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arm64/arch_timer: Provide noinstr sched_clock_read() functions

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With the intent to provide local_clock_noinstr(), a variant of
local_clock() that's safe to be called from noinstr code (with the
assumption that any such code will already be non-preemptible),
prepare for things by providing a noinstr sched_clock_read() function.

Specifically, preempt_enable_*() calls out to schedule(), which upsets
noinstr validation efforts.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Kelley <mikelley@microsoft.com>  # Hyper-V
Link: https://lore.kernel.org/r/20230519102715.435618812@infradead.org
This commit is contained in:
Peter Zijlstra 2023-05-19 12:21:02 +02:00
parent c1d26c0f02
commit 24ee7607b2
2 changed files with 41 additions and 21 deletions
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8
arch/arm64/include/asm/arch_timer.h
View File

@ -88,13 +88,7 @@ static inline notrace u64 arch_timer_read_cntvct_el0(void)
#define arch_timer_reg_read_stable(reg) \
({ \
u64 _val; \
\
preempt_disable_notrace(); \
_val = erratum_handler(read_ ## reg)(); \
preempt_enable_notrace(); \
\
_val; \
erratum_handler(read_ ## reg)(); \
})
/*

54
drivers/clocksource/arm_arch_timer.c
View File

@ -191,22 +191,40 @@ u32 arch_timer_reg_read(int access, enum arch_timer_reg reg,
return val;
}
static notrace u64 arch_counter_get_cntpct_stable(void)
static noinstr u64 raw_counter_get_cntpct_stable(void)
{
return __arch_counter_get_cntpct_stable();
}
static notrace u64 arch_counter_get_cntpct(void)
static notrace u64 arch_counter_get_cntpct_stable(void)
{
u64 val;
preempt_disable_notrace();
val = __arch_counter_get_cntpct_stable();
preempt_enable_notrace();
return val;
}
static noinstr u64 arch_counter_get_cntpct(void)
{
return __arch_counter_get_cntpct();
}
static notrace u64 arch_counter_get_cntvct_stable(void)
static noinstr u64 raw_counter_get_cntvct_stable(void)
{
return __arch_counter_get_cntvct_stable();
}
static notrace u64 arch_counter_get_cntvct(void)
static notrace u64 arch_counter_get_cntvct_stable(void)
{
u64 val;
preempt_disable_notrace();
val = __arch_counter_get_cntvct_stable();
preempt_enable_notrace();
return val;
}
static noinstr u64 arch_counter_get_cntvct(void)
{
return __arch_counter_get_cntvct();
}
@ -753,14 +771,14 @@ static int arch_timer_set_next_event_phys(unsigned long evt,
return 0;
}
static u64 arch_counter_get_cnt_mem(struct arch_timer *t, int offset_lo)
static noinstr u64 arch_counter_get_cnt_mem(struct arch_timer *t, int offset_lo)
{
u32 cnt_lo, cnt_hi, tmp_hi;
do {
cnt_hi = readl_relaxed(t->base + offset_lo + 4);
cnt_lo = readl_relaxed(t->base + offset_lo);
tmp_hi = readl_relaxed(t->base + offset_lo + 4);
cnt_hi = __raw_readl(t->base + offset_lo + 4);
cnt_lo = __raw_readl(t->base + offset_lo);
tmp_hi = __raw_readl(t->base + offset_lo + 4);
} while (cnt_hi != tmp_hi);
return ((u64) cnt_hi << 32) | cnt_lo;
@ -1060,7 +1078,7 @@ bool arch_timer_evtstrm_available(void)
return cpumask_test_cpu(raw_smp_processor_id(), &evtstrm_available);
}
static u64 arch_counter_get_cntvct_mem(void)
static noinstr u64 arch_counter_get_cntvct_mem(void)
{
return arch_counter_get_cnt_mem(arch_timer_mem, CNTVCT_LO);
}
@ -1074,6 +1092,7 @@ struct arch_timer_kvm_info *arch_timer_get_kvm_info(void)
static void __init arch_counter_register(unsigned type)
{
u64 (*scr)(void);
u64 start_count;
int width;
@ -1083,21 +1102,28 @@ static void __init arch_counter_register(unsigned type)
if ((IS_ENABLED(CONFIG_ARM64) && !is_hyp_mode_available()) ||
arch_timer_uses_ppi == ARCH_TIMER_VIRT_PPI) {
if (arch_timer_counter_has_wa())
if (arch_timer_counter_has_wa()) {
rd = arch_counter_get_cntvct_stable;
else
scr = raw_counter_get_cntvct_stable;
} else {
rd = arch_counter_get_cntvct;
scr = arch_counter_get_cntvct;
}
} else {
if (arch_timer_counter_has_wa())
if (arch_timer_counter_has_wa()) {
rd = arch_counter_get_cntpct_stable;
else
scr = raw_counter_get_cntpct_stable;
} else {
rd = arch_counter_get_cntpct;
scr = arch_counter_get_cntpct;
}
}
arch_timer_read_counter = rd;
clocksource_counter.vdso_clock_mode = vdso_default;
} else {
arch_timer_read_counter = arch_counter_get_cntvct_mem;
scr = arch_counter_get_cntvct_mem;
}
width = arch_counter_get_width();
@ -1113,7 +1139,7 @@ static void __init arch_counter_register(unsigned type)
timecounter_init(&arch_timer_kvm_info.timecounter,
&cyclecounter, start_count);
sched_clock_register(arch_timer_read_counter, width, arch_timer_rate);
sched_clock_register(scr, width, arch_timer_rate);
}
static void arch_timer_stop(struct clock_event_device *clk)