svn commit: r335783 - head/sys/mips/malta

[John Baldwin]

Author: jhb
Date: Thu Jun 28 21:27:34 2018
New Revision: 335783
URL: https://svnweb.freebsd.org/changeset/base/335783

Log:
  Support 2GB of memory on Malta systems with FreeBSD/mips.
  
  When 2GB of memory is enabled for QEMU's Malta emulation, the physical
  memory ends at an address of 2^32 - 1.  This causes an integer overflow
  to zero when computing the upper bound of the second phys_avail[] range.
  As a result, FreeBSD/mips kernels were only using the first 256MB of
  RAM and ignoring the remaining 1.75GB.  To work around this, truncate
  the extended memory size to 2GB minus one page for 32-bit mips kernels.
  
  Sponsored by:	DARPA / AFRL
  Differential Revision:	https://reviews.freebsd.org/D16027

Modified:
  head/sys/mips/malta/malta_machdep.c

Modified: head/sys/mips/malta/malta_machdep.c
==============================================================================
--- head/sys/mips/malta/malta_machdep.c	Thu Jun 28 21:26:14 2018	(r335782)
+++ head/sys/mips/malta/malta_machdep.c	Thu Jun 28 21:27:34 2018	(r335783)
@@ -344,6 +344,15 @@ platform_start(__register_t a0, __register_t a1,  __re
 		printf("memsize = %llu (0x%08x)\n",
 		    (unsigned long long) memsize, memsize);
 		printf("ememsize = %llu\n", (unsigned long long) ememsize);
+
+#ifdef __mips_o32
+		/*
+		 * For O32 phys_avail[] can't address memory beyond 2^32,
+		 * so cap extended memory to 2GB minus one page.
+		 */
+		if (ememsize >= 2ULL * 1024 * 1024 * 1024)
+			ememsize = 2ULL * 1024 * 1024 * 1024 - PAGE_SIZE;
+#endif
 	}
 
 	/*