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.

1 files changed, 14 insertions, 21 deletions

diff --git a/sys/src/9/port/segment.c b/sys/src/9/port/segment.c
index e9e8959df..e257e47b3 100644
--- a/sys/src/9/port/segment.c
+++ b/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);