From 09eea6d2a92e092897d6767988e21186d2ed781e Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Wed, 15 Oct 2014 10:12:07 -0700 Subject: x86, apic: Handle a bad TSC more gracefully commit b47dcbdc5161d3d5756f430191e2840d9b855492 upstream. If the TSC is unusable or disabled, then this patch fixes: - Confusion while trying to clear old APIC interrupts. - Division by zero and incorrect programming of the TSC deadline timer. This fixes boot if the CPU has a TSC deadline timer but a missing or broken TSC. The failure to boot can be observed with qemu using -cpu qemu64,-tsc,+tsc-deadline This also happens to me in nested KVM for unknown reasons. With this patch, I can boot cleanly (although without a TSC). Signed-off-by: Andy Lutomirski Cc: Bandan Das Link: http://lkml.kernel.org/r/e2fa274e498c33988efac0ba8b7e3120f7f92d78.1413393027.git.luto@amacapital.net Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/apic/apic.c | 4 ++-- arch/x86/kernel/tsc.c | 5 ++++- 2 files changed, 6 insertions(+), 3 deletions(-) (limited to 'arch') diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index 7f26c9a70a9e..523f147b2470 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -1290,7 +1290,7 @@ void setup_local_APIC(void) unsigned int value, queued; int i, j, acked = 0; unsigned long long tsc = 0, ntsc; - long long max_loops = cpu_khz; + long long max_loops = cpu_khz ? cpu_khz : 1000000; if (cpu_has_tsc) rdtscll(tsc); @@ -1387,7 +1387,7 @@ void setup_local_APIC(void) break; } if (queued) { - if (cpu_has_tsc) { + if (cpu_has_tsc && cpu_khz) { rdtscll(ntsc); max_loops = (cpu_khz << 10) - (ntsc - tsc); } else diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index e0d1d7a8354e..de0290605903 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -1173,14 +1173,17 @@ void __init tsc_init(void) x86_init.timers.tsc_pre_init(); - if (!cpu_has_tsc) + if (!cpu_has_tsc) { + setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER); return; + } tsc_khz = x86_platform.calibrate_tsc(); cpu_khz = tsc_khz; if (!tsc_khz) { mark_tsc_unstable("could not calculate TSC khz"); + setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER); return; } -- cgit v1.2.3