0000000000000000 a0 : ffffffff81a22238 a1 : ffffffff81803e10
[    0.000000]  a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000
[    0.000000]  a5 : 0000000000000000 a6 : ffffffff8000989c a7 : 0000000052464e43
[    0.000000]  s2 : ffffffff81a220c8 s3 : 0000000000000000 s4 : 0000000000000000
[    0.000000]  s5 : 0000000000000000 s6 : 0000000200000100 s7 : 0000000000000001
[    0.000000]  s8 : ffffffe07fe04040 s9 : ffffffff81a22c80 s10: 0000000000001000
[    0.000000]  s11: 0000000000000004 t3 : 0000000000000001 t4 : 0000000000000008
[    0.000000]  t5 : ffffffcf04000808 t6 : ffffffe3ffddf188
[    0.000000] status: 0000000200000100 badaddr: 0000000000000000 cause: 0000000000000002
[    0.000000] [<ffffffff80007240>] riscv_cpuid_to_hartid_mask+0x6/0xae
[    0.000000] [<ffffffff80009474>] sbi_remote_fence_i+0x1e/0x26
[    0.000000] [<ffffffff8000b8f4>] flush_icache_all+0x12/0x1a
[    0.000000] [<ffffffff8000666c>] patch_text_nosync+0x26/0x32
[    0.000000] [<ffffffff8000884e>] ftrace_init_nop+0x52/0x8c
[    0.000000] [<ffffffff800f051e>] ftrace_process_locs.isra.0+0x29c/0x360
[    0.000000] [<ffffffff80a0e3c6>] ftrace_init+0x80/0x130
[    0.000000] [<ffffffff80a00f8c>] start_kernel+0x5c4/0x8f6
[    0.000000] ---[ end trace f67eb9af4d8d492b ]---
[    0.000000] Kernel panic - not syncing: Attempted to kill the idle task!
[    0.000000] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]---

While ftrace is looping over a list of addresses to patch, it always failed
when patching the same function: riscv_cpuid_to_hartid_mask. Looking at the
backtrace, the illegal instruction is encountered in this same function.
However, patch_text_nosync, after patching the instructions, calls
flush_icache_range. But looking at what happens in this function:

flush_icache_range -> flush_icache_all
                   -> sbi_remote_fence_i
                   -> __sbi_rfence_v02
                   -> riscv_cpuid_to_hartid_mask

The icache and dcache of the current cpu are never synchronized between the
patching of riscv_cpuid_to_hartid_mask and calling this same function.

So fix this by flushing the current cpu's icache before asking for the other
cpus to do the same.

Signed-off-by: Alexandre Ghiti <alex@...ti.fr>
Fixes: fab957c11efe ("RISC-V: Atomic and Locking Code")
Cc: stable@...r.kernel.org
Signed-off-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/riscv/mm/cacheflush.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/riscv/mm/cacheflush.c
+++ b/arch/riscv/mm/cacheflush.c
@@ -16,6 +16,8 @@ static void ipi_remote_fence_i(void *inf
 
 void flush_icache_all(void)
 {
+	local_flush_icache_all();
+
 	if (IS_ENABLED(CONFIG_RISCV_SBI))
 		sbi_remote_fence_i(NULL);
 	else