MIPS: preserve scalar FP CSR when switching vector context (b8340673) · Commits · 戴 / test

Switching the vector context implicitly saves & restores the state of the aliased scalar FP data registers, however the scalar FP control & status register is distinct from the MSA control & status register. In order to allow scalar FP to function correctly in programs using MSA, the scalar CSR needs to be saved & restored along with the MSA vector context. Signed-off-by:

Paul Burton <paul.burton@imgtec.com> Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/7301/ Signed-off-by:

Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/r4k_switch.S

+3 −1

Original line number	Diff line number	Diff line
		@@ -64,8 +64,10 @@
		/* Check whether we're saving scalar or vector context. */
		bgtz a3, 1f

		/* Save 128b MSA vector context. */
		/* Save 128b MSA vector context + scalar FP control & status. */
		cfc1 t1, fcr31
		msa_save_all a0
		sw t1, THREAD_FCR31(a0)
		b 2f

		1: /* Save 32b/64b scalar FP context. */

arch/mips/kernel/traps.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -1154,6 +1154,11 @@ static int enable_restore_fp_context(int msa)

		/* We need to restore the vector context. */
		restore_msa(current);

		/* Restore the scalar FP control & status register */
		if (!was_fpu_owner)
		asm volatile("ctc1 %0, $31" : : "r"(current->thread.fpu.fcr31));

		return 0;
		}

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