patch-1.3.55 linux/include/asm-alpha/mmu_context.h

• Lines: 59
• Date: Sat Jan 6 14:30:11 1996
• Orig file: v1.3.54/linux/include/asm-alpha/mmu_context.h
• Orig date: Thu Jan 1 02:00:00 1970

diff -u --recursive --new-file v1.3.54/linux/include/asm-alpha/mmu_context.h linux/include/asm-alpha/mmu_context.h
@@ -0,0 +1,58 @@
+#ifndef __ALPHA_MMU_CONTEXT_H
+#define __ALPHA_MMU_CONTEXT_H
+
+/*
+ * get a new mmu context..
+ *
+ * Copyright (C) 1996, Linus Torvalds
+ */
+
+#include <asm/pgtable.h>
+
+/*
+ * The maximum ASN's the processor supports. On the EV4 this doesn't
+ * matter as the pal-code doesn't use the ASNs anyway, on the EV5
+ * EV5 this is 127.
+ */
+#define MAX_ASN 127
+
+#define ASN_VERSION_SHIFT 32
+#define ASN_VERSION_MASK ((~0UL) << ASN_VERSION_SHIFT)
+#define ASN_FIRST_VERSION (1UL << ASN_VERSION_SHIFT)
+
+/*
+ * NOTE! The way this is set up, the high bits of the "asn_cache" (and
+ * the "mm->context") are the ASN _version_ code. A version of 0 is
+ * always considered invalid, so to invalidate another process you only
+ * need to do "p->mm->context = 0".
+ *
+ * If we need more ASN's than the processor has, we invalidate the old
+ * user TLB's (tbiap()) and start a new ASN version. That will automatically
+ * force a new asn for any other processes the next time they want to
+ * run.
+ */
+extern inline void get_mmu_context(struct task_struct *p)
+{
+	static unsigned long asn_cache = ASN_FIRST_VERSION;
+	struct mm_struct * mm = p->mm;
+	unsigned long asn = mm->context;
+
+	/* Check if our ASN is of an older version and thus invalid */
+	if ((asn_cache ^ asn) & ASN_VERSION_MASK) {
+		/* get a new asn of the current version */
+		asn = asn_cache++;
+		/* check if it's legal.. */
+		if ((asn & ~ASN_VERSION_MASK) > MAX_ASN) {
+			/* start a new version, invalidate all old asn's */
+			tbiap();
+			asn_cache = (asn_cache & ASN_VERSION_MASK) + ASN_FIRST_VERSION;
+			if (!asn_cache)
+				asn_cache = ASN_FIRST_VERSION;
+			asn = asn_cache++;
+		}
+		mm->context = asn;			/* full version + asn */
+		p->tss.asn = asn & ~ASN_VERSION_MASK;	/* just asn */
+	}
+}
+
+#endif