linux-kernel - [v2 7/9] x86/tsc: use cpuid to determine CPU frequency

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1490368899-877997-8-git-send-email-pasha.tatashin@oracle.com>
Date:   Fri, 24 Mar 2017 11:21:37 -0400
From:   Pavel Tatashin <pasha.tatashin@...cle.com>
To:     x86@...nel.org, linux-kernel@...r.kernel.org, mingo@...hat.com,
        peterz@...radead.org, tglx@...utronix.de, hpa@...or.com
Subject: [v2 7/9] x86/tsc: use cpuid to determine CPU frequency

Newer processors implement cpuid extension to determine CPU frequency
from cpuid. This patch adds a function that can do this early in boot.

Signed-off-by: Pavel Tatashin <pasha.tatashin@...cle.com>
---
 arch/x86/kernel/tsc.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 1c9fc23..58bd575 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -743,14 +743,14 @@ unsigned long native_calibrate_tsc(void)
 	return tsc_khz;
 }
 
-static unsigned long cpu_khz_from_cpuid(void)
+static unsigned long cpu_khz_from_cpuid_early(int vendor, int cpuid_level)
 {
 	unsigned int eax_base_mhz, ebx_max_mhz, ecx_bus_mhz, edx;
 
-	if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
+	if (vendor != X86_VENDOR_INTEL)
 		return 0;
 
-	if (boot_cpu_data.cpuid_level < 0x16)
+	if (cpuid_level < 0x16)
 		return 0;
 
 	eax_base_mhz = ebx_max_mhz = ecx_bus_mhz = edx = 0;
@@ -770,7 +770,9 @@ unsigned long native_calibrate_cpu(void)
 	unsigned long flags, latch, ms, fast_calibrate;
 	int hpet = is_hpet_enabled(), i, loopmin;
 
-	fast_calibrate = cpu_khz_from_cpuid();
+	fast_calibrate = cpu_khz_from_cpuid_early(boot_cpu_data.x86_vendor,
+						  boot_cpu_data.cpuid_level);
+
 	if (fast_calibrate)
 		return fast_calibrate;
 
-- 
1.8.3.1