[Xen-devel] [v8][PATCH 07/16] hvmloader/e820: construct guest e820 table

[Tiejun Chen <tiejun.chen@xxxxxxxxx>]

Now use the hypervisor-supplied memory map to build our final e820 table:
* Add regions for BIOS ranges and other special mappings not in the
  hypervisor map
* Add in the hypervisor regions
* Adjust the lowmem and highmem regions if we've had to relocate
  memory (adding a highmem region if necessary)
* Sort all the ranges so that they appear in memory order.

CC: Keir Fraser <keir@xxxxxxx>
CC: Jan Beulich <jbeulich@xxxxxxxx>
CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
CC: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
CC: Ian Campbell <ian.campbell@xxxxxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
Signed-off-by: Tiejun Chen <tiejun.chen@xxxxxxxxx>
---
v8:

* define low_mem_end as uint32_t

* Correct those two wrong loops, memory_map.nr_map -> nr
  when we're trying to revise low/high memory e820 entries.

* Improve code comments and the patch head description

* Add one check if highmem is just populated by hvmloader itself

v5 ~ v7:

* Nothing is changed.

v4:

* Rename local variable, low_mem_pgend, to low_mem_end.

* Improve some code comments

* Adjust highmem after lowmem is changed.
 
 
 tools/firmware/hvmloader/e820.c | 92 +++++++++++++++++++++++++++++++++++++----
 1 file changed, 83 insertions(+), 9 deletions(-)

diff --git a/tools/firmware/hvmloader/e820.c b/tools/firmware/hvmloader/e820.c
index b72baa5..aa678a7 100644
--- a/tools/firmware/hvmloader/e820.c
+++ b/tools/firmware/hvmloader/e820.c
@@ -108,7 +108,9 @@ int build_e820_table(struct e820entry *e820,
                      unsigned int lowmem_reserved_base,
                      unsigned int bios_image_base)
 {
-    unsigned int nr = 0;
+    unsigned int nr = 0, i, j;
+    uint64_t add_high_mem = 0;
+    uint32_t low_mem_end = hvm_info->low_mem_pgend << PAGE_SHIFT;
 
     if ( !lowmem_reserved_base )
             lowmem_reserved_base = 0xA0000;
@@ -152,13 +154,6 @@ int build_e820_table(struct e820entry *e820,
     e820[nr].type = E820_RESERVED;
     nr++;
 
-    /* Low RAM goes here. Reserve space for special pages. */
-    BUG_ON((hvm_info->low_mem_pgend << PAGE_SHIFT) < (2u << 20));
-    e820[nr].addr = 0x100000;
-    e820[nr].size = (hvm_info->low_mem_pgend << PAGE_SHIFT) - e820[nr].addr;
-    e820[nr].type = E820_RAM;
-    nr++;
-
     /*
      * Explicitly reserve space for special pages.
      * This space starts at RESERVED_MEMBASE an extends to cover various
@@ -194,9 +189,73 @@ int build_e820_table(struct e820entry *e820,
         nr++;
     }
 
+    /*
+     * Construct E820 table according to recorded memory map.
+     *
+     * The memory map created by toolstack may include,
+     *
+     * #1. Low memory region
+     *
+     * Low RAM starts at least from 1M to make sure all standard regions
+     * of the PC memory map, like BIOS, VGA memory-mapped I/O and vgabios,
+     * have enough space.
+     *
+     * #2. Reserved regions if they exist
+     *
+     * #3. High memory region if it exists
+     */
+    for ( i = 0; i < memory_map.nr_map; i++ )
+    {
+        e820[nr] = memory_map.map[i];
+        nr++;
+    }
+
+    /* Low RAM goes here. Reserve space for special pages. */
+    BUG_ON(low_mem_end < (2u << 20));
 
-    if ( hvm_info->high_mem_pgend )
+    /*
+     * Its possible to relocate RAM to allocate sufficient MMIO previously
+     * so low_mem_pgend would be changed over there. And here memory_map[]
+     * records the original low/high memory, so if low_mem_end is less than
+     * the original we need to revise low/high memory range in e820.
+     */
+    for ( i = 0; i < nr; i++ )
     {
+        uint64_t end = e820[i].addr + e820[i].size;
+        if ( e820[i].type == E820_RAM &&
+             low_mem_end > e820[i].addr && low_mem_end < end )
+        {
+            add_high_mem = end - low_mem_end;
+            e820[i].size = low_mem_end - e820[i].addr;
+        }
+    }
+
+    /*
+     * And then we also need to adjust highmem.
+     */
+    if ( add_high_mem )
+    {
+        for ( i = 0; i < nr; i++ )
+        {
+            if ( e820[i].type == E820_RAM &&
+                 e820[i].addr == (1ull << 32))
+            {
+                e820[i].size += add_high_mem;
+                add_high_mem = 0;
+                break;
+            }
+        }
+    }
+
+    /* Or this is just populated by hvmloader itself. */
+    if ( add_high_mem )
+    {
+        /*
+         * hvmloader should always update hvm_info->high_mem_pgend
+         * when it relocates RAM anywhere.
+         */
+        BUG_ON( !hvm_info->high_mem_pgend );
+
         e820[nr].addr = ((uint64_t)1 << 32);
         e820[nr].size =
             ((uint64_t)hvm_info->high_mem_pgend << PAGE_SHIFT) - e820[nr].addr;
@@ -204,6 +263,21 @@ int build_e820_table(struct e820entry *e820,
         nr++;
     }
 
+    /* Finally we need to sort all e820 entries. */
+    for ( j = 0; j < nr-1; j++ )
+    {
+        for ( i = j+1; i < nr; i++ )
+        {
+            if ( e820[j].addr > e820[i].addr )
+            {
+                struct e820entry tmp;
+                tmp = e820[j];
+                e820[j] = e820[i];
+                e820[i] = tmp;
+            }
+        }
+    }
+
     return nr;
 }
 
-- 
1.9.1


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