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authorAndy Lutomirski <luto@amacapital.net>2014-10-15 10:12:07 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-11-14 09:00:10 -0800
commit09eea6d2a92e092897d6767988e21186d2ed781e (patch)
tree184237428dcc369eaf23ba2a9b8b961a8415a927
parenteeae838b835b6ffb7ac7f6bcbc800488a61f873b (diff)
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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 <luto@amacapital.net> Cc: Bandan Das <bsd@redhat.com> Link: http://lkml.kernel.org/r/e2fa274e498c33988efac0ba8b7e3120f7f92d78.1413393027.git.luto@amacapital.net Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/x86/kernel/apic/apic.c4
-rw-r--r--arch/x86/kernel/tsc.c5
2 files changed, 6 insertions, 3 deletions
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;
}