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Commit 6e2ef5e4 authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

s390/time: add support for the TOD clock epoch extension 



The TOD epoch extension adds 8 epoch bits to the TOD clock to provide
a continuous clock after 2042/09/17. The store-clock-extended (STCKE)
instruction will store the epoch index in the first byte of the
16 bytes stored by the instruction. The read_boot_clock64 and the
read_presistent_clock64 functions need to take the additional bits
into account to give the correct result after 2042/09/17.

The clock-comparator register will stay 64 bit wide. The comparison
of the clock-comparator with the TOD clock is limited to bytes
1 to 8 of the extended TOD format. To deal with the overflow problem
due to an epoch change the clock-comparator sign control in CR0 can
be used to switch the comparison of the 64-bit TOD clock with the
clock-comparator to a signed comparison.

The decision between the signed vs. unsigned clock-comparator
comparisons is done at boot time. Only if the TOD clock is in the
second half of a 142 year epoch the signed comparison is used.
This solves the epoch overflow issue as long as the machine is
booted at least once in an epoch.

Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 45be0a02

arch/s390/include/asm/lowcore.h

+24 −24
Original line number Diff line number Diff line
@@ -95,46 +95,46 @@ struct lowcore { 
	__u64	int_clock;			/* 0x0310 */

	__u64	mcck_clock;			/* 0x0318 */

	__u64	clock_comparator;		/* 0x0320 */

	__u64	boot_clock[2];			/* 0x0328 */



	/* Current process. */

	__u64	current_task;			/* 0x0328 */

	__u8	pad_0x318[0x320-0x318];		/* 0x0330 */

	__u64	kernel_stack;			/* 0x0338 */

	__u64	current_task;			/* 0x0338 */

	__u64	kernel_stack;			/* 0x0340 */



	/* Interrupt, panic and restart stack. */

	__u64	async_stack;			/* 0x0340 */

	__u64	panic_stack;			/* 0x0348 */

	__u64	restart_stack;			/* 0x0350 */

	__u64	async_stack;			/* 0x0348 */

	__u64	panic_stack;			/* 0x0350 */

	__u64	restart_stack;			/* 0x0358 */



	/* Restart function and parameter. */

	__u64	restart_fn;			/* 0x0358 */

	__u64	restart_data;			/* 0x0360 */

	__u64	restart_source;			/* 0x0368 */

	__u64	restart_fn;			/* 0x0360 */

	__u64	restart_data;			/* 0x0368 */

	__u64	restart_source;			/* 0x0370 */



	/* Address space pointer. */

	__u64	kernel_asce;			/* 0x0370 */

	__u64	user_asce;			/* 0x0378 */

	__u64	kernel_asce;			/* 0x0378 */

	__u64	user_asce;			/* 0x0380 */



	/*

	 * The lpp and current_pid fields form a

	 * 64-bit value that is set as program

	 * parameter with the LPP instruction.

	 */

	__u32	lpp;				/* 0x0380 */

	__u32	current_pid;			/* 0x0384 */

	__u32	lpp;				/* 0x0388 */

	__u32	current_pid;			/* 0x038c */



	/* SMP info area */

	__u32	cpu_nr;				/* 0x0388 */

	__u32	softirq_pending;		/* 0x038c */

	__u64	percpu_offset;			/* 0x0390 */

	__u64	vdso_per_cpu_data;		/* 0x0398 */

	__u64	machine_flags;			/* 0x03a0 */

	__u32	preempt_count;			/* 0x03a8 */

	__u8	pad_0x03ac[0x03b0-0x03ac];	/* 0x03ac */

	__u64	gmap;				/* 0x03b0 */

	__u32	spinlock_lockval;		/* 0x03b8 */

	__u32	fpu_flags;			/* 0x03bc */

	__u8	pad_0x03c0[0x0400-0x03c0];	/* 0x03c0 */

	__u32	cpu_nr;				/* 0x0390 */

	__u32	softirq_pending;		/* 0x0394 */

	__u64	percpu_offset;			/* 0x0398 */

	__u64	vdso_per_cpu_data;		/* 0x03a0 */

	__u64	machine_flags;			/* 0x03a8 */

	__u32	preempt_count;			/* 0x03b0 */

	__u8	pad_0x03b4[0x03b8-0x03b4];	/* 0x03b4 */

	__u64	gmap;				/* 0x03b8 */

	__u32	spinlock_lockval;		/* 0x03c0 */

	__u32	fpu_flags;			/* 0x03c4 */

	__u8	pad_0x03c8[0x0400-0x03c8];	/* 0x03c8 */



	/* Per cpu primary space access list */

	__u32	paste[16];			/* 0x0400 */

arch/s390/include/asm/setup.h

+2 −0
Original line number Diff line number Diff line
@@ -32,6 +32,7 @@ 
#define MACHINE_FLAG_TLB_GUEST	_BITUL(14)

#define MACHINE_FLAG_NX		_BITUL(15)

#define MACHINE_FLAG_GS		_BITUL(16)

#define MACHINE_FLAG_SCC	_BITUL(17)



#define LPP_MAGIC		_BITUL(31)

#define LPP_PFAULT_PID_MASK	_AC(0xffffffff, UL)
@@ -72,6 +73,7 @@ extern void detect_memory_memblock(void); 
#define MACHINE_HAS_TLB_GUEST	(S390_lowcore.machine_flags & MACHINE_FLAG_TLB_GUEST)

#define MACHINE_HAS_NX		(S390_lowcore.machine_flags & MACHINE_FLAG_NX)

#define MACHINE_HAS_GS		(S390_lowcore.machine_flags & MACHINE_FLAG_GS)

#define MACHINE_HAS_SCC		(S390_lowcore.machine_flags & MACHINE_FLAG_SCC)



/*

 * Console mode. Override with conmode=

arch/s390/include/asm/timex.h

+34 −4
Original line number Diff line number Diff line
@@ -15,6 +15,8 @@ 
/* The value of the TOD clock for 1.1.1970. */

#define TOD_UNIX_EPOCH 0x7d91048bca000000ULL



extern u64 clock_comparator_max;



/* Inline functions for clock register access. */

static inline int set_tod_clock(__u64 time)

{
@@ -126,7 +128,7 @@ static inline unsigned long long local_tick_disable(void) 
	unsigned long long old;



	old = S390_lowcore.clock_comparator;

	S390_lowcore.clock_comparator = -1ULL;

	S390_lowcore.clock_comparator = clock_comparator_max;

	set_clock_comparator(S390_lowcore.clock_comparator);

	return old;

}
@@ -178,20 +180,20 @@ int get_phys_clock(unsigned long long *clock); 
void init_cpu_timer(void);

unsigned long long monotonic_clock(void);



extern u64 sched_clock_base_cc;

extern unsigned char tod_clock_base[16] __aligned(8);



/**

 * get_clock_monotonic - returns current time in clock rate units

 *

 * The caller must ensure that preemption is disabled.

 * The clock and sched_clock_base get changed via stop_machine.

 * The clock and tod_clock_base get changed via stop_machine.

 * Therefore preemption must be disabled when calling this

 * function, otherwise the returned value is not guaranteed to

 * be monotonic.

 */

static inline unsigned long long get_tod_clock_monotonic(void)

{

	return get_tod_clock() - sched_clock_base_cc;

	return get_tod_clock() - *(unsigned long long *) &tod_clock_base[1];

}



/**
@@ -218,4 +220,32 @@ static inline unsigned long long tod_to_ns(unsigned long long todval) 
	return ((todval >> 9) * 125) + (((todval & 0x1ff) * 125) >> 9);

}



/**

 * tod_after - compare two 64 bit TOD values

 * @a: first 64 bit TOD timestamp

 * @b: second 64 bit TOD timestamp

 *

 * Returns: true if a is later than b

 */

static inline int tod_after(unsigned long long a, unsigned long long b)

{

	if (MACHINE_HAS_SCC)

		return (long long) a > (long long) b;

	return a > b;

}



/**

 * tod_after_eq - compare two 64 bit TOD values

 * @a: first 64 bit TOD timestamp

 * @b: second 64 bit TOD timestamp

 *

 * Returns: true if a is later than b

 */

static inline int tod_after_eq(unsigned long long a, unsigned long long b)

{

	if (MACHINE_HAS_SCC)

		return (long long) a >= (long long) b;

	return a >= b;

}



#endif

arch/s390/kernel/asm-offsets.c

+1 −0
Original line number Diff line number Diff line
@@ -158,6 +158,7 @@ int main(void) 
	OFFSET(__LC_LAST_UPDATE_CLOCK, lowcore, last_update_clock);

	OFFSET(__LC_INT_CLOCK, lowcore, int_clock);

	OFFSET(__LC_MCCK_CLOCK, lowcore, mcck_clock);

	OFFSET(__LC_BOOT_CLOCK, lowcore, boot_clock);

	OFFSET(__LC_CURRENT, lowcore, current_task);

	OFFSET(__LC_KERNEL_STACK, lowcore, kernel_stack);

	OFFSET(__LC_ASYNC_STACK, lowcore, async_stack);

arch/s390/kernel/debug.c

+5 −4
Original line number Diff line number Diff line
@@ -866,7 +866,8 @@ static inline void 
debug_finish_entry(debug_info_t * id, debug_entry_t* active, int level,

			int exception)

{

	active->id.stck = get_tod_clock_fast() - sched_clock_base_cc;

	active->id.stck = get_tod_clock_fast() -

		*(unsigned long long *) &tod_clock_base[1];

	active->id.fields.cpuid = smp_processor_id();

	active->caller = __builtin_return_address(0);

	active->id.fields.exception = exception;
@@ -1455,15 +1456,15 @@ int 
debug_dflt_header_fn(debug_info_t * id, struct debug_view *view,

			 int area, debug_entry_t * entry, char *out_buf)

{

	unsigned long sec, usec;

	unsigned long base, sec, usec;

	char *except_str;

	unsigned long caller;

	int rc = 0;

	unsigned int level;



	level = entry->id.fields.level;

	sec = (entry->id.stck >> 12) + (sched_clock_base_cc >> 12);

	sec = sec - (TOD_UNIX_EPOCH >> 12);

	base = (*(unsigned long *) &tod_clock_base[0]) >> 4;

	sec = (entry->id.stck >> 12) + base - (TOD_UNIX_EPOCH >> 12);

	usec = do_div(sec, USEC_PER_SEC);



	if (entry->id.fields.exception)