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Re: [Xen-devel] [PATCH v2 4/4] xen-all: Pass max_ram_below_4g to xen_hvm_init.



On 03/17/14 13:55, Stefano Stabellini wrote:
On Mon, 17 Mar 2014, Don Slutz wrote:
On 03/16/14 12:10, Stefano Stabellini wrote:
On Tue, 11 Mar 2014, Don Slutz wrote:
This is the xen part of "pc & q35: Add new object pc-memory-layout."

Signed-off-by: Don Slutz<dslutz@xxxxxxxxxxx>
---
   hw/i386/pc_piix.c    |  4 ++--
   hw/i386/pc_q35.c     |  4 ++--
   include/hw/xen/xen.h |  4 ++--
   xen-all.c            | 41 ++++++++++++++++++++++-------------------
   xen-stub.c           |  4 ++--
   5 files changed, 30 insertions(+), 27 deletions(-)

diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index 964ea33..691fc5d 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -131,8 +131,8 @@ static void pc_init1(QEMUMachineInitArgs *args,
           below_4g_mem_size = args->ram_size;
       }
   -    if (xen_enabled() && xen_hvm_init(&below_4g_mem_size,
&above_4g_mem_size,
-                                      &ram_memory) != 0) {
+    if (xen_enabled() && xen_hvm_init(max_ram_below_4g,
&below_4g_mem_size,
+                                      &above_4g_mem_size, &ram_memory) !=
0) {
           fprintf(stderr, "xen hardware virtual machine initialisation
failed\n");
           exit(1);
       }
diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
index c95e6e2..8e1c417 100644
--- a/hw/i386/pc_q35.c
+++ b/hw/i386/pc_q35.c
@@ -120,8 +120,8 @@ static void pc_q35_init(QEMUMachineInitArgs *args)
           below_4g_mem_size = args->ram_size;
       }
   -    if (xen_enabled() && xen_hvm_init(&below_4g_mem_size,
&above_4g_mem_size,
-                                      &ram_memory) != 0) {
+    if (xen_enabled() && xen_hvm_init(max_ram_below_4g,
&below_4g_mem_size,
+                                      &above_4g_mem_size, &ram_memory) !=
0) {
           fprintf(stderr, "xen hardware virtual machine initialisation
failed\n");
           exit(1);
       }
diff --git a/include/hw/xen/xen.h b/include/hw/xen/xen.h
index 0769db2..fda559a 100644
--- a/include/hw/xen/xen.h
+++ b/include/hw/xen/xen.h
@@ -41,8 +41,8 @@ int xen_init(QEMUMachine *machine);
   void xenstore_store_pv_console_info(int i, struct CharDriverState *chr);
     #if defined(NEED_CPU_H) && !defined(CONFIG_USER_ONLY)
-int xen_hvm_init(ram_addr_t *below_4g_mem_size, ram_addr_t
*above_4g_mem_size,
-                 MemoryRegion **ram_memory);
+int xen_hvm_init(ram_addr_t max_ram_below_4g, ram_addr_t
*below_4g_mem_size,
+                 ram_addr_t *above_4g_mem_size, MemoryRegion
**ram_memory);
   void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size,
                      struct MemoryRegion *mr);
   void xen_modified_memory(ram_addr_t start, ram_addr_t length);
diff --git a/xen-all.c b/xen-all.c
index c64300c..48ba335 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -155,32 +155,34 @@ qemu_irq *xen_interrupt_controller_init(void)
     /* Memory Ops */
   -static void xen_ram_init(ram_addr_t *below_4g_mem_size,
+static void xen_ram_init(ram_addr_t ram_size, ram_addr_t
max_ram_below_4g,
+                         ram_addr_t *below_4g_mem_size,
                            ram_addr_t *above_4g_mem_size,
-                         ram_addr_t ram_size, MemoryRegion
**ram_memory_p)
+                         MemoryRegion **ram_memory_p)
   {
       MemoryRegion *sysmem = get_system_memory();
       ram_addr_t block_len;
   -    block_len = ram_size;
-    if (ram_size >= HVM_BELOW_4G_RAM_END) {
-        /* Xen does not allocate the memory continuously, and keep a hole
at
-         * HVM_BELOW_4G_MMIO_START of HVM_BELOW_4G_MMIO_LENGTH
-         */
-        block_len += HVM_BELOW_4G_MMIO_LENGTH;
+    if (!max_ram_below_4g) {
+        if (ram_size >= HVM_BELOW_4G_RAM_END) {
+            *above_4g_mem_size = ram_size - HVM_BELOW_4G_RAM_END;
+            *below_4g_mem_size = HVM_BELOW_4G_RAM_END;
+        } else {
+            *above_4g_mem_size = 0;
+            *below_4g_mem_size = ram_size;
+        }
+    }
Instead of treating max_ram_below_4g as a special case, couldn't
initialize it to HVM_BELOW_4G_RAM_END?
Since max_ram_below_4g is used and initialize in normal QEMU code
where HVM_BELOW_4G_RAM_END is not defined, I do not see how to
do this outside of this routine without adding a new routine for this.
You can simply do this at the beginning of xen_ram_init:

max_ram_below_4g = max_ram_below_4g ? max_ram_below_4g : HVM_BELOW_4G_RAM_END;

my comment was about code readability, I didn't mean change any
functionalities.

So the partial code delta:

     MemoryRegion *sysmem = get_system_memory();
     ram_addr_t block_len;

-    block_len = ram_size;
-    if (ram_size >= HVM_BELOW_4G_RAM_END) {
-        /* Xen does not allocate the memory continuously, and keep a hole at
-         * HVM_BELOW_4G_MMIO_START of HVM_BELOW_4G_MMIO_LENGTH
-         */
-        block_len += HVM_BELOW_4G_MMIO_LENGTH;
-    }
-    memory_region_init_ram(&ram_memory, NULL, "xen.ram", block_len);
-    *ram_memory_p = &ram_memory;
-    vmstate_register_ram_global(&ram_memory);
-
-    if (ram_size >= HVM_BELOW_4G_RAM_END) {
-        *above_4g_mem_size = ram_size - HVM_BELOW_4G_RAM_END;
-        *below_4g_mem_size = HVM_BELOW_4G_RAM_END;
+    max_ram_below_4g = max_ram_below_4g ? max_ram_below_4g : 
HVM_BELOW_4G_RAM_END;
+    if (ram_size >= max_ram_below_4g) {
+        *above_4g_mem_size = ram_size - max_ram_below_4g;
+        *below_4g_mem_size = max_ram_below_4g;
     } else {
         *above_4g_mem_size = 0;
         *below_4g_mem_size = ram_size;
     }
+    if (!*above_4g_mem_size) {
+        block_len = ram_size;
+    } else {
+        /* Xen does not allocate the memory continuously, and keep a hole of
+         * of the size computed above or passed in. */
+        block_len = (1ULL << 32) + *above_4g_mem_size;
+    }
+    memory_region_init_ram(&ram_memory, NULL, "xen.ram", block_len);
+    *ram_memory_p = &ram_memory;
+    vmstate_register_ram_global(&ram_memory);


Which does redo the calculation of above and below when max_ram_below_4g
is set, is better for code readability.

I am happy to send a v2 with this, just do not want to send too many versions.

   -Don Slutz




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