Module Name: src
Committed By: maxv
Date: Sun Aug 21 10:07:15 UTC 2016
Modified Files:
src/sys/arch/amd64/amd64: gdt.c
Log Message:
Explain a little what we are doing. Also, make sure gdt_init_cpu is called
on the currently running CPU. Theoretically, we could put the same KASSERT
in gdt_reload_cpu, but the associated IPI is never sent, which is another
issue.
To generate a diff of this commit:
cvs rdiff -u -r1.31 -r1.32 src/sys/arch/amd64/amd64/gdt.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/amd64/amd64/gdt.c
diff -u src/sys/arch/amd64/amd64/gdt.c:1.31 src/sys/arch/amd64/amd64/gdt.c:1.32
--- src/sys/arch/amd64/amd64/gdt.c:1.31 Sun Aug 21 08:30:22 2016
+++ src/sys/arch/amd64/amd64/gdt.c Sun Aug 21 10:07:15 2016
@@ -1,4 +1,4 @@
-/* $NetBSD: gdt.c,v 1.31 2016/08/21 08:30:22 christos Exp $ */
+/* $NetBSD: gdt.c,v 1.32 2016/08/21 10:07:15 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 1.31 2016/08/21 08:30:22 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: gdt.c,v 1.32 2016/08/21 10:07:15 maxv Exp $");
#include "opt_multiprocessor.h"
#include "opt_xen.h"
@@ -105,7 +105,8 @@ set_sys_gdt(int slot, void *base, size_t
}
/*
- * Initialize the GDT.
+ * Initialize the GDT. We already have a gdtstore, which was temporarily used
+ * by the bootstrap code. Now, we allocate a new gdtstore, and put it in cpu0.
*/
void
gdt_init(void)
@@ -120,11 +121,18 @@ gdt_init(void)
gdt_next = 0;
gdt_free = GNULL_SEL;
gdt_dynavail =
- (gdt_size - DYNSEL_START) / sizeof (struct sys_segment_descriptor);
+ (gdt_size - DYNSEL_START) / sizeof(struct sys_segment_descriptor);
old_gdt = gdtstore;
+
+ /* Allocate MAXGDTSIZ bytes of virtual memory. */
gdtstore = (char *)uvm_km_alloc(kernel_map, MAXGDTSIZ, 0,
UVM_KMF_VAONLY);
+
+ /*
+ * Allocate only MINGDTSIZ bytes of physical memory. We will grow this
+ * area in gdt_grow at run-time if needed.
+ */
for (va = (vaddr_t)gdtstore; va < (vaddr_t)gdtstore + MINGDTSIZ;
va += PAGE_SIZE) {
pg = uvm_pagealloc(NULL, 0, NULL, UVM_PGA_ZERO);
@@ -135,17 +143,21 @@ gdt_init(void)
VM_PROT_READ | VM_PROT_WRITE, 0);
}
pmap_update(pmap_kernel());
+
+ /* Copy the initial bootstrap GDT into the new area. */
memcpy(gdtstore, old_gdt, DYNSEL_START);
ci->ci_gdt = (void *)gdtstore;
#ifndef XEN
set_sys_segment(GDT_ADDR_SYS(gdtstore, GLDT_SEL), ldtstore,
LDT_SIZE - 1, SDT_SYSLDT, SEL_KPL, 0);
#endif
+
gdt_init_cpu(ci);
}
/*
- * Allocate shadow GDT for a slave CPU.
+ * Allocate shadow GDT for a secondary CPU. It contains the same values as the
+ * GDT present in cpu0 (gdtstore).
*/
void
gdt_alloc_cpu(struct cpu_info *ci)
@@ -157,6 +169,7 @@ gdt_alloc_cpu(struct cpu_info *ci)
ci->ci_gdt = (union descriptor *)uvm_km_alloc(kernel_map, max_len,
0, UVM_KMF_VAONLY);
+
for (va = (vaddr_t)ci->ci_gdt; va < (vaddr_t)ci->ci_gdt + min_len;
va += PAGE_SIZE) {
while ((pg = uvm_pagealloc(NULL, 0, NULL, UVM_PGA_ZERO))
@@ -167,20 +180,22 @@ gdt_alloc_cpu(struct cpu_info *ci)
VM_PROT_READ | VM_PROT_WRITE, 0);
}
pmap_update(pmap_kernel());
+
memset(ci->ci_gdt, 0, min_len);
memcpy(ci->ci_gdt, gdtstore, gdt_size);
}
-
/*
- * Load appropriate gdt descriptor; we better be running on *ci
- * (for the most part, this is how a CPU knows who it is).
+ * Load appropriate GDT descriptor into the currently running CPU, which must
+ * be ci.
*/
void
gdt_init_cpu(struct cpu_info *ci)
{
struct region_descriptor region;
+ KASSERT(curcpu() == ci);
+
#ifndef XEN
setregion(®ion, ci->ci_gdt, (uint16_t)(MAXGDTSIZ - 1));
#else
@@ -206,7 +221,9 @@ gdt_reload_cpu(struct cpu_info *ci)
#if !defined(XEN) || defined(USER_LDT)
/*
- * Grow the GDT.
+ * Grow the GDT. The GDT is present on each CPU, so we need to iterate over all
+ * of them. We already have the virtual memory, we only need to grow the
+ * physical memory.
*/
static void
gdt_grow(void)
@@ -305,10 +322,13 @@ tss_alloc(struct x86_64_tss *tss)
int slot;
mutex_enter(&cpu_lock);
+
slot = gdt_get_slot();
- set_sys_gdt(slot, tss, sizeof (struct x86_64_tss) - 1,
- SDT_SYS386TSS, SEL_KPL, 0);
+ set_sys_gdt(slot, tss, sizeof(struct x86_64_tss) - 1, SDT_SYS386TSS,
+ SEL_KPL, 0);
+
mutex_exit(&cpu_lock);
+
return GDYNSEL(slot, SEL_KPL);
#else /* XEN */
/* TSS, what for? */
