ARM: vfp: fix vfp_sync_state() (54cb3dbb) · Commits · 戴 / test

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>

arch/arm/vfp/vfpmodule.c

+16 −20

Original line number	Diff line number	Diff line
		@@ -444,32 +444,28 @@ void vfp_sync_state(struct thread_info *thread)
		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])
		goto out;
		if (last_VFP_context[cpu] == &thread->vfpstate) {
		u32 fpexc = fmrx(FPEXC);

		/*
		* Save the last VFP state on this CPU.
		*/
		fmxr(FPEXC, fpexc \| FPEXC_EN);
		vfp_save_state(last_VFP_context[cpu], fpexc);
		fmxr(FPEXC, fpexc);
		vfp_save_state(&thread->vfpstate, fpexc \| FPEXC_EN);
		fmxr(FPEXC, fpexc & ~FPEXC_EN);

		/*
		* Set the context to NULL to force a reload the next time the thread
		* uses the VFP.
		* 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

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