From e754e3fae198480789fe6d949087e6580f4f614b Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Tue, 21 Dec 2021 09:46:29 +0100
Subject: [PATCH] mini-os: don't assume contiguous RAM when initializing in PVH
 mode

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 <jgross@suse.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
---
 arch/x86/mm.c  |  6 +-----
 e820.c         | 14 ++++++++------
 include/e820.h |  2 +-
 3 files changed, 10 insertions(+), 12 deletions(-)

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..4c726d1 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 = 0, 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*/
-- 
2.39.5