Chris Wright wrote:
* Zachary Amsden ([EMAIL PROTECTED]) wrote:
This change encapsulates descriptor and task register management.
These will need some merging together, will take a stab tomorrow.
--- linux-2.6.12-xen0-arch.orig/include/asm-i386/desc.h
+++ linux-2.6.12-xen0-arch/include/asm-i386/desc.h
@@ -14,9 +14,6 @@
static inline void __set_tss_desc(unsigned int cpu, unsigned int entry, void
*addr)
{
- _set_tssldt_desc(&per_cpu(cpu_gdt_table, cpu)[entry], (int)addr,
+ _set_tssldt_desc(&get_cpu_gdt_table(cpu)[entry], (int)addr,
What is Xen doing for the GDT on SMP? Does Xen have 16 pages of GDT per
CPU?
+++ linux-2.6.12-xen0-arch/include/asm-i386/mach-default/mach_desc.h
@@ -0,0 +1,57 @@
+#ifndef __ASM_MACH_DESC_H
+#define __ASM_MACH_DESC_H
+
+extern struct desc_struct cpu_gdt_table[GDT_ENTRIES];
+DECLARE_PER_CPU(struct desc_struct, cpu_gdt_table[GDT_ENTRIES]);
+#define get_cpu_gdt_table(_cpu) per_cpu(cpu_gdt_table, cpu)
+
+#define _set_tssldt_desc(n,addr,limit,type) \
+__asm__ __volatile__ ("movw %w3,0(%2)\n\t" \
+ "movw %%ax,2(%2)\n\t" \
+ "rorl $16,%%eax\n\t" \
+ "movb %%al,4(%2)\n\t" \
+ "movb %4,5(%2)\n\t" \
+ "movb $0,6(%2)\n\t" \
+ "movb %%ah,7(%2)\n\t" \
+ "rorl $16,%%eax" \
+ : "=m"(*(n)) : "a" (addr), "r"(n), "ir"(limit), "i"(type))
This actually doesn't need to move into sub-arch. You can redefine the
call sites (set_ldt_desc / set_tss_desc) to operate on stack (implicit
register) values instead and then notify the hypervisor about GDT
updates. Course, which way is cleaner looks still TBD.
+static inline void clear_LDT(void)
+{
+ int cpu = get_cpu();
+
+ set_ldt_desc(cpu, &default_ldt[0], 5);
+ load_LDT_desc();
+ put_cpu();
+}
+
+/*
+ * load one particular LDT into the current CPU
+ */
+static inline void load_LDT_nolock(mm_context_t *pc, int cpu)
+{
+ void *segments = pc->ldt;
+ int count = pc->size;
+
+ if (likely(!count)) {
+ segments = &default_ldt[0];
+ count = 5;
+ }
+
+ set_ldt_desc(cpu, segments, count);
+ load_LDT_desc();
+}
+
+#endif
These two don't actually need to move into sub-arch ; they can call
functions that have already moved.
So far looks like we are pretty much on the same page, with mostly
cosmetic differences.
Zach
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