From 17f6bac2249356c795339e03a0742cd79be3cab8 Mon Sep 17 00:00:00 2001 From: Chuanhua Lei Date: Thu, 6 Sep 2018 18:03:23 +0800 Subject: [PATCH] x86/tsc: Prevent result truncation on 32bit Loops per jiffy is calculated by multiplying tsc_khz with 1e3 and then dividing it by HZ. Both tsc_khz and the temporary variable holding the multiplication result are of type unsigned long, so on 32bit the result is truncated to the lower 32bit. Use u64 as type for the temporary variable and cast tsc_khz to it before multiplying. [ tglx: Massaged changelog and removed pointless braces ] Fixes: cf7a63ef4e02 ("x86/tsc: Calibrate tsc only once") Signed-off-by: Chuanhua Lei Signed-off-by: Thomas Gleixner Cc: yixin.zhu@linux.intel.com Cc: "H. Peter Anvin" Cc: Peter Zijlstra Cc: Len Brown Cc: Pavel Tatashin Cc: Rajvi Jingar Cc: Dou Liyang Link: https://lkml.kernel.org/r/1536228203-18701-1-git-send-email-chuanhua.lei@linux.intel.com --- arch/x86/kernel/tsc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 1463468..6490f61 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -1415,7 +1415,7 @@ static bool __init determine_cpu_tsc_frequencies(bool early) static unsigned long __init get_loops_per_jiffy(void) { - unsigned long lpj = tsc_khz * KHZ; + u64 lpj = (u64)tsc_khz * KHZ; do_div(lpj, HZ); return lpj; -- 2.7.4