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

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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