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x86, wakeup, sleep: Use pvops functions for changing GDT entries 

We check the TSS descriptor before we try to dereference it.
Also we document what the value '9' actually means using the
AMD64 Architecture Programmer's Manual Volume 2, pg 90:
"Hex value 9: Available 64-bit TSS" and pg 91:
"The available 32-bit TSS (09h), which is redefined as the
available 64-bit TSS."

Without this, on Xen, where the GDT is available as R/O (to
protect the hypervisor from the guest modifying it), we end up
with a pagetable fault.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Link: http://lkml.kernel.org/r/1365194544-14648-5-git-send-email-konrad.wilk@oracle.com
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
konrad@kernel.org 2013-04-05 16:42:24 -04:00 committed by H. Peter Anvin
parent 357d122670
commit 4d681be3c3
1 changed files with 7 additions and 2 deletions
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9
arch/x86/power/cpu.c
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@ -132,7 +132,10 @@ static void fix_processor_context(void)
{
int cpu = smp_processor_id();
struct tss_struct *t = &per_cpu(init_tss, cpu);
#ifdef CONFIG_X86_64
struct desc_struct *desc = get_cpu_gdt_table(cpu);
tss_desc tss;
#endif
set_tss_desc(cpu, t); /*
* This just modifies memory; should not be
* necessary. But... This is necessary, because
@ -141,7 +144,9 @@ static void fix_processor_context(void)
*/
#ifdef CONFIG_X86_64
get_cpu_gdt_table(cpu)[GDT_ENTRY_TSS].type = 9;
memcpy(&tss, &desc[GDT_ENTRY_TSS], sizeof(tss_desc));
tss.type = 0x9; /* The available 64-bit TSS (see AMD vol 2, pg 91 */
write_gdt_entry(desc, GDT_ENTRY_TSS, &tss, DESC_TSS);
syscall_init(); /* This sets MSR_*STAR and related */
#endif