Lightly overhaul the memory sizing code again.

 - The kernel environment variable 'hw.physmem' can be used to set the
   amount of physical memory space, based at 0, that FreeBSD will use.
   Any memory detected over this limit is ignored.  Documentation for
   this is available under 'help set tunables' in the loader.

 - In the case where system memory size can't be accurately determined,
   hw.physmem is used as a best-guess memory size, but speculative
   probing will be used to determine actual memory size if any of the
   guesses or hints are 16M or more.

 - If RB_VERBOSE, we list the memory regions as we test them.

 - The compile-time option MAXMEM supplies a default value for
   'hw.physmem'.

1 files changed, 127 insertions, 80 deletions

diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index 5e563de..9c9cacd 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -35,7 +35,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)machdep.c	7.4 (Berkeley) 6/3/91
- *	$Id: machdep.c,v 1.347 1999/07/01 18:33:22 peter Exp $
+ *	$Id: machdep.c,v 1.348 1999/07/02 04:33:05 peter Exp $
  */
 
 #include "apm.h"
@@ -1123,6 +1123,18 @@ sdtossd(sd, ssd)
 
 #define PHYSMAP_SIZE	(2 * 8)
 
+/*
+ * Populate the (physmap) array with base/length pairs describing the
+ * available physical memory in the system, then test this memory and
+ * build the phys_avail array describing the actually-available memory.
+ *
+ * Total memory size may be constrained by the kernel environment variable
+ * hw.physmem or the compile-time define MAXMEM.
+ *
+ * If we cannot accurately determine the physical memory map, and the
+ * value from the RTC seems dubious, trust the value of hw.physmem/MAXMEM
+ * instead, but require a speculative probe of memory.
+ */
 static void
 getmemsize(int first)
 {
@@ -1133,16 +1145,60 @@ getmemsize(int first)
 	struct vm86context vmc;
 	vm_offset_t pa, physmap[PHYSMAP_SIZE];
 	pt_entry_t pte;
+	u_int64_t AllowMem, MaxMem, sanity;
+	const char *cp, *ep;
 	struct {
 		u_int64_t base;
 		u_int64_t length;
 		u_int32_t type;
 	} *smap;
-	int msize;
 
 	bzero(&vmf, sizeof(struct vm86frame));
 	bzero(physmap, sizeof(physmap));
 
+	/*
+	 * hw.maxmem is a size in bytes; we also allow k, m, and g suffixes
+	 * for the appropriate modifiers.
+	 * After this calculation, AllowMem is either 0 (no memory size cap) 
+	 * or the maximum memory size desired in bytes.
+	 */
+	AllowMem = 0;
+	if ((cp = getenv("hw.physmem")) != NULL) {
+		sanity = AllowMem = strtouq(cp, &ep, 0);
+		if ((ep != cp) && (*ep != 0)) {
+			switch(*ep) {
+			case 'g':
+			case 'G':
+				AllowMem <<= 10;
+			case 'm':
+			case 'M':
+				AllowMem <<= 10;
+			case 'k':
+			case 'K':
+				AllowMem <<= 10;
+				break;
+			default:
+				AllowMem = sanity = 0;
+			}
+			if (AllowMem < sanity)
+				AllowMem = 0;
+		}
+		if (AllowMem == 0)
+			printf("Warning: invalid memory limit '%s' specified\n", cp);
+	}
+#ifdef MAXMEM
+	if (AllowMem == 0)
+		AllowMem = MAXMEM * (u_int64_t)1024;
+#endif
+	if ((AllowMem != 0) && (boothowto & RB_VERBOSE))
+		printf("Physical memory use limited to %uk\n", (u_int)(AllowMem / 1024));
+	MaxMem = AllowMem;
+	if (AllowMem == 0)
+		AllowMem = (u_int64_t)1 << 32;	/* 4GB limit imposed by 32-bit pmap */
+
+	/*
+	 * Perform "base memory" related probes & setup
+	 */
 	vm86_intcall(0x12, &vmf);
 	basemem = vmf.vmf_ax;
 	if (basemem > 640) {
@@ -1152,7 +1208,7 @@ getmemsize(int first)
 	}
 
 	/*
-	 * XXX if biosbasemem is now < 640, there is `hole'
+	 * XXX if biosbasemem is now < 640, there is a `hole'
 	 * between the end of base memory and the start of
 	 * ISA memory.  The hole may be empty or it may
 	 * contain BIOS code or data.  Map it read/write so
@@ -1225,11 +1281,18 @@ getmemsize(int first)
 		if (smap->length == 0)
 			goto next_run;
 
-		if (smap->base > 0xffffffff) {
-			printf("%dK of memory above 4GB ignored\n",
-			    (u_int32_t)(smap->length / 1024));
+		if (smap->base >= AllowMem) {
+			printf("%uk of memory above %uk ignored\n",
+			    (u_int)(smap->length / 1024), (u_int)(AllowMem / 1024));
 			goto next_run;
 		}
+		if ((smap->base + smap->length) >= AllowMem) {
+			printf("%uk region truncated to %uk to fit %uk limit\n", 
+			       (u_int)(smap->length / 1024), 
+			       (u_int)((AllowMem - smap->base) / 1024),
+			       (u_int)(AllowMem / 1024));
+			smap->length = AllowMem - smap->base;
+		}
 
 		for (i = 0; i <= physmap_idx; i += 2) {
 			if (smap->base < physmap[i + 1]) {
@@ -1256,64 +1319,71 @@ getmemsize(int first)
 next_run:
 	} while (vmf.vmf_ebx != 0);
 
-	if (physmap[1] != 0)
-		goto physmap_done;
-
 	/*
-	 * try memory map with INT 15:E801
+	 * If we failed above, try memory map with INT 15:E801
 	 */
-	vmf.vmf_ax = 0xE801;
-	if (vm86_intcall(0x15, &vmf) == 0) {
-		extmem = vmf.vmf_cx + vmf.vmf_dx * 64;
-	} else {
+	if (physmap[1] == 0) {
+		vmf.vmf_ax = 0xE801;
+		if (vm86_intcall(0x15, &vmf) == 0) {
+			extmem = vmf.vmf_cx + vmf.vmf_dx * 64;
+		} else {
 #if 0
-		vmf.vmf_ah = 0x88;
-		vm86_intcall(0x15, &vmf);
-		extmem = vmf.vmf_ax;
+			vmf.vmf_ah = 0x88;
+			vm86_intcall(0x15, &vmf);
+			extmem = vmf.vmf_ax;
 #else
+			/*
+			 * Prefer the RTC value for extended memory, or
+			 * hw.physmem/MAXMEM overrides.
+			 */
+			if (MaxMem > (1024 * 1024)) {		/* < 1MB is insane */
+				extmem = (MaxMem / 1024) - 1024;
+			} else {
+				extmem = rtcin(RTC_EXTLO) + (rtcin(RTC_EXTHI) << 8);
+			}
+			/*
+			 * If the value from the RTC is >= 16M, there is a good
+			 * chance that it's lying.  Compaq systems never report
+			 * more than 16M, and no system can honestly report more
+			 * than 64M.  We should end up here only on extremely
+			 * old and broken systems.  In any case, qualify the value
+			 * that we've got here by actually checking for physical
+			 * memory later on.
+			 */
+			if (extmem >= 16 * 1024)
+				speculative_mprobe = TRUE;
+#endif
+		}
+
 		/*
-	 	 * Prefer the RTC value for extended memory.
+		 * Special hack for chipsets that still remap the 384k hole when
+		 * there's 16MB of memory - this really confuses people that
+		 * are trying to use bus mastering ISA controllers with the
+		 * "16MB limit"; they only have 16MB, but the remapping puts
+		 * them beyond the limit.
+		 *
+		 * If extended memory is between 15-16MB (16-17MB phys address range),
+		 *	chop it to 15MB.
 		 */
-		extmem = rtcin(RTC_EXTLO) + (rtcin(RTC_EXTHI) << 8);
-#endif
-	}
+		if ((extmem > 15 * 1024) && (extmem < 16 * 1024))
+			extmem = 15 * 1024;
 
-	/*
-	 * Only perform calculations in this section if there is no system
-	 * map; any system new enough that supports SMAP probably does not
-	 * need these workarounds.
-	 */
-	/*
-	 * Special hack for chipsets that still remap the 384k hole when
-	 *	there's 16MB of memory - this really confuses people that
-	 *	are trying to use bus mastering ISA controllers with the
-	 *	"16MB limit"; they only have 16MB, but the remapping puts
-	 *	them beyond the limit.
-	 */
-	/*
-	 * If extended memory is between 15-16MB (16-17MB phys address range),
-	 *	chop it to 15MB.
-	 */
-	if ((extmem > 15 * 1024) && (extmem < 16 * 1024))
-		extmem = 15 * 1024;
+		physmap[0] = 0;
+		physmap[1] = basemem * 1024;
+		physmap_idx = 2;
+		physmap[physmap_idx] = 0x100000;
+		physmap[physmap_idx + 1] = physmap[physmap_idx] + extmem * 1024;
 
-	physmap[0] = 0;
-	physmap[1] = basemem * 1024;
-	physmap_idx = 2;
-	physmap[physmap_idx] = 0x100000;
-	physmap[physmap_idx + 1] = physmap[physmap_idx] + extmem * 1024;
+	}
 
 	/*
-	 * Indicate that we wish to do a speculative search for memory
-	 * beyond the end of the reported size if the indicated amount
-	 * is 64M (or more).
-	 *
-	 * XXX we should only do this in the RTC / 0x88 case
+	 * Maxmem isn't the "maximum memory", it's one larger than the
+	 * highest page of the physical address space.  It should be
+	 * called something like "Maxphyspage".  We fiddle it again
+	 * later based on the results of the memory test.
 	 */
-	if (extmem >= 16 * 1024)
-		speculative_mprobe = TRUE;
-
-physmap_done:
+	Maxmem = physmap[physmap_idx + 1] / PAGE_SIZE;
+	
 	/*
 	 * Now, physmap contains a map of physical memory.
 	 */
@@ -1321,34 +1391,7 @@ physmap_done:
 #ifdef SMP
 	/* make hole for AP bootstrap code */
 	physmap[1] = mp_bootaddress(physmap[1] / 1024);
-#endif
 
-	/*
-	 * Maxmem isn't the "maximum memory", it's one larger than the
-	 * highest page of the physical address space.  It should be
-	 * called something like "Maxphyspage".
-	 */
-	Maxmem = physmap[physmap_idx + 1] / PAGE_SIZE;
-
-        /*
-         * If a specific amount of memory is indicated via the MAXMEM
-	 * option or the npx0 "msize", then don't do the speculative
-         * memory probe.
-         */
-#ifdef MAXMEM
-	Maxmem = MAXMEM / 4;
-	speculative_mprobe = FALSE;
-#endif
-
-	/* Allow final override from the kernel environment */
-	if (getenv_int("hw.physmem", &msize)) {
-		if (msize != 0) {
-			Maxmem = msize / 4;
-			speculative_mprobe = FALSE;
-		}
-	}
-
-#ifdef SMP
 	/* look for the MP hardware - needed for apic addresses */
 	mp_probe();
 #endif
@@ -1375,6 +1418,10 @@ physmap_done:
 	for (i = 0; i <= physmap_idx; i += 2) {
 		vm_offset_t end;
 
+		if (boothowto & RB_VERBOSE)
+			printf("Testing memory %uk to %uk\n",
+			       (u_int)(physmap[i] / 1024), 
+			       (u_int)((physmap[i] + physmap[i+1]) / 1024));
 		end = ptoa(Maxmem);
 		if (physmap[i + 1] < end)
 			end = trunc_page(physmap[i + 1]);