Re: [Xen-devel] pv_grub and >1023M RAM == death

[Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>]

Hello,

Christopher S. Aker, le Wed 03 Dec 2008 14:05:55 -0500, a écrit :
> pv_grub x86, when booted with more than 1023MB of RAM, will produce the 
> following output:

Ah, mini-os doesn't have any protection against that.  I don't have a
machine here to test, could you check the patch below?

Samuel



Clip memory not usable by Mini-OS (above 1GB)

signed-off-by: samuel.thibault@xxxxxxxxxxxx

diff -r 4c67985c552e extras/mini-os/arch/x86/mm.c
--- a/extras/mini-os/arch/x86/mm.c      Wed Nov 19 13:17:31 2008 +0000
+++ b/extras/mini-os/arch/x86/mm.c      Fri Dec 05 00:19:19 2008 +0100
@@ -420,7 +420,9 @@
 #define DEMAND_MAP_PAGES ((2ULL << 30) / PAGE_SIZE)
 #endif
 
-#ifdef HAVE_LIBC
+#ifndef HAVE_LIBC
+#define HEAP_PAGES 0
+#else
 unsigned long heap, brk, heap_mapped, heap_end;
 #ifdef __x86_64__
 #define HEAP_PAGES ((128ULL << 30) / PAGE_SIZE)
@@ -591,7 +593,7 @@
 void arch_init_mm(unsigned long* start_pfn_p, unsigned long* max_pfn_p)
 {
 
-    unsigned long start_pfn, max_pfn;
+    unsigned long start_pfn, max_pfn, virt_pfns;
 
     printk("  _text:        %p\n", &_text);
     printk("  _etext:       %p\n", &_etext);
@@ -604,7 +606,12 @@
     start_pfn = PFN_UP(to_phys(start_info.pt_base)) + 
                 start_info.nr_pt_frames + 3;
     max_pfn = start_info.nr_pages;
-   
+
+    /* We need room for demand mapping and heap, clip available memory */
+    virt_pfns = DEMAND_MAP_PAGES + HEAP_PAGES;
+    if (max_pfn + virt_pfns + 1 < max_pfn)
+        max_pfn = -(virt_pfns + 1);
+
     printk("  start_pfn:    %lx\n", start_pfn);
     printk("  max_pfn:      %lx\n", max_pfn);
 

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