From c6428464894889e110418928e6b37dc2eb4cee56 Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Wed, 24 Jan 2007 18:47:08 +0100 Subject: [ARM] 4111/1: Allow VFP to work with thread migration on SMP The current lazy saving of the VFP registers is no longer possible with thread migration on SMP. This patch implements a per-CPU vfp-state pointer and the saving of the VFP registers at every context switch. The registers restoring is still performed in a lazy way. Signed-off-by: Catalin Marinas Signed-off-by: Russell King --- arch/arm/vfp/entry.S | 1 + arch/arm/vfp/vfp.h | 4 ++++ arch/arm/vfp/vfphw.S | 26 ++++++++++++++++++++++++-- arch/arm/vfp/vfpmodule.c | 30 ++++++++++++++++++++++++++---- 4 files changed, 55 insertions(+), 6 deletions(-) (limited to 'arch/arm/vfp') diff --git a/arch/arm/vfp/entry.S b/arch/arm/vfp/entry.S index 7b595547c1c8..ca2a5ad19ea6 100644 --- a/arch/arm/vfp/entry.S +++ b/arch/arm/vfp/entry.S @@ -25,6 +25,7 @@ do_vfp: enable_irq ldr r4, .LCvfp + ldr r11, [r10, #TI_CPU] @ CPU number add r10, r10, #TI_VFPSTATE @ r10 = workspace ldr pc, [r4] @ call VFP entry point diff --git a/arch/arm/vfp/vfp.h b/arch/arm/vfp/vfp.h index f2797896e6d5..54a2ad6d9ca2 100644 --- a/arch/arm/vfp/vfp.h +++ b/arch/arm/vfp/vfp.h @@ -370,3 +370,7 @@ struct op { u32 (* const fn)(int dd, int dn, int dm, u32 fpscr); u32 flags; }; + +#ifdef CONFIG_SMP +extern void vfp_save_state(void *location, u32 fpexc); +#endif diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S index e51e6679c402..d4b7b229631d 100644 --- a/arch/arm/vfp/vfphw.S +++ b/arch/arm/vfp/vfphw.S @@ -65,6 +65,7 @@ @ r2 = faulted PC+4 @ r9 = successful return @ r10 = vfp_state union +@ r11 = CPU number @ lr = failure return .globl vfp_support_entry @@ -79,7 +80,7 @@ vfp_support_entry: DBGSTR1 "enable %x", r10 ldr r3, last_VFP_context_address orr r1, r1, #FPEXC_ENABLE @ user FPEXC has the enable bit set - ldr r4, [r3] @ last_VFP_context pointer + ldr r4, [r3, r11, lsl #2] @ last_VFP_context pointer bic r5, r1, #FPEXC_EXCEPTION @ make sure exceptions are disabled cmp r4, r10 beq check_for_exception @ we are returning to the same @@ -91,7 +92,9 @@ vfp_support_entry: @ exceptions, so we can get at the @ rest of it +#ifndef CONFIG_SMP @ Save out the current registers to the old thread state + @ No need for SMP since this is not done lazily DBGSTR1 "save old state %p", r4 cmp r4, #0 @@ -105,10 +108,11 @@ vfp_support_entry: stmia r4, {r1, r5, r6, r8} @ save FPEXC, FPSCR, FPINST, FPINST2 @ and point r4 at the word at the @ start of the register dump +#endif no_old_VFP_process: DBGSTR1 "load state %p", r10 - str r10, [r3] @ update the last_VFP_context pointer + str r10, [r3, r11, lsl #2] @ update the last_VFP_context pointer @ Load the saved state back into the VFP VFPFLDMIA r10 @ reload the working registers while @ FPEXC is in a safe state @@ -162,6 +166,24 @@ process_exception: @ required. If not, the user code will @ retry the faulted instruction +#ifdef CONFIG_SMP + .globl vfp_save_state + .type vfp_save_state, %function +vfp_save_state: + @ Save the current VFP state + @ r0 - save location + @ r1 - FPEXC + DBGSTR1 "save VFP state %p", r0 + VFPFMRX r2, FPSCR @ current status + VFPFMRX r3, FPINST @ FPINST (always there, rev0 onwards) + tst r1, #FPEXC_FPV2 @ is there an FPINST2 to read? + VFPFMRX r12, FPINST2, NE @ FPINST2 if needed - avoids reading + @ nonexistant reg on rev0 + VFPFSTMIA r0 @ save the working registers + stmia r0, {r1, r2, r3, r12} @ save FPEXC, FPSCR, FPINST, FPINST2 + mov pc, lr +#endif + last_VFP_context_address: .word last_VFP_context diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c index 490d9d18a7d1..f1e5951dc721 100644 --- a/arch/arm/vfp/vfpmodule.c +++ b/arch/arm/vfp/vfpmodule.c @@ -28,7 +28,7 @@ void vfp_testing_entry(void); void vfp_support_entry(void); void (*vfp_vector)(void) = vfp_testing_entry; -union vfp_state *last_VFP_context; +union vfp_state *last_VFP_context[NR_CPUS]; /* * Dual-use variable. @@ -41,13 +41,35 @@ static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v) { struct thread_info *thread = v; union vfp_state *vfp; + __u32 cpu = thread->cpu; if (likely(cmd == THREAD_NOTIFY_SWITCH)) { + u32 fpexc = fmrx(FPEXC); + +#ifdef CONFIG_SMP + /* + * On SMP, if VFP is enabled, save the old state in + * case the thread migrates to a different CPU. The + * restoring is done lazily. + */ + if ((fpexc & FPEXC_ENABLE) && last_VFP_context[cpu]) { + vfp_save_state(last_VFP_context[cpu], fpexc); + last_VFP_context[cpu]->hard.cpu = cpu; + } + /* + * Thread migration, just force the reloading of the + * state on the new CPU in case the VFP registers + * contain stale data. + */ + if (thread->vfpstate.hard.cpu != cpu) + last_VFP_context[cpu] = NULL; +#endif + /* * Always disable VFP so we can lazily save/restore the * old state. */ - fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_ENABLE); + fmxr(FPEXC, fpexc & ~FPEXC_ENABLE); return NOTIFY_DONE; } @@ -68,8 +90,8 @@ static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v) } /* flush and release case: Per-thread VFP cleanup. */ - if (last_VFP_context == vfp) - last_VFP_context = NULL; + if (last_VFP_context[cpu] == vfp) + last_VFP_context[cpu] = NULL; return NOTIFY_DONE; } -- cgit v1.2.3