linux-kernel - [PATCH] perf/x86/intel/pt: Test CPU vendor before loading

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Message-Id: <1447325772-4799-1-git-send-email-bp@alien8.de>
Date:	Thu, 12 Nov 2015 11:56:12 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] perf/x86/intel/pt: Test CPU vendor before loading

From: Borislav Petkov <bp@...e.de>

This keeps poking at MSR 0x570 when loading, i.e. MSR_IA32_RTIT_CTL,
which is most likely not present on other vendors. It is using the _safe
variant but there's no need to try it at all, really. Besides, it causes
unhandled rdmsr warnings when booting in a guest:

 kvm [4414]: vcpu0 unhandled rdmsr: 0x570

So check CPU vendor before doing anything else.

Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Paul Gortmaker <paul.gortmaker@...driver.com>
Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/kernel/cpu/perf_event_intel_pt.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/cpu/perf_event_intel_pt.c b/arch/x86/kernel/cpu/perf_event_intel_pt.c
index 42169283448b..fa1262b025e7 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_pt.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_pt.c
@@ -1129,6 +1129,9 @@ static __init int pt_init(void)
 {
 	int ret, cpu, prior_warn = 0;
 
+	if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
+		return 0;
+
 	BUILD_BUG_ON(sizeof(struct topa) > PAGE_SIZE);
 	get_online_cpus();
 	for_each_online_cpu(cpu) {
-- 
2.3.5

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