Commit 4d681be3 authored Apr 05, 2013 by konrad@kernel.org Committed by H. Peter Anvin Apr 11, 2013

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>

parent 357d1226

arch/x86/power/cpu.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -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