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[src/trunk]: src/sys/arch/amd64/amd64 Use a bitmap-based allocator, will be e...



details:   https://anonhg.NetBSD.org/src/rev/9ed8415c6d25
branches:  trunk
changeset: 352317:9ed8415c6d25
user:      maxv <maxv%NetBSD.org@localhost>
date:      Sat Mar 25 15:05:16 2017 +0000

description:
Use a bitmap-based allocator, will be easier to share with i386.

diffstat:

 sys/arch/amd64/amd64/gdt.c |  101 ++++++++++++++++----------------------------
 1 files changed, 36 insertions(+), 65 deletions(-)

diffs (202 lines):

diff -r 79dd1696940c -r 9ed8415c6d25 sys/arch/amd64/amd64/gdt.c
--- a/sys/arch/amd64/amd64/gdt.c        Sat Mar 25 13:24:08 2017 +0000
+++ b/sys/arch/amd64/amd64/gdt.c        Sat Mar 25 15:05:16 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: gdt.c,v 1.37 2017/02/08 18:50:51 kre Exp $     */
+/*     $NetBSD: gdt.c,v 1.38 2017/03/25 15:05:16 maxv Exp $    */
 
 /*-
  * Copyright (c) 1996, 1997, 2009 The NetBSD Foundation, Inc.
@@ -37,7 +37,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: gdt.c,v 1.37 2017/02/08 18:50:51 kre Exp $");
+__KERNEL_RCSID(0, "$NetBSD: gdt.c,v 1.38 2017/03/25 15:05:16 maxv Exp $");
 
 #include "opt_multiprocessor.h"
 #include "opt_xen.h"
@@ -57,16 +57,20 @@
 #include <xen/hypervisor.h>
 #endif
 
-int gdt_size;          /* size of GDT in bytes */
-int gdt_dyncount;      /* number of dyn. allocated GDT entries in use */
-int gdt_dynavail;
-int gdt_next;          /* next available slot for sweeping */
-int gdt_free;          /* next free slot; terminated with GNULL_SEL */
+#define NDYNSLOTS \
+       ((MAXGDTSIZ - DYNSEL_START) / sizeof(struct sys_segment_descriptor))
+
+typedef struct {
+       bool busy[NDYNSLOTS];
+       size_t nslots;
+} gdt_bitmap_t;
+
+size_t gdt_size;                       /* size of GDT in bytes */              
+static gdt_bitmap_t gdt_bitmap;                /* bitmap of busy slots */
 
 #if defined(USER_LDT) || !defined(XEN)
 static void set_sys_gdt(int, void *, size_t, int, int, int);
 #endif
-void gdt_init(void);
 
 void
 update_descriptor(void *tp, void *ep)
@@ -83,7 +87,7 @@
 
        if (!pmap_extract_ma(pmap_kernel(), (vaddr_t)table, &pa) ||
            HYPERVISOR_update_descriptor(pa, *entry))
-               panic("HYPERVISOR_update_descriptor failed\n");
+               panic("HYPERVISOR_update_descriptor failed");
 #endif
 }
 
@@ -124,11 +128,10 @@
        vaddr_t va;
        struct cpu_info *ci = &cpu_info_primary;
 
+       /* Initialize the global values */
        gdt_size = MINGDTSIZ;
-       gdt_dyncount = 0;
-       gdt_next = 0;
-       gdt_free = GNULL_SEL;
-       gdt_dynavail =
+       memset(&gdt_bitmap.busy, 0, sizeof(gdt_bitmap.busy));
+       gdt_bitmap.nslots =
            (gdt_size - DYNSEL_START) / sizeof(struct sys_segment_descriptor);
 
        old_gdt = gdtstore;
@@ -228,10 +231,10 @@
        vaddr_t va;
 
        old_size = gdt_size;
-       gdt_size <<= 1;
+       gdt_size *= 2;
        if (gdt_size > MAXGDTSIZ)
                gdt_size = MAXGDTSIZ;
-       gdt_dynavail =
+       gdt_bitmap.nslots =
            (gdt_size - DYNSEL_START) / sizeof(struct sys_segment_descriptor);
 
        for (CPU_INFO_FOREACH(cii, ci)) {
@@ -250,57 +253,34 @@
        pmap_update(pmap_kernel());
 }
 
-/*
- * Allocate a GDT slot as follows:
- * 1) If there are entries on the free list, use those.
- * 2) If there are fewer than gdt_dynavail entries in use, there are free slots
- *    near the end that we can sweep through.
- * 3) As a last resort, we increase the size of the GDT, and sweep through
- *    the new slots.
- */
 static int
 gdt_get_slot(void)
 {
-       int slot;
-       struct sys_segment_descriptor *gdt;
-
-       gdt = (struct sys_segment_descriptor *)&gdtstore[DYNSEL_START];
+       size_t i;
 
        KASSERT(mutex_owned(&cpu_lock));
 
-       if (gdt_free != GNULL_SEL) {
-               slot = gdt_free;
-               gdt_free = gdt[slot].sd_xx3;    /* XXXfvdl res. field abuse */
-       } else {
-               KASSERT(gdt_next == gdt_dyncount);
-               if (gdt_next >= gdt_dynavail) {
-                       if (gdt_size >= MAXGDTSIZ)
-                               panic("gdt_get_slot: out of memory");
-                       gdt_grow();
+       while (1) {
+               for (i = 0; i < gdt_bitmap.nslots; i++) {
+                       if (!gdt_bitmap.busy[i]) {
+                               gdt_bitmap.busy[i] = true;
+                               return (int)i;
+                       }
                }
-               slot = gdt_next++;
+               if (gdt_size >= MAXGDTSIZ)
+                       panic("gdt_get_slot: out of memory");
+               gdt_grow();
        }
-
-       gdt_dyncount++;
-       return slot;
+       /* NOTREACHED */
+       return 0;
 }
 
-/*
- * Deallocate a GDT slot, putting it on the free list.
- */
 static void
 gdt_put_slot(int slot)
 {
-       struct sys_segment_descriptor *gdt;
-
        KASSERT(mutex_owned(&cpu_lock));
-
-       gdt = (struct sys_segment_descriptor *)&gdtstore[DYNSEL_START];
-
-       gdt_dyncount--;
-       gdt[slot].sd_type = SDT_SYSNULL;
-       gdt[slot].sd_xx3 = gdt_free;
-       gdt_free = slot;
+       KASSERT(slot < gdt_bitmap.nslots);
+       gdt_bitmap.busy[slot] = false;
 }
 #endif
 
@@ -319,7 +299,7 @@
        mutex_exit(&cpu_lock);
 
        return GDYNSEL(slot, SEL_KPL);
-#else  /* XEN */
+#else
        /* TSS, what for? */
        return GSEL(GNULL_SEL, SEL_KPL);
 #endif
@@ -338,9 +318,6 @@
 }
 
 #ifdef USER_LDT
-/*
- * XXX: USER_LDT is not implemented on amd64.
- */
 int
 ldt_alloc(void *ldtp, size_t len)
 {
@@ -380,25 +357,19 @@
         * Zero out last frame after limit if needed.
         */
        va = desc->rd_base + desc->rd_limit + 1;
-       __PRINTK(("memset 0x%lx -> 0x%lx\n", va, roundup(va, PAGE_SIZE)));
-       memset((void *) va, 0, roundup(va, PAGE_SIZE) - va);
+       memset((void *)va, 0, roundup(va, PAGE_SIZE) - va);
        for (i = 0; i < roundup(desc->rd_limit, PAGE_SIZE) >> PAGE_SHIFT; i++) {
-
                /*
                 * The lgdt instruction uses virtual addresses,
                 * do some translation for Xen.
                 * Mark pages R/O too, else Xen will refuse to use them.
                 */
-
                frames[i] = ((paddr_t) xpmap_ptetomach(
-                               (pt_entry_t *) (desc->rd_base + (i << PAGE_SHIFT))))
-                       >> PAGE_SHIFT;
-               __PRINTK(("frames[%d] = 0x%lx (pa 0x%lx)\n", i, frames[i],
-                   xpmap_mtop(frames[i] << PAGE_SHIFT)));
+                   (pt_entry_t *)(desc->rd_base + (i << PAGE_SHIFT)))) >>
+                   PAGE_SHIFT;
                pmap_pte_clearbits(kvtopte(desc->rd_base + (i << PAGE_SHIFT)),
                    PG_RW);
        }
-       __PRINTK(("HYPERVISOR_set_gdt(%d)\n", (desc->rd_limit + 1) >> 3));
 
        if (HYPERVISOR_set_gdt(frames, (desc->rd_limit + 1) >> 3))
                panic("lgdt(): HYPERVISOR_set_gdt() failed");



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