[v3,03/10] mini-os: don't assume contiguous RAM when initializing in PVH mode

Commit Message

Juergen Gross Dec. 21, 2021, 8:46 a.m. UTC

Sizing the available memory should respect memory holes, so look at
the memory map when setting the boundary for the memory allocator.

Signed-off-by: Juergen Gross <[e-mail]>
Reviewed-by: Samuel Thibault <[e-mail]>
---
V2:
- rename "max" to "start" (Samuel Thibault)
---
 arch/x86/mm.c  |  6 +-----
 e820.c         | 14 ++++++++------
 include/e820.h |  2 +-
 3 files changed, 10 insertions(+), 12 deletions(-)

Patch

diff --git a/arch/x86/mm.c b/arch/x86/mm.c
index 8df93da..3bf6170 100644
--- a/arch/x86/mm.c
+++ b/arch/x86/mm.c
@@ -107,7 +107,6 @@  void arch_mm_preinit(void *p)
 {
     long ret;
     domid_t domid = DOMID_SELF;
-    unsigned long max;
 
     pt_base = page_table_base;
     first_free_pfn = PFN_UP(to_phys(&_end));
@@ -117,11 +116,8 @@  void arch_mm_preinit(void *p)
         xprintk("could not get memory size\n");
         do_exit();
     }
-    last_free_pfn = ret;
 
-    max = e820_get_maxpfn();
-    if ( max < last_free_pfn )
-        last_free_pfn = max;
+    last_free_pfn = e820_get_maxpfn(ret);
 }
 #endif
 
diff --git a/e820.c b/e820.c
index 70286cb..8030f43 100644
--- a/e820.c
+++ b/e820.c
@@ -285,10 +285,10 @@  void arch_print_memmap(void)
 }
 #endif
 
-unsigned long e820_get_maxpfn(void)
+unsigned long e820_get_maxpfn(unsigned long pages)
 {
     int i;
-    unsigned long pfn, max = 0;
+    unsigned long pfns, start = 0;
 
     e820_get_memmap();
 
@@ -296,10 +296,12 @@  unsigned long e820_get_maxpfn(void)
     {
         if ( e820_map[i].type != E820_RAM )
             continue;
-        pfn = (e820_map[i].addr + e820_map[i].size) >> PAGE_SHIFT;
-        if ( pfn > max )
-            max = pfn;
+        pfns = e820_map[i].size >> PAGE_SHIFT;
+        start = e820_map[i].addr >> PAGE_SHIFT;
+        if ( pages <= pfns )
+            return start + pages;
+        pages -= pfns;
     }
 
-    return max;
+    return start + pfns;
 }
diff --git a/include/e820.h b/include/e820.h
index af2129f..6a57f05 100644
--- a/include/e820.h
+++ b/include/e820.h
@@ -49,6 +49,6 @@  struct __packed e820entry {
 extern struct e820entry e820_map[];
 extern unsigned e820_entries;
 
-unsigned long e820_get_maxpfn(void);
+unsigned long e820_get_maxpfn(unsigned long pages);
 
 #endif /*__E820_HEADER*/