ARM: vfp: fix vfp_sync_state()
The more I look at vfp_sync_state(), the more I believe it's trying
to do its job in a really obscure way.
Essentially, last_VFP_context[] tracks who owns the state in the VFP
hardware. If last_VFP_context[] is the context for the thread which
we're interested in, then the VFP hardware has context which is not
saved in the software state - so we need to bring the software state
up to date.
If last_VFP_context[] is for some other thread, we really don't care
what state the VFP hardware is in; it doesn't contain any information
pertinent to the thread we're trying to deal with - so don't touch
the hardware.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index f60a540..86a57ae 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -444,32 +444,28 @@
void vfp_sync_state(struct thread_info *thread)
{
unsigned int cpu = get_cpu();
- u32 fpexc = fmrx(FPEXC);
/*
- * If VFP is enabled, the previous state was already saved and
- * last_VFP_context updated.
+ * If the thread we're interested in is the current owner of the
+ * hardware VFP state, then we need to save its state.
*/
- if (fpexc & FPEXC_EN)
- goto out;
+ if (last_VFP_context[cpu] == &thread->vfpstate) {
+ u32 fpexc = fmrx(FPEXC);
- if (!last_VFP_context[cpu])
- goto out;
+ /*
+ * Save the last VFP state on this CPU.
+ */
+ fmxr(FPEXC, fpexc | FPEXC_EN);
+ vfp_save_state(&thread->vfpstate, fpexc | FPEXC_EN);
+ fmxr(FPEXC, fpexc & ~FPEXC_EN);
- /*
- * Save the last VFP state on this CPU.
- */
- fmxr(FPEXC, fpexc | FPEXC_EN);
- vfp_save_state(last_VFP_context[cpu], fpexc);
- fmxr(FPEXC, fpexc);
+ /*
+ * Set the context to NULL to force a reload the next time
+ * the thread uses the VFP.
+ */
+ last_VFP_context[cpu] = NULL;
+ }
- /*
- * Set the context to NULL to force a reload the next time the thread
- * uses the VFP.
- */
- last_VFP_context[cpu] = NULL;
-
-out:
put_cpu();
}
#endif
