[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 <catalin.marinas@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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412489af76
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c642846489
5 changed files with 58 additions and 6 deletions
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@ -25,6 +25,7 @@
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do_vfp:
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enable_irq
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ldr r4, .LCvfp
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ldr r11, [r10, #TI_CPU] @ CPU number
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add r10, r10, #TI_VFPSTATE @ r10 = workspace
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ldr pc, [r4] @ call VFP entry point
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@ -370,3 +370,7 @@ struct op {
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u32 (* const fn)(int dd, int dn, int dm, u32 fpscr);
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u32 flags;
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};
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#ifdef CONFIG_SMP
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extern void vfp_save_state(void *location, u32 fpexc);
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#endif
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@ -65,6 +65,7 @@
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@ r2 = faulted PC+4
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@ r9 = successful return
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@ r10 = vfp_state union
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@ r11 = CPU number
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@ lr = failure return
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.globl vfp_support_entry
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@ -79,7 +80,7 @@ vfp_support_entry:
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DBGSTR1 "enable %x", r10
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ldr r3, last_VFP_context_address
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orr r1, r1, #FPEXC_ENABLE @ user FPEXC has the enable bit set
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ldr r4, [r3] @ last_VFP_context pointer
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ldr r4, [r3, r11, lsl #2] @ last_VFP_context pointer
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bic r5, r1, #FPEXC_EXCEPTION @ make sure exceptions are disabled
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cmp r4, r10
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beq check_for_exception @ we are returning to the same
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@ -91,7 +92,9 @@ vfp_support_entry:
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@ exceptions, so we can get at the
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@ rest of it
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#ifndef CONFIG_SMP
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@ Save out the current registers to the old thread state
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@ No need for SMP since this is not done lazily
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DBGSTR1 "save old state %p", r4
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cmp r4, #0
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@ -105,10 +108,11 @@ vfp_support_entry:
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stmia r4, {r1, r5, r6, r8} @ save FPEXC, FPSCR, FPINST, FPINST2
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@ and point r4 at the word at the
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@ start of the register dump
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#endif
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no_old_VFP_process:
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DBGSTR1 "load state %p", r10
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str r10, [r3] @ update the last_VFP_context pointer
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str r10, [r3, r11, lsl #2] @ update the last_VFP_context pointer
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@ Load the saved state back into the VFP
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VFPFLDMIA r10 @ reload the working registers while
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@ FPEXC is in a safe state
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@ -162,6 +166,24 @@ process_exception:
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@ required. If not, the user code will
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@ retry the faulted instruction
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#ifdef CONFIG_SMP
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.globl vfp_save_state
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.type vfp_save_state, %function
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vfp_save_state:
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@ Save the current VFP state
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@ r0 - save location
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@ r1 - FPEXC
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DBGSTR1 "save VFP state %p", r0
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VFPFMRX r2, FPSCR @ current status
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VFPFMRX r3, FPINST @ FPINST (always there, rev0 onwards)
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tst r1, #FPEXC_FPV2 @ is there an FPINST2 to read?
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VFPFMRX r12, FPINST2, NE @ FPINST2 if needed - avoids reading
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@ nonexistant reg on rev0
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VFPFSTMIA r0 @ save the working registers
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stmia r0, {r1, r2, r3, r12} @ save FPEXC, FPSCR, FPINST, FPINST2
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mov pc, lr
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#endif
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last_VFP_context_address:
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.word last_VFP_context
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@ -28,7 +28,7 @@ void vfp_testing_entry(void);
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void vfp_support_entry(void);
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void (*vfp_vector)(void) = vfp_testing_entry;
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union vfp_state *last_VFP_context;
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union vfp_state *last_VFP_context[NR_CPUS];
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/*
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* Dual-use variable.
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@ -41,13 +41,35 @@ static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v)
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{
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struct thread_info *thread = v;
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union vfp_state *vfp;
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__u32 cpu = thread->cpu;
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if (likely(cmd == THREAD_NOTIFY_SWITCH)) {
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u32 fpexc = fmrx(FPEXC);
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#ifdef CONFIG_SMP
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/*
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* On SMP, if VFP is enabled, save the old state in
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* case the thread migrates to a different CPU. The
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* restoring is done lazily.
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*/
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if ((fpexc & FPEXC_ENABLE) && last_VFP_context[cpu]) {
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vfp_save_state(last_VFP_context[cpu], fpexc);
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last_VFP_context[cpu]->hard.cpu = cpu;
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}
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/*
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* Thread migration, just force the reloading of the
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* state on the new CPU in case the VFP registers
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* contain stale data.
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*/
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if (thread->vfpstate.hard.cpu != cpu)
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last_VFP_context[cpu] = NULL;
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#endif
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/*
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* Always disable VFP so we can lazily save/restore the
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* old state.
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*/
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fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_ENABLE);
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fmxr(FPEXC, fpexc & ~FPEXC_ENABLE);
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return NOTIFY_DONE;
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}
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@ -68,8 +90,8 @@ static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v)
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}
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/* flush and release case: Per-thread VFP cleanup. */
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if (last_VFP_context == vfp)
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last_VFP_context = NULL;
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if (last_VFP_context[cpu] == vfp)
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last_VFP_context[cpu] = NULL;
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return NOTIFY_DONE;
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}
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@ -35,6 +35,9 @@ struct vfp_hard_struct {
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*/
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__u32 fpinst;
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__u32 fpinst2;
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#ifdef CONFIG_SMP
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__u32 cpu;
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#endif
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};
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union vfp_state {
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