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Commit 8a95408e authored by Eduardo Habkost's avatar Eduardo Habkost Committed by Ingo Molnar
Browse files

xen64: Clear %fs on xen_load_tls() 



We need to do this, otherwise we can get a GPF on hypercall return
after TLS descriptor is cleared but %fs is still pointing to it.

Signed-off-by: default avatarEduardo Habkost <ehabkost@redhat.com>
Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.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 4a5c3e77

arch/x86/xen/enlighten.c

+22 −9
Original line number Diff line number Diff line
@@ -364,14 +364,6 @@ static void load_TLS_descriptor(struct thread_struct *t, 


static void xen_load_tls(struct thread_struct *t, unsigned int cpu)

{

	xen_mc_batch();



	load_TLS_descriptor(t, cpu, 0);

	load_TLS_descriptor(t, cpu, 1);

	load_TLS_descriptor(t, cpu, 2);



	xen_mc_issue(PARAVIRT_LAZY_CPU);



	/*

	 * XXX sleazy hack: If we're being called in a lazy-cpu zone,

	 * it means we're in a context switch, and %gs has just been
@@ -380,9 +372,30 @@ static void xen_load_tls(struct thread_struct *t, unsigned int cpu) 
	 * Either way, it has been saved, and the new value will get

	 * loaded properly.  This will go away as soon as Xen has been

	 * modified to not save/restore %gs for normal hypercalls.

	 *

	 * On x86_64, this hack is not used for %gs, because gs points

	 * to KERNEL_GS_BASE (and uses it for PDA references), so we

	 * must not zero %gs on x86_64

	 *

	 * For x86_64, we need to zero %fs, otherwise we may get an

	 * exception between the new %fs descriptor being loaded and

	 * %fs being effectively cleared at __switch_to().

	 */

	if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_CPU)

	if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_CPU) {

#ifdef CONFIG_X86_32

		loadsegment(gs, 0);

#else

		loadsegment(fs, 0);

#endif

	}



	xen_mc_batch();



	load_TLS_descriptor(t, cpu, 0);

	load_TLS_descriptor(t, cpu, 1);

	load_TLS_descriptor(t, cpu, 2);



	xen_mc_issue(PARAVIRT_LAZY_CPU);

}



#ifdef CONFIG_X86_64