zynq: introduce SG_FAULT to prevent access to AXI segment while PL is not ready

access to the axi segment hangs the machine when the fpga
is not programmed yet. to prevent access, we introduce a
new SG_FAULT flag, that when set on the Segment.type or
Physseg.attr, causes the fault handler to immidiately
return with an error (as if the segment would not be mapped).

during programming, we temporarily set the SG_FAULT flag
on the axi physseg, flush all processes tlb's that have
the segment mapped and when programming is done, we clear
the flag again.

sys/src/9/pc/devlml.c

@@ -179,7 +179,7 @@ lmlreset(void)
 		kstrdup(&segbuf.name, name);
 		segbuf.pa = PADDR(lml->codedata);
 		segbuf.size = Codedatasize;
-		if(addphysseg(&segbuf) == -1){
+		if(addphysseg(&segbuf) == nil){
 			print("lml: physsegment: %s\n", name);
 			return;
 		}
@@ -190,7 +190,7 @@ lmlreset(void)
 		kstrdup(&segbuf.name, name);
 		segbuf.pa = (ulong)regpa;
 		segbuf.size = pcidev->mem[0].size;
-		if(addphysseg(&segbuf) == -1){
+		if(addphysseg(&segbuf) == nil){
 			print("lml: physsegment: %s\n", name);
 			return;
 		}

sys/src/9/port/devsegment.c

@@ -232,7 +232,7 @@ segmentcreate(Chan *c, char *name, int omode, ulong perm)
 	if(TYPE(c) != Qtopdir)
 		error(Eperm);
 
-	if(isphysseg(name))
+	if(findphysseg(name) != nil)
 		error(Eexist);
 
 	if((perm & DMDIR) == 0)

sys/src/9/port/fault.c

@@ -10,7 +10,7 @@ fault(uintptr addr, int read)
 {
 	Segment *s;
 	char *sps;
-	int pnd;
+	int pnd, attr;
 
 	if(up == nil)
 		panic("fault: nil up");
@@ -34,7 +34,10 @@ fault(uintptr addr, int read)
 			return -1;
 		}
 
-		if(!read && (s->type&SG_RONLY)) {
+		attr = s->type;
+		if((attr & SG_TYPE) == SG_PHYSICAL)
+			attr |= s->pseg->attr;
+		if((attr & SG_FAULT) != 0 || !read && (attr & SG_RONLY) != 0) {
 			qunlock(s);
 			up->psstate = sps;
 			return -1;
@@ -62,15 +65,16 @@ faulterror(char *s, Chan *c)
 {
 	char buf[ERRMAX];
 
-	if(c != nil && c->path != nil){
-		snprint(buf, sizeof buf, "%s accessing %s: %s", s, c->path->s, up->errstr);
-		s = buf;
-	}
+	if(c != nil)
+		snprint(buf, sizeof buf, "sys: %s accessing %s: %s", s, chanpath(c), up->errstr);
+	else
+		snprint(buf, sizeof buf, "sys: %s", s);
 	if(up->nerrlab) {
 		if(up->kp == 0)
-			postnote(up, 1, s, NDebug);
+			postnote(up, 1, buf, NDebug);
 		error(s);
 	}
+	pprint("suicide: %s\n", buf);
 	pexit(s, 1);
 }
 
@@ -208,13 +212,12 @@ fixfault(Segment *s, uintptr addr, int read)
 		*pte = etp = ptealloc();
 
 	pg = &etp->pages[(soff&(PTEMAPMEM-1))/BY2PG];
-	type = s->type&SG_TYPE;
-
 	if(pg < etp->first)
 		etp->first = pg;
 	if(pg > etp->last)
 		etp->last = pg;
 
+	type = s->type & SG_TYPE;
 	switch(type) {
 	default:
 		panic("fault");

sys/src/9/port/portdat.h

@@ -377,6 +377,7 @@ enum
 
 	SG_RONLY	= 0040,		/* Segment is read only */
 	SG_CEXEC	= 0100,		/* Detach at exec */
+	SG_FAULT	= 0200,		/* Fault on access */
 };
 
 #define PG_ONSWAP	1

sys/src/9/port/portfns.h

@@ -1,7 +1,7 @@
 void		_assert(char*);
 void		accounttime(void);
 Timer*		addclock0link(void (*)(void), int);
-int		addphysseg(Physseg*);
+Physseg*	addphysseg(Physseg*);
 void		addbootfile(char*, uchar*, ulong);
 void		addwatchdog(Watchdog*);
 Block*		adjustblock(Block*, int);
@@ -141,7 +141,7 @@ void		isdir(Chan*);
 int		iseve(void);
 int		islo(void);
 Segment*	isoverlap(Proc*, uintptr, uintptr);
-int		isphysseg(char*);
+Physseg*	findphysseg(char*);
 void		ixsummary(void);
 void		kickpager(void);
 void		killbig(char*);
@@ -231,6 +231,7 @@ void		procctl(void);
 void		procdump(void);
 int		procfdprint(Chan*, int, char*, int);
 void		procflushseg(Segment*);
+void		procflushpseg(Physseg*);
 int		procindex(ulong);
 void		procinit0(void);
 ulong		procpagecount(Proc*);

sys/src/9/port/proc.c

@@ -1321,35 +1321,30 @@ procdump(void)
 }
 
 /*
- *  wait till all processes have flushed their mmu
- *  state about segement s
+ *  wait till all matching processes have flushed their mmu
  */
-void
-procflushseg(Segment *s)
+static void
+procflushmmu(int (*match)(Proc*, void*), void *a)
 {
-	int i, ns, nm, nwait;
+	int i, nm, nwait;
 	Proc *p;
 
 	/*
-	 *  tell all processes with this
-	 *  segment to flush their mmu's
+	 *  tell all matching processes to flush their mmu's
 	 */
 	nwait = 0;
 	for(i=0; i<conf.nproc; i++) {
 		p = &procalloc.arena[i];
-		if(p->state == Dead)
-			continue;
-		for(ns = 0; ns < NSEG; ns++)
-			if(p->seg[ns] == s){
-				p->newtlb = 1;
-				for(nm = 0; nm < conf.nmach; nm++){
-					if(MACHP(nm)->proc == p){
-						MACHP(nm)->flushmmu = 1;
-						nwait++;
-					}
+		if(p->state != Dead && (*match)(p, a)){
+			p->newtlb = 1;
+			for(nm = 0; nm < conf.nmach; nm++){
+				if(MACHP(nm)->proc == p){
+					MACHP(nm)->flushmmu = 1;
+					nwait++;
 				}
-				break;
 			}
+			break;
+		}
 	}
 
 	if(nwait == 0)
@@ -1364,6 +1359,42 @@ procflushseg(Segment *s)
 			sched();
 }
 
+static int
+matchseg(Proc *p, void *a)
+{
+	int ns;
+
+	for(ns = 0; ns < NSEG; ns++){
+		if(p->seg[ns] == a)
+			return 1;
+	}
+	return 0;
+}
+void
+procflushseg(Segment *s)
+{
+	procflushmmu(matchseg, s);
+}
+
+static int
+matchpseg(Proc *p, void *a)
+{
+	Segment *s;
+	int ns;
+
+	for(ns = 0; ns < NSEG; ns++){
+		s = p->seg[ns];
+		if(s != nil && s->pseg == a)
+			return 1;
+	}
+	return 0;
+}
+void
+procflushpseg(Physseg *ps)
+{
+	procflushmmu(matchpseg, ps);
+}
+
 void
 scheddump(void)
 {

sys/src/9/port/segment.c

@@ -551,7 +551,7 @@ isoverlap(Proc *p, uintptr va, uintptr len)
 	return nil;
 }
 
-int
+Physseg*
 addphysseg(Physseg* new)
 {
 	Physseg *ps;
@@ -564,34 +564,29 @@ addphysseg(Physseg* new)
 	for(ps = physseg; ps->name; ps++){
 		if(strcmp(ps->name, new->name) == 0){
 			unlock(&physseglock);
-			return -1;
+			return nil;
 		}
 	}
 	if(ps-physseg >= nelem(physseg)-2){
 		unlock(&physseglock);
-		return -1;
+		return nil;
 	}
 	*ps = *new;
 	unlock(&physseglock);
 
-	return 0;
+	return ps;
 }
 
-int
-isphysseg(char *name)
+Physseg*
+findphysseg(char *name)
 {
 	Physseg *ps;
-	int rv = 0;
 
-	lock(&physseglock);
-	for(ps = physseg; ps->name; ps++){
-		if(strcmp(ps->name, name) == 0){
-			rv = 1;
-			break;
-		}
-	}
-	unlock(&physseglock);
-	return rv;
+	for(ps = physseg; ps->name; ps++)
+		if(strcmp(ps->name, name) == 0)
+			return ps;
+
+	return nil;
 }
 
 uintptr
@@ -654,12 +649,10 @@ segattach(Proc *p, ulong attr, char *name, uintptr va, uintptr len)
 	if(isoverlap(p, va, len) != nil)
 		error(Esoverlap);
 
-	for(ps = physseg; ps->name; ps++)
-		if(strcmp(name, ps->name) == 0)
-			goto found;
+	ps = findphysseg(name);
+	if(ps == nil)
+		error(Ebadarg);
 
-	error(Ebadarg);
-found:
 	if(len > ps->size)
 		error(Enovmem);
 

sys/src/9/ppc/m8260.c

@@ -445,7 +445,7 @@ addseg(char *name, ulong start, ulong length)
 	kstrdup(&segbuf.name, name);
 	segbuf.pa = start;
 	segbuf.size = length;
-	if (addphysseg(&segbuf) == -1) {
+	if (addphysseg(&segbuf) == nil) {
 		print("addphysseg: %s\n", name);
 		return;
 	}

sys/src/9/zynq/devarch.c

@@ -25,14 +25,15 @@ static Dirtab archdir[Qmax] = {
 };
 static int narchdir = Qbase;
 
-int temp = -128;
-ulong *devc;
-int dmadone;
+static int temp = -128;
+static ulong *devc;
+static int dmadone;
 enum { PLBUFSIZ = 8192 };
-uchar *plbuf;
-Rendez plinitr, pldoner, pldmar;
-QLock plrlock, plwlock;
-Ref plwopen;
+static uchar *plbuf;
+static Rendez plinitr, pldoner, pldmar;
+static QLock plrlock, plwlock;
+static Ref plwopen;
+static Physseg *axi;
 
 enum {
 	DEVCTRL = 0,
@@ -164,6 +165,8 @@ plirq(Ureg *, void *)
 		slcr[0x900/4] = 0xf;
 		slcr[0x240/4] = 0;
 		devc[DEVMASK] |= DONE;
+		if(axi != nil)
+			axi->attr &= ~SG_FAULT;
 		wakeup(&pldoner);
 	}
 	if((fl & DMADONE) != 0){
@@ -187,16 +190,21 @@ plinit(void)
 	slcr[FPGA0_CLK_CTRL] = 1<<20 | 10<<8;
 
 	memset(&seg, 0, sizeof seg);
-	seg.attr = SG_PHYSICAL;
+	seg.attr = SG_PHYSICAL | SG_FAULT;
 	seg.name = "axi";
 	seg.pa = 0x40000000;
 	seg.size = 0x8000000;
-	addphysseg(&seg);
+	axi = addphysseg(&seg);
 }
 
 static void
 plconf(void)
 {
+	if(axi != nil){
+		axi->attr |= SG_FAULT;
+		procflushpseg(axi);
+	}
+
 	slcr[0x240/4] = 0xf;
 	slcr[0x900/4] = 0xa;
 	devc[DEVISTS] = DONE|INITPE|DMADONE;