SMP - lazy FPU

- when a process is migrated to a different CPU it may have an active
  FPU context in the processor registers. We must save it and migrate
  it together with the process.

kernel/arch/i386/arch_smp.c

@@ -60,6 +60,7 @@ PRIVATE phys_bytes copy_trampoline(void)
 
 	tramp_size = (unsigned) &__trampoline_end - (unsigned)&trampoline;
 	s = env_get("memory");
+	s = (char *) get_value(params_buffer, "memory");
 	if (!s)
 		return 0;
 	
@@ -238,6 +239,7 @@ PRIVATE void ap_finish_booting(void)
 	printf("CPU %d paging is on\n", cpu);
 
 	lapic_enable(cpu);
+	fpu_init();
 
 	if (app_cpu_init_timer(system_hz)) {
 		panic("FATAL : failed to initialize timer interrupts CPU %d, "

kernel/arch/i386/arch_system.c

@@ -205,7 +205,7 @@ PUBLIC void arch_get_aout_headers(const int i, struct exec *h)
 	phys_copy(aout + i * A_MINHDR, vir2phys(h), (phys_bytes) A_MINHDR);
 }
 
-PRIVATE void fpu_init(void)
+PUBLIC void fpu_init(void)
 {
 	unsigned short cw, sw;
 
@@ -219,10 +219,8 @@ PRIVATE void fpu_init(void)
 		 * Set CR0_NE and CR0_MP to handle fpu exceptions
 		 * in native mode. */
 		write_cr0(read_cr0() | CR0_MP_NE);
-		fpu_presence = 1;
+		get_cpulocal_var(fpu_presence) = 1;
 		if(_cpufeature(_CPUF_I386_FXSR)) {
-			register struct proc *rp;
-			phys_bytes aligned_fp_area;
 			u32_t cr4 = read_cr4() | CR4_OSFXSR; /* Enable FXSR. */
 
 			/* OSXMMEXCPT if supported
@@ -233,35 +231,18 @@ PRIVATE void fpu_init(void)
 
 			write_cr4(cr4);
 			osfxsr_feature = 1;
-
-			for (rp = BEG_PROC_ADDR; rp < END_PROC_ADDR; ++rp) {
-				/* FXSR requires 16-byte alignment of memory
-				 * image, but unfortunately some old tools
-				 * (probably linker) ignores ".balign 16"
-				 * applied to our memory image.
-				 * Thus we have to do manual alignment.
-				 */
-				aligned_fp_area =
-					(phys_bytes) &rp->p_fpu_state.fpu_image;
-				if(aligned_fp_area % FPUALIGN) {
-				    aligned_fp_area += FPUALIGN -
-						   (aligned_fp_area % FPUALIGN);
-				}
-				rp->p_fpu_state.fpu_save_area_p =
-						    (void *) aligned_fp_area;
-			}
 		} else {
 			osfxsr_feature = 0;
 		}
 	} else {
 		/* No FPU presents. */
-                fpu_presence = 0;
+		get_cpulocal_var(fpu_presence) = 0;
                 osfxsr_feature = 0;
                 return;
         }
 }
 
-PUBLIC void save_fpu(struct proc *pr)
+PUBLIC void save_local_fpu(struct proc *pr)
 {
 	if(!fpu_presence)
 		return;
@@ -275,6 +256,34 @@ PUBLIC void save_fpu(struct proc *pr)
 	}
 }
 
+PUBLIC void save_fpu(struct proc *pr)
+{
+#if CONFIG_SMP
+	if (cpuid == pr->p_cpu) {
+		save_local_fpu(pr);
+	}
+	else {
+		int stopped;
+
+		/* remember if the process was already stopped */
+		stopped = RTS_ISSET(pr, RTS_PROC_STOP);
+
+		/* stop the remote process and force it's context to be saved */
+		smp_schedule_stop_proc_save_ctx(pr);
+
+		/*
+		 * If the process wasn't stopped let the process run again. The
+		 * process is kept block by the fact that the kernel cannot run
+		 * on its cpu
+		 */
+		if (!stopped)
+			RTS_UNSET(pr, RTS_PROC_STOP);
+	}
+#else
+	save_local_fpu(pr);
+#endif
+}
+
 PUBLIC void restore_fpu(struct proc *pr)
 {
 	if(!proc_used_fpu(pr)) {
@@ -328,8 +337,6 @@ PUBLIC void arch_init(void)
 		BOOT_VERBOSE(printf("APIC not present, using legacy PIC\n"));
 	}
 #endif
-
-	fpu_init();
 }
 
 PUBLIC void ser_putc(char c)

kernel/cpulocals.h

@@ -78,6 +78,9 @@ DECLARE_CPULOCAL(int, cpu_is_idle); /* let the others know that you are idle */
 
 DECLARE_CPULOCAL(u64_t ,tsc_ctr_switch); /* when did we switched time accounting */
 
+DECLARE_CPULOCAL(char ,fpu_presence); /* whether the cpu has FPU or not */
+DECLARE_CPULOCAL(struct proc * ,fpu_owner); /* who owns the FPU of the local cpu */
+
 DECLARE_CPULOCAL_END
 
 #endif /* __ASSEMBLY__ */

kernel/glo.h

@@ -44,7 +44,6 @@ EXTERN time_t boottime;
 EXTERN char params_buffer[512];		/* boot monitor parameters */
 EXTERN int minix_panicing;
 EXTERN char fpu_presence;
-EXTERN struct proc * fpu_owner;
 EXTERN int verboseboot;			/* verbose boot, init'ed in cstart */
 #define MAGICTEST 0xC0FFEE23
 EXTERN u32_t magictest;			/* global magic number */

kernel/main.c

@@ -32,7 +32,6 @@
 /* Prototype declarations for PRIVATE functions. */
 FORWARD _PROTOTYPE( void announce, (void));	
 
-void ser_dump_queues(void);
 PUBLIC void bsp_finish_booting(void)
 {
   int i;
@@ -69,6 +68,19 @@ PUBLIC void bsp_finish_booting(void)
 			  "cannot continue without any clock source!");
   }
 
+  fpu_init();
+
+#ifdef CONFIG_WATCHDOG
+  if (watchdog_enabled) {
+	  if (arch_watchdog_init()) {
+		  printf("WARNING watchdog initialization failed! Disabled\n");
+		  watchdog_enabled = 0;
+	  }
+	  else
+		  BOOT_VERBOSE(printf("Watchdog enabled\n"););
+  }
+#endif
+
 /* Warnings for sanity checks that take time. These warnings are printed
  * so it's a clear warning no full release should be done with them
  * enabled.

kernel/proc.c

@@ -155,6 +155,23 @@ PUBLIC void proc_init(void)
 		ip->p_rts_flags |= RTS_PROC_STOP;
 		set_idle_name(ip->p_name, i);
 	}
+
+	for (rp = BEG_PROC_ADDR; rp < END_PROC_ADDR; ++rp) {
+		/*
+		 * FXSR requires 16-byte alignment of memory image, but
+		 * unfortunately a.out does not preserve the alignment while
+		 * linking.  Thus we have to do manual alignment.
+		 */
+		phys_bytes aligned_fp_area;
+		aligned_fp_area =
+			(phys_bytes) &rp->p_fpu_state.fpu_image;
+		if(aligned_fp_area % FPUALIGN) {
+			aligned_fp_area += FPUALIGN -
+				(aligned_fp_area % FPUALIGN);
+		}
+		rp->p_fpu_state.fpu_save_area_p =
+			(void *) aligned_fp_area;
+	}
 }
 
 PRIVATE void switch_address_space_idle(void)
@@ -346,7 +363,7 @@ check_misc_flags:
 	context_stop(proc_addr(KERNEL));
 
 	/* If the process isn't the owner of FPU, enable the FPU exception */
-	if(fpu_owner != p)
+	if(get_cpulocal_var(fpu_owner) != p)
 		enable_fpu_exception();
 	else
 		disable_fpu_exception();
@@ -1573,6 +1590,7 @@ PUBLIC void proc_no_time(struct proc * p)
 PUBLIC void copr_not_available_handler(void)
 {
 	struct proc * p;
+	struct proc ** local_fpu_owner;
 	/*
 	 * Disable the FPU exception (both for the kernel and for the process
 	 * once it's scheduled), and initialize or restore the FPU state.
@@ -1583,9 +1601,10 @@ PUBLIC void copr_not_available_handler(void)
 	p = get_cpulocal_var(proc_ptr);
 
 	/* if FPU is not owned by anyone, do not store anything */
-	if (fpu_owner != NULL) {
-		assert(fpu_owner != p);
-		save_fpu(fpu_owner);
+	local_fpu_owner = get_cpulocal_var_ptr(fpu_owner);
+	if (*local_fpu_owner != NULL) {
+		assert(*local_fpu_owner != p);
+		save_local_fpu(*local_fpu_owner);
 	}
 
 	/*
@@ -1593,12 +1612,17 @@ PUBLIC void copr_not_available_handler(void)
 	 * schedule!
 	 */
 	restore_fpu(p);
-	fpu_owner = p;
+	*local_fpu_owner = p;
 	context_stop(proc_addr(KERNEL));
 	restore_user_context(p);
 	NOT_REACHABLE;
 }
 
-PUBLIC void release_fpu(void) {
-	fpu_owner = NULL;
+PUBLIC void release_fpu(struct proc * p) {
+	struct proc ** fpu_owner_ptr;
+
+	fpu_owner_ptr = get_cpu_var_ptr(p->p_cpu, fpu_owner);
+
+	if (*fpu_owner_ptr == p)
+		*fpu_owner_ptr = NULL;
 }

kernel/proto.h

@@ -34,6 +34,7 @@ _PROTOTYPE( void context_stop, (struct proc * p)			);
 _PROTOTYPE( void context_stop_idle, (void)				);
 _PROTOTYPE( void restore_fpu, (struct proc *)				);
 _PROTOTYPE( void save_fpu, (struct proc *)				);
+_PROTOTYPE( void save_local_fpu, (struct proc *)			);
 _PROTOTYPE( void fpu_sigcontext, (struct proc *, struct sigframe *fr, struct sigcontext *sc)	);
 
 /* main.c */
@@ -178,6 +179,10 @@ _PROTOTYPE( vir_bytes alloc_remote_segment, (u32_t *, segframe_t *,
 _PROTOTYPE( int intr_init, (int, int)					);
 _PROTOTYPE( void halt_cpu, (void)                                	);
 _PROTOTYPE( void arch_init, (void)                                     );
+/* arch dependent FPU initialization per CPU */
+_PROTOTYPE( void fpu_init, (void)					);
+/* returns true if pfu is present and initialized */
+_PROTOTYPE( int is_fpu, (void)						);
 _PROTOTYPE( void ser_putc, (char)						);
 _PROTOTYPE( __dead void arch_shutdown, (int)				);
 _PROTOTYPE( __dead void arch_monitor, (void)				);
@@ -213,7 +218,7 @@ _PROTOTYPE(void release_address_space, (struct proc *pr));
 
 _PROTOTYPE(void enable_fpu_exception, (void));
 _PROTOTYPE(void disable_fpu_exception, (void));
-_PROTOTYPE(void release_fpu, (void));
+_PROTOTYPE(void release_fpu, (struct proc * p));
 
 /* utility.c */
 _PROTOTYPE( void cpu_print_freq, (unsigned cpu));

kernel/smp.c

@@ -19,6 +19,7 @@ PRIVATE struct sched_ipi_data  sched_ipi_data[CONFIG_MAX_CPUS];
 
 #define SCHED_IPI_STOP_PROC	1
 #define SCHED_IPI_VM_INHIBIT	2
+#define SCHED_IPI_SAVE_CTX	4
 
 static volatile unsigned ap_cpus_booted;
 
@@ -116,6 +117,30 @@ PUBLIC void smp_schedule_vminhibit(struct proc * p)
 	assert(RTS_ISSET(p, RTS_VMINHIBIT));
 }
 
+PUBLIC void smp_schedule_stop_proc_save_ctx(struct proc * p)
+{
+	/*
+	 * stop the processes and force the complete context of the process to
+	 * be saved (i.e. including FPU state and such)
+	 */
+	smp_schedule_sync(p, SCHED_IPI_STOP_PROC | SCHED_IPI_SAVE_CTX);
+	assert(RTS_ISSET(p, RTS_PROC_STOP));
+}
+
+PUBLIC void smp_schedule_migrate_proc(struct proc * p, unsigned dest_cpu)
+{
+	/*
+	 * stop the processes and force the complete context of the process to
+	 * be saved (i.e. including FPU state and such)
+	 */
+	smp_schedule_sync(p, SCHED_IPI_STOP_PROC | SCHED_IPI_SAVE_CTX);
+	assert(RTS_ISSET(p, RTS_PROC_STOP));
+	
+	/* assign the new cpu and let the process run again */
+	p->p_cpu = dest_cpu;
+	RTS_UNSET(p, RTS_PROC_STOP);
+}
+
 PUBLIC void smp_ipi_sched_handler(void)
 {
 	struct proc * curr;
@@ -134,6 +159,16 @@ PUBLIC void smp_ipi_sched_handler(void)
 		if (flgs & SCHED_IPI_STOP_PROC) {
 			RTS_SET(p, RTS_PROC_STOP);
 		}
+		if (flgs & SCHED_IPI_SAVE_CTX) {
+			/* all context have been save already,  FPU remains */
+			if (proc_used_fpu(p) &&
+					get_cpulocal_var(fpu_owner) == p) {
+				disable_fpu_exception();
+				save_local_fpu(p);
+				/* we re preparing to migrate somewhere else */
+				release_fpu(p);
+			}
+		}
 		if (flgs & SCHED_IPI_VM_INHIBIT) {
 			RTS_SET(p, RTS_VMINHIBIT);
 		}

kernel/smp.h

@@ -63,6 +63,11 @@ _PROTOTYPE(void smp_schedule, (unsigned cpu));
 _PROTOTYPE(void smp_schedule_stop_proc, (struct proc * p));
 /* stop a process on a different cpu because its adress space is being changed */
 _PROTOTYPE(void smp_schedule_vminhibit, (struct proc * p));
+/* stop the process and for saving its full context */
+_PROTOTYPE(void smp_schedule_stop_proc_save_ctx, (struct proc * p));
+/* migrate the full context of a process to the destination CPU */
+_PROTOTYPE(void smp_schedule_migrate_proc,
+		(struct proc * p, unsigned dest_cpu));
 
 _PROTOTYPE(void arch_send_smp_schedule_ipi, (unsigned cpu));
 _PROTOTYPE(void arch_smp_halt_cpu, (void));

kernel/system.c

@@ -669,9 +669,7 @@ PUBLIC int sched_proc(struct proc *p,
 	if (proc_is_runnable(p)) {
 #ifdef CONFIG_SMP
 		if (p->p_cpu != cpuid && cpu != -1 && cpu != p->p_cpu) {
-			printf("WARNING : changing cpu of a runnable process %d "
-					"on a different cpu!\n", p->p_endpoint);
-			return(EINVAL);
+			smp_schedule_migrate_proc(p, cpu);
 		}
 #endif
 

kernel/system/do_clear.c

@@ -54,6 +54,9 @@ PUBLIC int do_clear(struct proc * caller, message * m_ptr)
    * and mark slot as FREE. Also mark saved fpu contents as not significant.
    */
   RTS_SETFLAGS(rc, RTS_SLOT_FREE);
+  
+  /* release FPU */
+  release_fpu(rc);
   rc->p_misc_flags &= ~MF_FPU_INITIALIZED;
 
   /* Release the process table slot. If this is a system process, also
@@ -70,10 +73,6 @@ PUBLIC int do_clear(struct proc * caller, message * m_ptr)
   }
 #endif
 
-  /* release FPU */
-  if (fpu_owner == rc)
-	  release_fpu();
-
   return OK;
 }
 

kernel/system/do_exec.c

@@ -46,8 +46,7 @@ PUBLIC int do_exec(struct proc * caller, message * m_ptr)
    * will be initialized, when it's used next time. */
   rp->p_misc_flags &= ~MF_FPU_INITIALIZED;
   /* force reloading FPU if the current process is the owner */
-  if (rp == fpu_owner)
-	  release_fpu();
+  release_fpu(rp);
   return(OK);
 }
 #endif /* USE_EXEC */

kernel/system/do_fork.c

@@ -53,10 +53,7 @@ PUBLIC int do_fork(struct proc * caller, message * m_ptr)
   map_ptr= (struct mem_map *) m_ptr->PR_MEM_PTR;
 
   /* make sure that the FPU context is saved in parent before copy */
-  if (fpu_owner == rpp) {
-	  disable_fpu_exception();
-	  save_fpu(rpp);
-  }
+  save_fpu(rpp);
   /* Copy parent 'proc' struct to child. And reinitialize some fields. */
   gen = _ENDPOINT_G(rpc->p_endpoint);
 #if (_MINIX_CHIP == _CHIP_INTEL)

kernel/system/do_mcontext.c

@@ -43,10 +43,7 @@ PUBLIC int do_getmcontext(struct proc * caller, message * m_ptr)
   mc.mc_fpu_flags = 0;
   if (proc_used_fpu(rp)) {
 	/* make sure that the FPU context is saved into proc structure first */
-	if (fpu_owner == rp) {
-		disable_fpu_exception();
-		save_fpu(rp);
-	}
+	save_fpu(rp);
 	mc.mc_fpu_flags = 0 | rp->p_misc_flags & MF_FPU_INITIALIZED;
 	memcpy(&(mc.mc_fpu_state), rp->p_fpu_state.fpu_save_area_p,
 							FPU_XFP_SIZE);
@@ -92,8 +89,7 @@ PUBLIC int do_setmcontext(struct proc * caller, message * m_ptr)
   } else
 	rp->p_misc_flags &= ~MF_FPU_INITIALIZED;
   /* force reloading FPU in either case */
-  if (fpu_owner == rp)
-	  release_fpu();
+  release_fpu(rp);
 #endif
 
   return(OK);

kernel/system/do_sigreturn.c

@@ -60,8 +60,7 @@ PUBLIC int do_sigreturn(struct proc * caller, message * m_ptr)
 		FPU_XFP_SIZE);
 	rp->p_misc_flags |=  MF_FPU_INITIALIZED; /* Restore math usage flag. */
 	/* force reloading FPU */
-	if (fpu_owner == rp)
-		release_fpu();
+	release_fpu(rp);
   }
 #endif
 

kernel/system/do_sigsend.c

@@ -46,10 +46,7 @@ PUBLIC int do_sigsend(struct proc * caller, message * m_ptr)
   #if (_MINIX_CHIP == _CHIP_INTEL)
     if(proc_used_fpu(rp)) {
 	    /* save the FPU context before saving it to the sig context */
-	    if (fpu_owner == rp) {
-		    disable_fpu_exception();
-		    save_fpu(rp);
-	    }
+	    save_fpu(rp);
 	    memcpy(&sc.sc_fpu_state, rp->p_fpu_state.fpu_save_area_p,
 	   	 FPU_XFP_SIZE);
     }

kernel/utility.c

@@ -80,3 +80,8 @@ PUBLIC void cpu_print_freq(unsigned cpu)
 	freq = cpu_get_freq(cpu);
 	printf("CPU %d freq %lu MHz\n", cpu, div64u(freq, 1000000));
 }
+
+PUBLIC int is_fpu(void)
+{
+	return get_cpulocal_var(fpu_presence);
+}