Changed pagefault delivery to VM

this patch changes the way pagefaults are delivered to VM. It adopts
the same model as the out-of-quantum messages sent by kernel to a
scheduler.

- everytime a userspace pagefault occurs, kernel creates a message
  which is sent to VM on behalf of the faulting process

- the process is blocked on delivery to VM in the standard IPC code
  instead of waiting in a spacial in-kernel queue (stack) and is not
  runnable until VM tell kernel that the pagefault is resolved and is
  free to clear the RTS_PAGEFAULT flag.

- VM does not need call kernel and poll the pagefault information
  which saves many (1/2?) calls and kernel calls that return "no more
  data"

- VM notification by kernel does not need to use signals

- each entry in proc table is by 12 bytes smaller (~3k save)

kernel/arch/i386/arch_do_vmctl.c

@@ -41,19 +41,6 @@ struct proc *p;
 		/* Increase process SP. */
 		p->p_reg.sp += m_ptr->SVMCTL_VALUE;
 		return OK;
-        case VMCTL_GET_PAGEFAULT:
-	{
-  		struct proc *rp;
-		if(!(rp=pagefaults))
-			return ESRCH;
-		pagefaults = rp->p_nextpagefault;
-		if(!RTS_ISSET(rp, RTS_PAGEFAULT))
-			panic( "non-PAGEFAULT process on pagefault chain: %d", 				rp->p_endpoint);
-                m_ptr->SVMCTL_PF_WHO = rp->p_endpoint;
-                m_ptr->SVMCTL_PF_I386_CR2 = rp->p_pagefault.pf_virtual;
-		m_ptr->SVMCTL_PF_I386_ERR = rp->p_pagefault.pf_flags;
-		return OK;
-	}
 	case VMCTL_I386_KERNELLIMIT:
 	{
 		int r;

kernel/arch/i386/exception.c

@@ -20,6 +20,8 @@ void pagefault( struct proc *pr,
 	int in_physcopy = 0;
 
 	reg_t pagefaultcr2;
+	message m_pagefault;
+	int err;
 
 	assert(frame);
 
@@ -77,17 +79,16 @@ void pagefault( struct proc *pr,
 	assert(!RTS_ISSET(pr, RTS_PAGEFAULT));
 	RTS_SET(pr, RTS_PAGEFAULT);
 
-	/* Save pagefault details, suspend process,
-	 * add process to pagefault chain,
-	 * and tell VM there is a pagefault to be
-	 * handled.
-	 */
-	pr->p_pagefault.pf_virtual = pagefaultcr2;
-	pr->p_pagefault.pf_flags = frame->errcode;
-	pr->p_nextpagefault = pagefaults;
-	pagefaults = pr;
-		
-	send_sig(VM_PROC_NR, SIGKPF);
+	/* tell Vm about the pagefault */
+	m_pagefault.m_source = pr->p_endpoint;
+	m_pagefault.m_type   = VM_PAGEFAULT;
+	m_pagefault.VPF_ADDR = pagefaultcr2;
+	m_pagefault.VPF_FLAGS = frame->errcode;
+
+	if ((err = mini_send(pr, VM_PROC_NR,
+					&m_pagefault, FROM_KERNEL))) {
+		panic("WARNING: pagefault: mini_send returned %d\n", err);
+	}
 
 	return;
 }

kernel/glo.h

@@ -28,7 +28,6 @@ EXTERN struct loadinfo kloadinfo;	/* status of load average */
 EXTERN struct proc *proc_ptr;	/* pointer to currently running process */
 EXTERN struct proc *bill_ptr;	/* process to bill for clock ticks */
 EXTERN struct proc *vmrequest;  /* first process on vmrequest queue */
-EXTERN struct proc *pagefaults; /* first process on pagefault queue */
 EXTERN unsigned lost_ticks;	/* clock ticks counted outside clock task */
 
 

kernel/proc.h

@@ -31,8 +31,6 @@ struct proc {
   struct proc *p_scheduler;	/* who should get out of quantum msg */
 
   struct mem_map p_memmap[NR_LOCAL_SEGS];   /* memory map (T, D, S) */
-  struct pagefault p_pagefault;	/* valid if PAGEFAULT in p_rts_flags set */
-  struct proc *p_nextpagefault;	/* next on PAGEFAULT chain */
 
   clock_t p_user_time;		/* user time in ticks */
   clock_t p_sys_time;		/* sys time in ticks */