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| author | Eduardo Habkost <ehabkost@redhat.com> | 2008-07-09 00:07:10 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-07-16 11:04:55 +0200 |
| commit | 8a95408e183b3e4aaf3b6a66fa34bff4db53011b (patch) | |
| tree | af3d69d791d65fe324d4883fbe6a2e3d5f065fd0 /arch/x86/xen | |
| parent | xen64: implement failsafe callback (diff) | |
| download | linux-8a95408e183b3e4aaf3b6a66fa34bff4db53011b.tar.xz linux-8a95408e183b3e4aaf3b6a66fa34bff4db53011b.zip | |
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: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Jeremy 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: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/xen')
| -rw-r--r-- | arch/x86/xen/enlighten.c | 31 |
1 files changed, 22 insertions, 9 deletions
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index 0172ba774523..c13698faae54 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -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 |