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From:   Xiao Liang <xiliang@redhat.com>
To:     tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org,
        Xiao Liang <xiliang@redhat.com>
Subject: [PATCH v1 1/1] perf/x86/amd/power: do not load amd power module in intel platform
Date:   Mon, 22 Jan 2018 14:12:52 +0800
Message-Id: <20180122061252.6394-1-xiliang@redhat.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

"power" module can be loaded if it is not amd processor.

And user cannot unload it after loaded it. The following call trace generated
when tried to unload it.

 BUG: unable to handle kernel NULL pointer dereference at           (null)
 IP: __list_del_entry_valid+0x29/0x90
 PGD 0 P4D 0
 Oops: 0000 [#1] SMP PTI
 CPU: 1 PID: 26046 Comm: modprobe Not tainted 4.14.13-300.fc27.x86_64 #1
 Hardware name: Xen HVM domU, BIOS 4.9.1 12/12/2017
 task: ffff9a138f8dddc0 task.stack: ffffb0ec41cbc000
 RIP: 0010:__list_del_entry_valid+0x29/0x90

 Call Trace:
  perf_pmu_unregister+0x25/0xf0
  amd_power_pmu_exit+0x1c/0xd23 [power]
  SyS_delete_module+0x1a8/0x2b0
  ? exit_to_usermode_loop+0x8f/0xb0
  entry_SYSCALL_64_fastpath+0x20/0x83
 RIP: 0033:0x7fb67d78e5c7

Signed-off-by: Xiao Liang <xiliang@redhat.com>
---
 arch/x86/events/amd/power.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/events/amd/power.c b/arch/x86/events/amd/power.c
index a6eee5ac4f58..2aefacf5c5b2 100644
--- a/arch/x86/events/amd/power.c
+++ b/arch/x86/events/amd/power.c
@@ -277,7 +277,7 @@ static int __init amd_power_pmu_init(void)
 	int ret;
 
 	if (!x86_match_cpu(cpu_match))
-		return 0;
+		return -ENODEV;
 
 	if (!boot_cpu_has(X86_FEATURE_ACC_POWER))
 		return -ENODEV;
-- 
2.14.3