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Commit 478de5a9 authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge Committed by Ingo Molnar
Browse files

x86: save %fs and %gs before load_TLS() and arch_leave_lazy_cpu_mode() 



We must do this because load_TLS() may need to clear %fs and %gs.
(e.g. under Xen).

Signed-off-by: default avatarEduardo Habkost <ehabkost@redhat.com>
Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: xen-devel <xen-devel@lists.xensource.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 3fe0a63e

arch/x86/kernel/process_64.c

+11 −6
Original line number Diff line number Diff line
@@ -538,6 +538,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) 
				 *next = &next_p->thread;

	int cpu = smp_processor_id();

	struct tss_struct *tss = &per_cpu(init_tss, cpu);

	unsigned fsindex, gsindex;



	/* we're going to use this soon, after a few expensive things */

	if (next_p->fpu_counter>5)
@@ -560,6 +561,15 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) 
	if (unlikely(next->ds | prev->ds))

		loadsegment(ds, next->ds);





	/* We must save %fs and %gs before load_TLS() because

	 * %fs and %gs may be cleared by load_TLS().

	 *

	 * (e.g. xen_load_tls())

	 */

	savesegment(fs, fsindex);

	savesegment(gs, gsindex);



	load_TLS(next, cpu);



	/*
@@ -575,8 +585,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) 
	 * Switch FS and GS.

	 */

	{ 

		unsigned fsindex;

		savesegment(fs, fsindex);

		/* segment register != 0 always requires a reload. 

		   also reload when it has changed. 

		   when prev process used 64bit base always reload
@@ -594,10 +602,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) 
		if (next->fs) 

			wrmsrl(MSR_FS_BASE, next->fs); 

		prev->fsindex = fsindex;

	}

	{ 

		unsigned gsindex;

		savesegment(gs, gsindex);



		if (unlikely(gsindex | next->gsindex | prev->gs)) {

			load_gs_index(next->gsindex);

			if (gsindex)