Subversion Repositories planix.SVN

#include	<u.h>

#include	<ureg.h>

#include	"../port/lib.h"

#include	"mem.h"

#include	"dat.h"

#include	"fns.h"

/*

 *	We have one page table per processor.

 *

 *	Different processes are distinguished via the VSID field in

 *	the segment registers.  As flushing the entire page table is an

 *	expensive operation, we implement an aging algorithm for

 *	mmu pids, with a background kproc to purge stale pids en mass.

 *

 *	This needs modifications to run on a multiprocessor.

 */

static ulong	ptabsize;			/* number of bytes in page table */

static ulong	ptabmask;		/* hash mask */

/*

 *	VSID is 24 bits.  3 are required to distinguish segments in user

 *	space (kernel space only uses the BATs).  pid 0 is reserved.

 *	The top 2 bits of the pid are used as a `color' for the background

 *	pid reclamation algorithm.

 */

enum {

	PIDBASE = 1,

	PIDBITS = 21,

	COLBITS = 2,

	PIDMAX = ((1<<PIDBITS)-1),

	COLMASK = ((1<<COLBITS)-1),

};

#define	VSID(pid, i)	(((pid)<<3)|i)

#define	PIDCOLOR(pid)	((pid)>>(PIDBITS-COLBITS))

#define	PTECOL(color)	PTE0(1, VSID(((color)<<(PIDBITS-COLBITS)), 0), 0, 0)

void

mmuinit(void)

{

	int lhash, mem, i;

	ulong memsize;

	memsize = conf.npage * BY2PG;

	if(ptabsize == 0) {

		/* heuristically size the hash table */

		lhash = 10;

		mem = (1<<23);

		while(mem < memsize) {

			lhash++;

			mem <<= 1;

		}

		ptabsize = (1<<(lhash+6));

		ptabmask = (1<<lhash)-1;

	}

	m->ptabbase = (ulong)xspanalloc(ptabsize, 0, ptabsize);

	/* set page table base address */

	putsdr1(PADDR(m->ptabbase) | (ptabmask>>10));

	m->mmupid = PIDBASE;

	m->sweepcolor = 0;

	m->trigcolor = COLMASK;

	for(i = 0; i < 16; i++)

		putsr(i<<28, 0);

}

static int

work(void*)

{

	return PIDCOLOR(m->mmupid) == m->trigcolor;

}

void

mmusweep(void*)

{

	Proc *p;

	int i, x, sweepcolor;

	ulong *ptab, *ptabend, ptecol;

	for(;;) {

		if(PIDCOLOR(m->mmupid) != m->trigcolor)

			sleep(&m->sweepr, work, nil);

		sweepcolor = m->sweepcolor;

		x = splhi();

		p = proctab(0);

		for(i = 0; i < conf.nproc; i++, p++)

			if(PIDCOLOR(p->mmupid) == sweepcolor)

				p->mmupid = 0;

		splx(x);

		ptab = (ulong*)m->ptabbase;

		ptabend = (ulong*)(m->ptabbase+ptabsize);

		ptecol = PTECOL(sweepcolor);

		while(ptab < ptabend) {

			if((*ptab & PTECOL(3)) == ptecol){

				*ptab = 0;

			}

			ptab += 2;

		}

		m->sweepcolor = (sweepcolor+1) & COLMASK;

		m->trigcolor = (m->trigcolor+1) & COLMASK;

	}

}

int

newmmupid(void)

{

	int pid, newcolor, i, x;

	Proc *p;

	pid = m->mmupid++;

	if(m->mmupid > PIDMAX){

		/* Used up all mmupids, start again from first.  Flush the tlb

		 * to delete any entries with old pids remaining, then reassign

		 * all pids.

		 */

		m->mmupid = PIDBASE;

		x = splhi();

		tlbflushall();

		p = proctab(0);

		for(i = 0; i < conf.nproc; i++, p++)

			p->mmupid = 0;

		splx(x);

		wakeup(&m->sweepr);

	}

	newcolor = PIDCOLOR(m->mmupid);

	if(newcolor != PIDCOLOR(pid)) {

		if(newcolor == m->sweepcolor) {

			/* desperation time.  can't block here.  punt to fault/putmmu */

			print("newmmupid: %uld: no free mmu pids\n", up->pid);

			if(m->mmupid == PIDBASE)

				m->mmupid = PIDMAX;

			else

				m->mmupid--;

			pid = 0;

		}

		else if(newcolor == m->trigcolor)

			wakeup(&m->sweepr);

	}

	up->mmupid = pid;

	return pid;

}

void

flushmmu(void)

{

	int x;

	x = splhi();

	up->newtlb = 1;

	mmuswitch(up);

	splx(x);

}

/*

 * called with splhi

 */

void

mmuswitch(Proc *p)

{

	int i, mp;

	ulong r;

	if(p->kp) {

		for(i = 0; i < 8; i++)

			putsr(i<<28, 0);

		return;

	}

	if(p->newtlb) {

		p->mmupid = 0;

		p->newtlb = 0;

	}

	mp = p->mmupid;

	if(mp == 0)

		mp = newmmupid();

	for(i = 0; i < 8; i++){

		r = VSID(mp, i)|BIT(1)|BIT(2);

		putsr(i<<28, r);

	}

}

void

mmurelease(Proc* p)

{

	p->mmupid = 0;

}

void

putmmu(ulong va, ulong pa, Page *pg)

{

	int mp;

	char *ctl;

	ulong *p, *ep, *q, pteg;

	ulong vsid, hash;

	ulong ptehi, x;

	static ulong pva;

	/*

	 *	If mmupid is 0, mmuswitch/newmmupid was unable to assign us

	 *	a pid, hence we faulted.  Keep calling sched() until the mmusweep

	 *	proc catches up, and we are able to get a pid.

	 */

	while((mp = up->mmupid) == 0)

		sched();

	vsid = VSID(mp, va>>28);

	hash = (vsid ^ ((va>>12)&0xffff)) & ptabmask;

	ptehi = PTE0(1, vsid, 0, va);

	pteg = m->ptabbase + BY2PTEG*hash;

	p = (ulong*)pteg;

	ep = (ulong*)(pteg+BY2PTEG);

	q = nil;

	while(p < ep) {

		x = p[0];

		if(x == ptehi) {

			q = p;

			break;

		}

		if(q == nil && (x & BIT(0)) == 0)

			q = p;

		p += 2;

	}

	if(q == nil) {

		q = (ulong*)(pteg+m->slotgen);

		m->slotgen = (m->slotgen + BY2PTE) & (BY2PTEG-1);

	}

	if (q[0] != ptehi || q[1] != pa){

		tlbflush(va);

		m->tlbpurge++;

	}

	q[0] = ptehi;

	q[1] = pa;

	ctl = &pg->cachectl[m->machno];

	switch(*ctl) {

	case PG_NEWCOL:

	default:

		panic("putmmu: %d\n", *ctl);

		break;

	case PG_TXTFLUSH:

		dcflush((void*)pg->va, BY2PG);

		icflush((void*)pg->va, BY2PG);

		*ctl = PG_NOFLUSH;

		break;

	case PG_NOFLUSH:

		break;

	}

}

void

checkmmu(ulong, ulong)

{

}

void

countpagerefs(ulong*, int)

{

}

/*

 * Return the number of bytes that can be accessed via KADDR(pa).

 * If pa is not a valid argument to KADDR, return 0.

 */

ulong

cankaddr(ulong pa)

{

	if(pa >= -KZERO)

		return 0;

	return -KZERO - pa;

}