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* This file contains the code to configure and read/write the ia64 performance
* monitoring stuff.
*
* Originaly Written by Ganesh Venkitachalam, IBM Corp.
* Modifications by David Mosberger-Tang, Hewlett-Packard Co.
* Copyright (C) 1999 Ganesh Venkitachalam <venkitac@us.ibm.com>
* Copyright (C) 1999 David Mosberger-Tang <davidm@hpl.hp.com>
*/
#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/smp_lock.h>
#include <asm/errno.h>
#include <asm/hw_irq.h>
#include <asm/processor.h>
#include <asm/system.h>
#include <asm/uaccess.h>
/* Long blurb on how this works:
* We set dcr.pp, psr.pp, and the appropriate pmc control values with
* this. Notice that we go about modifying _each_ task's pt_regs to
* set cr_ipsr.pp. This will start counting when "current" does an
* _rfi_. Also, since each task's cr_ipsr.pp, and cr_ipsr is inherited
* across forks, we do _not_ need additional code on context
* switches. On stopping of the counters we dont need to go about
* changing every task's cr_ipsr back to where it wuz, because we can
* just set pmc[0]=1. But we do it anyways becuase we will probably
* add thread specific accounting later.
*
* The obvious problem with this is that on SMP systems, it is a bit
* of work (when someone wants to do it:-)) - it would be easier if we
* just added code to the context-switch path, but if we wanted to support
* per-thread accounting, the context-switch path might be long unless
* we introduce a flag in the task_struct. Right now, the following code
* will NOT work correctly on MP (for more than one reason:-)).
*
* The short answer is that to make this work on SMP, we would need
* to lock the run queue to ensure no context switches, send
* an IPI to each processor, and in that IPI handler, set processor regs,
* and just modify the psr bit of only the _current_ thread, since we have
* modified the psr bit correctly in the kernel stack for every process
* which is not running. Also, we need pmd arrays per-processor, and
* the READ_PMD command will need to get values off of other processors.
* IPIs are the answer, irrespective of what the question is. Might
* crash on SMP systems without the lock_kernel().
*/
#ifdef CONFIG_PERFMON
#define MAX_PERF_COUNTER 4 /* true for Itanium, at least */
#define WRITE_PMCS_AND_START 0xa0
#define WRITE_PMCS 0xa1
#define READ_PMDS 0xa2
#define STOP_PMCS 0xa3
#define IA64_COUNTER_MASK 0xffffffffffffff6f
#define PERF_OVFL_VAL 0xffffffff
struct perfmon_counter {
unsigned long data;
unsigned long counter_num;
};
unsigned long pmds[MAX_PERF_COUNTER];
struct task_struct *perf_owner=NULL;
asmlinkage unsigned long
sys_perfmonctl (int cmd1, int cmd2, void *ptr)
{
struct perfmon_counter tmp, *cptr = ptr;
unsigned long pmd, cnum, dcr, flags;
struct task_struct *p;
struct pt_regs *regs;
struct perf_counter;
int i;
switch (cmd1) {
case WRITE_PMCS: /* Writes to PMC's and clears PMDs */
case WRITE_PMCS_AND_START: /* Also starts counting */
if (!access_ok(VERIFY_READ, cptr, sizeof(struct perf_counter)*cmd2))
return -EFAULT;
if (cmd2 > MAX_PERF_COUNTER)
return -EFAULT;
if (perf_owner && perf_owner != current)
return -EBUSY;
perf_owner = current;
for (i = 0; i < cmd2; i++, cptr++) {
copy_from_user(&tmp, cptr, sizeof(tmp));
/* XXX need to check validity of counter_num and perhaps data!! */
ia64_set_pmc(tmp.counter_num, tmp.data);
ia64_set_pmd(tmp.counter_num, 0);
pmds[tmp.counter_num - 4] = 0;
}
if (cmd1 == WRITE_PMCS_AND_START) {
local_irq_save(flags);
dcr = ia64_get_dcr();
dcr |= IA64_DCR_PP;
ia64_set_dcr(dcr);
local_irq_restore(flags);
/*
* This is a no can do. It obviously wouldn't
* work on SMP where another process may not
* be blocked at all. We need to put in a perfmon
* IPI to take care of MP systems. See blurb above.
*/
lock_kernel();
for_each_task(p) {
regs = (struct pt_regs *) (((char *)p) + IA64_STK_OFFSET) -1 ;
ia64_psr(regs)->pp = 1;
}
unlock_kernel();
ia64_set_pmc(0, 0);
}
break;
case READ_PMDS:
if (cmd2 > MAX_PERF_COUNTER)
return -EFAULT;
if (!access_ok(VERIFY_WRITE, cptr, sizeof(struct perf_counter)*cmd2))
return -EFAULT;
/* This looks shady, but IMHO this will work fine. This is
* the sequence that I could come up with to avoid races
* with the interrupt handler. See explanation in the
* following comment.
*/
local_irq_save(flags);
__asm__ __volatile__("rsm psr.pp\n");
dcr = ia64_get_dcr();
dcr &= ~IA64_DCR_PP;
ia64_set_dcr(dcr);
local_irq_restore(flags);
/*
* We cannot write to pmc[0] to stop counting here, as
* that particular instruction might cause an overflow
* and the mask in pmc[0] might get lost. I'm _not_
* sure of the hardware behavior here. So we stop
* counting by psr.pp = 0. And we reset dcr.pp to
* prevent an interrupt from mucking up psr.pp in the
* meanwhile. Perfmon interrupts are pended, hence the
* above code should be ok if one of the above instructions
* caused overflows, i.e the interrupt should get serviced
* when we re-enabled interrupts. When I muck with dcr,
* is the irq_save/restore needed?
*/
for (i = 0, cnum = 4;i < MAX_PERF_COUNTER; i++, cnum++, cptr++){
pmd = pmds[i] + (ia64_get_pmd(cnum) & PERF_OVFL_VAL);
put_user(pmd, &cptr->data);
}
local_irq_save(flags);
__asm__ __volatile__("ssm psr.pp");
dcr = ia64_get_dcr();
dcr |= IA64_DCR_PP;
ia64_set_dcr(dcr);
local_irq_restore(flags);
break;
case STOP_PMCS:
ia64_set_pmc(0, 1);
for (i = 0; i < MAX_PERF_COUNTER; ++i)
ia64_set_pmc(i, 0);
local_irq_save(flags);
dcr = ia64_get_dcr();
dcr &= ~IA64_DCR_PP;
ia64_set_dcr(dcr);
local_irq_restore(flags);
/*
* This is a no can do. It obviously wouldn't
* work on SMP where another process may not
* be blocked at all. We need to put in a perfmon
* IPI to take care of MP systems. See blurb above.
*/
lock_kernel();
for_each_task(p) {
regs = (struct pt_regs *) (((char *)p) + IA64_STK_OFFSET) - 1;
ia64_psr(regs)->pp = 0;
}
unlock_kernel();
perf_owner = NULL;
break;
default:
break;
}
return 0;
}
static inline void
update_counters (void)
{
unsigned long mask, i, cnum, val;
mask = ia64_get_pmc(0) >> 4;
for (i = 0, cnum = 4; i < MAX_PERF_COUNTER; cnum++, i++, mask >>= 1) {
if (mask & 0x1)
val = PERF_OVFL_VAL;
else
/* since we got an interrupt, might as well clear every pmd. */
val = ia64_get_pmd(cnum) & PERF_OVFL_VAL;
pmds[i] += val;
ia64_set_pmd(cnum, 0);
}
}
static void
perfmon_interrupt (int irq, void *arg, struct pt_regs *regs)
{
update_counters();
ia64_set_pmc(0, 0);
ia64_srlz_d();
}
void
perfmon_init (void)
{
if (request_irq(PERFMON_IRQ, perfmon_interrupt, 0, "perfmon", NULL)) {
printk("perfmon_init: could not allocate performance monitor vector %u\n",
PERFMON_IRQ);
return;
}
ia64_set_pmv(PERFMON_IRQ);
ia64_srlz_d();
printk("Initialized perfmon vector to %u\n",PERFMON_IRQ);
}
#else /* !CONFIG_PERFMON */
asmlinkage unsigned long
sys_perfmonctl (int cmd1, int cmd2, void *ptr)
{
return -ENOSYS;
}
#endif /* !CONFIG_PERFMON */
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