vm: clear map cache after kernel requests

. fixes a dirty tlb situation (i.e. random crashes)
	  on some hardware, seemingly new intel architectures
	  (e.g. my desktop i7 machine)

kernel/arch/i386/memory.c

@@ -31,7 +31,7 @@ PUBLIC int i386_paging_enabled = 0;
 
 PRIVATE int psok = 0;
 
-#define FREE_PDES_PER_CPU	3
+#define FREE_PDES_PER_CPU	2
 #define MAX_FREEPDES		(FREE_PDES_PER_CPU * CONFIG_MAX_CPUS)
 PRIVATE int nfreepdes = 0, freepdes[MAX_FREEPDES];
 
@@ -145,7 +145,7 @@ PRIVATE int lin_lin_copy(const struct proc *srcproc, vir_bytes srclinaddr,
 	proc_nr_t procslot;
 
 	assert(vm_running);
-	assert(nfreepdes >= 3);
+	assert(nfreepdes >= 2);
 
 	assert(get_cpulocal_var(ptproc));
 	assert(get_cpulocal_var(proc_ptr));
@@ -645,7 +645,7 @@ int vm_phys_memset(phys_bytes ph, const u8_t c, phys_bytes bytes)
 		return OK;
 	}
 
-	assert(nfreepdes >= 3);
+	assert(nfreepdes >= 2);
 
 	assert(get_cpulocal_var(ptproc)->p_seg.p_cr3_v);
 

servers/vm/arch/i386/pagetable.c

@@ -36,6 +36,10 @@
 
 #include "memory.h"
 
+/* Free PDE slots we tell kernel about */
+#define FREE_PDES	2
+PRIVATE int first_free_pde = -1;
+
 /* PDE used to map in kernel, kernel physical address. */
 PRIVATE int id_map_high_pde = -1, pagedir_pde = -1;
 PRIVATE u32_t global_bit = 0, pagedir_pde_val;
@@ -638,6 +642,18 @@ PUBLIC int pt_ptmap(struct vmproc *src_vmp, struct vmproc *dst_vmp)
 	return OK;
 }
 
+PUBLIC int pt_clearmapcache(void)
+{
+	int f;
+	/* Make sure kernel will invalidate tlb when using current
+	 * pagetable (i.e. vm's) to make new mappings before new cr3
+	 * is loaded.
+	 */
+	for(f = first_free_pde; f < first_free_pde+FREE_PDES; f++) {
+		vmprocess->vm_pt.pt_dir[f] = 0;
+	}
+}
+
 /*===========================================================================*
  *				pt_writemap		     		     *
  *===========================================================================*/
@@ -876,6 +892,7 @@ PUBLIC void pt_init(phys_bytes usedlimit)
 	vir_bytes sparepages_mem;
 	phys_bytes sparepages_ph;
 	vir_bytes ptr;
+	int f = 0;
 
         /* Shorthand. */
         newpt = &vmprocess->vm_pt;
@@ -1030,10 +1047,12 @@ PUBLIC void pt_init(phys_bytes usedlimit)
 			I386_VM_PRESENT | I386_VM_USER | I386_VM_WRITE;
 
 	/* Tell kernel about free pde's. */
-	while(free_pde*I386_BIG_PAGE_SIZE < VM_PROCSTART) {
+	first_free_pde = free_pde;
+	while(free_pde*I386_BIG_PAGE_SIZE < VM_PROCSTART && f < FREE_PDES) {
 		if((r=sys_vmctl(SELF, VMCTL_I386_FREEPDE, free_pde++)) != OK) {
 			panic("VMCTL_I386_FREEPDE failed: %d", r);
 		}
+		f++;
 	}
 
 	/* first pde in use by process. */

servers/vm/main.c

@@ -112,6 +112,7 @@ PUBLIC int main(void)
 					"message!\n", msg.m_source);
 		}
 		do_pagefaults(&msg);
+		pt_clearmapcache();
 		/*
 		 * do not reply to this call, the caller is unblocked by
 		 * a sys_vmctl() call in do_pagefaults if success. VM panics
@@ -419,6 +420,8 @@ PRIVATE void sef_cb_signal_handler(int signo)
 	if(missing_spares > 0) {
 		pt_cycle();	/* pagetable code wants to be called */
 	}
+
+	pt_clearmapcache();
 }
 
 /*===========================================================================*