printk's in cpu_init() might access per-cpu pv_clock before it's
registered. Which might lead to an incorrect last_value value or
big jumps in it depending on current contents of kvm's hv_clock.
Also ftrace by default uses local clock for time-stamping its
records, which might cause access to not yet registered per-cpu
kvmclock during cpu_init() execution:
function_trace_call -> trace_function ->
trace_buffer_lock_reserve -> ring_buffer_lock_reserve ->
rb_reserve_next_event -> rb_time_stamp ->
trace_clock_local -> sched_clock ->
paravirt_sched_clock ->
kvm_clock_read
Fix provides a simplified version of kvm_setup_secondary_clock(),
that could be safely used before cpu_init() and turns off tracing
for its underlying calls to prevent premature access to kvmclock
during its registration. So that any following usage of
sched_clock() would yield correct value.
Signed-off-by: Igor Mammedov <imammedo@xxxxxxxxxx>
---
arch/x86/kernel/kvmclock.c | 11 +++++++++--
arch/x86/kernel/smpboot.c | 2 +-
arch/x86/mm/pageattr.c | 4 ++--
3 files changed, 12 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 3dd37eb..4660b59 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -185,13 +185,20 @@ static void kvm_restore_sched_clock_state(void)
}
#ifdef CONFIG_X86_LOCAL_APIC
-static void __cpuinit kvm_setup_secondary_clock(void)
+static void __cpuinit notrace kvm_setup_secondary_clock(void)
{
/*
* Now that the first cpu already had this clocksource initialized,
* we shouldn't fail.
*/
- WARN_ON(kvm_register_clock("secondary cpu clock"));
+ int cpu = stack_smp_processor_id();
+ int low, high;
+ struct pvclock_vcpu_time_info *src;
+
+ src = &hv_clock[cpu].pvti;
+ low = (int)slow_virt_to_phys(src) | 1;
+ high = ((u64)slow_virt_to_phys(src) >> 32);
+ native_write_msr_safe(msr_kvm_system_time, low, high);
}
#endif
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 9c73b51..5e2b7cb 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -244,8 +244,8 @@ notrace static void __cpuinit start_secondary(void *unused)
* fragile that we want to limit the things done here to the
* most necessary things.
*/
- cpu_init();
x86_cpuinit.early_percpu_clock_init();
+ cpu_init();
preempt_disable();
smp_callin();
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index bb32480..06cabff 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -330,7 +330,7 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long address,
* or when the present bit is not set. Otherwise we would return a
* pointer to a nonexisting mapping.
*/
-pte_t *lookup_address(unsigned long address, unsigned int *level)
+pte_t notrace *lookup_address(unsigned long address, unsigned int *level)
{
pgd_t *pgd = pgd_offset_k(address);
pud_t *pud;
@@ -374,7 +374,7 @@ EXPORT_SYMBOL_GPL(lookup_address);
* unoptimized should increase the testing coverage for
* the more obscure platforms.
*/
-phys_addr_t slow_virt_to_phys(void *__virt_addr)
+phys_addr_t notrace slow_virt_to_phys(void *__virt_addr)
{
unsigned long virt_addr = (unsigned long)__virt_addr;
phys_addr_t phys_addr;
--
1.7.1
--
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