svn commit: r368293 - head/sys/kern

[Oleksandr Tymoshenko]

Author: gonzo
Date: Thu Dec  3 05:39:27 2020
New Revision: 368293
URL: https://svnweb.freebsd.org/changeset/base/368293

Log:
  Add support for hw.physmem tunable for ARM/ARM64/RISC-V platforms
  
  hw.physmem tunable allows to limit number of physical memory available to the
  system. It's handled in machdep files for x86 and PowerPC. This patch adds
  required logic to the consolidated physmem management interface that is used by
  ARM, ARM64, and RISC-V.
  
  Submitted by:	Klara, Inc.
  Reviewed by:	mhorne
  Sponsored by:	Ampere Computing
  Differential Revision:	https://reviews.freebsd.org/D27152

Modified:
  head/sys/kern/subr_physmem.c

Modified: head/sys/kern/subr_physmem.c
==============================================================================
--- head/sys/kern/subr_physmem.c	Thu Dec  3 02:22:05 2020	(r368292)
+++ head/sys/kern/subr_physmem.c	Thu Dec  3 05:39:27 2020	(r368293)
@@ -38,6 +38,7 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/kernel.h>
 #include <sys/physmem.h>
 #include <vm/vm.h>
 #include <vm/vm_param.h>
@@ -141,6 +142,10 @@ physmem_print_tables(void)
 /*
  * Walk the list of hardware regions, processing it against the list of
  * exclusions that contain the given exflags, and generating an "avail list".
+ * 
+ * If maxphyssz is not zero it sets upper limit, in bytes, for the total
+ * "avail list" size. Walk stops once the limit is reached and the last region
+ * is cut short if necessary.
  *
  * Updates the value at *pavail with the sum of all pages in all hw regions.
  *
@@ -148,15 +153,17 @@ physmem_print_tables(void)
  */
 static size_t
 regions_to_avail(vm_paddr_t *avail, uint32_t exflags, size_t maxavail,
-    long *pavail, long *prealmem)
+    uint64_t maxphyssz, long *pavail, long *prealmem)
 {
 	size_t acnt, exi, hwi;
 	uint64_t end, start, xend, xstart;
 	long availmem, totalmem;
 	const struct region *exp, *hwp;
+	uint64_t availsz;
 
 	totalmem = 0;
 	availmem = 0;
+	availsz = 0;
 	acnt = 0;
 	for (hwi = 0, hwp = hwregions; hwi < hwcnt; ++hwi, ++hwp) {
 		start = hwp->addr;
@@ -202,6 +209,13 @@ regions_to_avail(vm_paddr_t *avail, uint32_t exflags, 
 			 * could affect the remainder of this hw region.
 			 */
 			if ((xstart > start) && (xend < end)) {
+
+				if ((maxphyssz != 0) &&
+				    (availsz + xstart - start > maxphyssz)) {
+					xstart = maxphyssz + start - availsz;
+				}
+				if (xstart <= start)
+					continue;
 				if (acnt > 0 &&
 				    avail[acnt - 1] == (vm_paddr_t)start) {
 					avail[acnt - 1] = (vm_paddr_t)xstart;
@@ -209,6 +223,7 @@ regions_to_avail(vm_paddr_t *avail, uint32_t exflags, 
 					avail[acnt++] = (vm_paddr_t)start;
 					avail[acnt++] = (vm_paddr_t)xstart;
 				}
+				availsz += (xstart - start);
 				availmem += atop((vm_offset_t)(xstart - start));
 				start = xend;
 				continue;
@@ -228,12 +243,20 @@ regions_to_avail(vm_paddr_t *avail, uint32_t exflags, 
 		 * available entry for it.
 		 */
 		if (end > start) {
+			if ((maxphyssz != 0) &&
+			    (availsz + end - start > maxphyssz)) {
+				end = maxphyssz + start - availsz;
+			}
+			if (end <= start)
+				break;
+
 			if (acnt > 0 && avail[acnt - 1] == (vm_paddr_t)start) {
 				avail[acnt - 1] = (vm_paddr_t)end;
 			} else {
 				avail[acnt++] = (vm_paddr_t)start;
 				avail[acnt++] = (vm_paddr_t)end;
 			}
+			availsz += end - start;
 			availmem += atop((vm_offset_t)(end - start));
 		}
 		if (acnt >= maxavail)
@@ -362,7 +385,7 @@ size_t
 physmem_avail(vm_paddr_t *avail, size_t maxavail)
 {
 
-	return (regions_to_avail(avail, EXFLAG_NOALLOC, maxavail, NULL, NULL));
+	return (regions_to_avail(avail, EXFLAG_NOALLOC, maxavail, 0, NULL, NULL));
 }
 
 /*
@@ -378,11 +401,15 @@ void
 physmem_init_kernel_globals(void)
 {
 	size_t nextidx;
+	u_long hwphyssz;
 
-	regions_to_avail(dump_avail, EXFLAG_NODUMP, PHYS_AVAIL_ENTRIES, NULL,
-	    NULL);
+	hwphyssz = 0;
+	TUNABLE_ULONG_FETCH("hw.physmem", &hwphyssz);
+
+	regions_to_avail(dump_avail, EXFLAG_NODUMP, PHYS_AVAIL_ENTRIES,
+	    hwphyssz, NULL, NULL);
 	nextidx = regions_to_avail(phys_avail, EXFLAG_NOALLOC,
-	    PHYS_AVAIL_ENTRIES, &physmem, &realmem);
+	    PHYS_AVAIL_ENTRIES, hwphyssz, &physmem, &realmem);
 	if (nextidx == 0)
 		panic("No memory entries in phys_avail");
 	Maxmem = atop(phys_avail[nextidx - 1]);