linux-kernel - [PATCH AUTOSEL 5.10 22/45] riscv: cacheinfo: Fix using smp_processor

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Date:   Tue, 19 Jan 2021 20:25:39 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Kefeng Wang <wangkefeng.wang@...wei.com>,
        Atish Patra <atish.patra@....com>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>,
        Sasha Levin <sashal@...nel.org>,
        linux-riscv@...ts.infradead.org
Subject: [PATCH AUTOSEL 5.10 22/45] riscv: cacheinfo: Fix using smp_processor_id() in preemptible

From: Kefeng Wang <wangkefeng.wang@...wei.com>

[ Upstream commit 80709af7325d179b433817f421c85449f2454046 ]

Use raw_smp_processor_id instead of smp_processor_id() to fix warning,

BUG: using smp_processor_id() in preemptible [00000000] code: init/1
caller is debug_smp_processor_id+0x1c/0x26
CPU: 0 PID: 1 Comm: init Not tainted 5.10.0-rc4 #211
Call Trace:
  walk_stackframe+0x0/0xaa
  show_stack+0x32/0x3e
  dump_stack+0x76/0x90
  check_preemption_disabled+0xaa/0xac
  debug_smp_processor_id+0x1c/0x26
  get_cache_size+0x18/0x68
  load_elf_binary+0x868/0xece
  bprm_execve+0x224/0x498
  kernel_execve+0xdc/0x142
  run_init_process+0x90/0x9e
  try_to_run_init_process+0x12/0x3c
  kernel_init+0xb4/0xf8
  ret_from_exception+0x0/0xc

The issue is found when CONFIG_DEBUG_PREEMPT enabled.

Reviewed-by: Atish Patra <atish.patra@....com>
Tested-by: Atish Patra <atish.patra@....com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
[Palmer: Added a comment.]
Signed-off-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/riscv/kernel/cacheinfo.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/cacheinfo.c b/arch/riscv/kernel/cacheinfo.c
index de59dd457b415..d867813570442 100644
--- a/arch/riscv/kernel/cacheinfo.c
+++ b/arch/riscv/kernel/cacheinfo.c
@@ -26,7 +26,16 @@ cache_get_priv_group(struct cacheinfo *this_leaf)
 
 static struct cacheinfo *get_cacheinfo(u32 level, enum cache_type type)
 {
-	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(smp_processor_id());
+	/*
+	 * Using raw_smp_processor_id() elides a preemptability check, but this
+	 * is really indicative of a larger problem: the cacheinfo UABI assumes
+	 * that cores have a homonogenous view of the cache hierarchy.  That
+	 * happens to be the case for the current set of RISC-V systems, but
+	 * likely won't be true in general.  Since there's no way to provide
+	 * correct information for these systems via the current UABI we're
+	 * just eliding the check for now.
+	 */
+	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(raw_smp_processor_id());
 	struct cacheinfo *this_leaf;
 	int index;
 
-- 
2.27.0