This is a note to let you know that I've just added the patch titled
x86, apic: Handle a bad TSC more gracefully
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-apic-handle-a-bad-tsc-more-gracefully.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b47dcbdc5161d3d5756f430191e2840d9b855492 Mon Sep 17 00:00:00 2001
From: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Date: Wed, 15 Oct 2014 10:12:07 -0700
Subject: x86, apic: Handle a bad TSC more gracefully
From: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxx>
Cc: Bandan Das <bsd@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/e2fa274e498c33988efac0ba8b7e3120f7f92d78.1413393027.git.luto@xxxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/apic/apic.c | 4 ++--
arch/x86/kernel/tsc.c | 5 ++++-
2 files changed, 6 insertions(+), 3 deletions(-)
--- 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
--- 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;
}
Patches currently in stable-queue which might be from luto@xxxxxxxxxxxxxx are
queue-3.14/mnt-prevent-pivot_root-from-creating-a-loop-in-the-mount-tree.patch
queue-3.14/x86-apic-handle-a-bad-tsc-more-gracefully.patch
queue-3.14/fs-allow-open-dir-o_tmpfile-...-0-with-mode-0.patch
queue-3.14/x86_64-entry-filter-rflags.nt-on-entry-from-userspace.patch
queue-3.14/x86_64-entry-fix-out-of-bounds-read-on-sysenter.patch
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