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Commit 061da3df authored by Michael Holzheu's avatar Michael Holzheu Committed by Martin Schwidefsky
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s390/kernel: Fix smp_call_ipl_cpu() for offline CPUs 



If the IPL CPU is offline, currently the pcpu_delegate() function
used by smp_call_ipl_cpu() does not work because pcpu_delegate()
modifies the lowcore of the target CPU. In case of an offline
IPL CPU currently the prefix register is zero but pcpu->lowcore
still points to the old prefix page. Therefore the lowcore changes
done by pcpu_delegate() have no effect.

With this fix pcpu_delegate() now uses memcpy_absolute() and therefore
also prepares the absolute zero lowcore if the target CPU has prefix
register zero.

Signed-off-by: default avatarMichael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 73bf463e

arch/s390/kernel/smp.c

+10 −9
Original line number Diff line number Diff line
@@ -297,26 +297,27 @@ static void pcpu_start_fn(struct pcpu *pcpu, void (*func)(void *), void *data) 
static void pcpu_delegate(struct pcpu *pcpu, void (*func)(void *),

			  void *data, unsigned long stack)

{

	struct _lowcore *lc = pcpu->lowcore;

	unsigned short this_cpu;

	struct _lowcore *lc = lowcore_ptr[pcpu - pcpu_devices];

	struct {

		unsigned long	stack;

		void		*func;

		void		*data;

		unsigned long	source;

	} restart = { stack, func, data, stap() };



	__load_psw_mask(psw_kernel_bits);

	this_cpu = stap();

	if (pcpu->address == this_cpu)

	if (pcpu->address == restart.source)

		func(data);	/* should not return */

	/* Stop target cpu (if func returns this stops the current cpu). */

	pcpu_sigp_retry(pcpu, sigp_stop, 0);

	/* Restart func on the target cpu and stop the current cpu. */

	lc->restart_stack = stack;

	lc->restart_fn = (unsigned long) func;

	lc->restart_data = (unsigned long) data;

	lc->restart_source = (unsigned long) this_cpu;

	memcpy_absolute(&lc->restart_stack, &restart, sizeof(restart));

	asm volatile(

		"0:	sigp	0,%0,6	# sigp restart to target cpu\n"

		"	brc	2,0b	# busy, try again\n"

		"1:	sigp	0,%1,5	# sigp stop to current cpu\n"

		"	brc	2,1b	# busy, try again\n"

		: : "d" (pcpu->address), "d" (this_cpu) : "0", "1", "cc");

		: : "d" (pcpu->address), "d" (restart.source) : "0", "1", "cc");

	for (;;) ;

}