[Qemu-devel] [PATCH 1/1] pc & q35: fix handling of lowmem

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[Qemu-devel] [PATCH 1/1] pc & q35: fix handling of lowmem

From:	Don Slutz
Subject:	[Qemu-devel] [PATCH 1/1] pc & q35: fix handling of lowmem
Date:	Thu, 27 Feb 2014 15:01:02 -0500

Without this, asking for 3.25G on memory for pc-i440fx-2.0 does not
adjust the pci hole to start at 3G.  Asking for 3.75G does do this
adjustment.

Here is what the current code does:

out/x86_64-softmmu/qemu-system-x86_64 -serial pty ~/qemu-img/Lin-Net-disk1.raw 
-machine pc-i440fx-2.0 -m 3.75G

BIOS-provided physical RAM map:
 BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
 BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
 BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
 BIOS-e820: 0000000000100000 - 00000000bfffe000 (usable)
 BIOS-e820: 00000000bfffe000 - 00000000c0000000 (reserved)
 BIOS-e820: 00000000feffc000 - 00000000ff000000 (reserved)
 BIOS-e820: 00000000fffc0000 - 0000000100000000 (reserved)
 BIOS-e820: 0000000100000000 - 0000000130000000 (usable)

out/x86_64-softmmu/qemu-system-x86_64 -serial pty ~/qemu-img/Lin-Net-disk1.raw 
-machine pc-i440fx-1.7 -m 3.75G

BIOS-provided physical RAM map:
 BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
 BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
 BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
 BIOS-e820: 0000000000100000 - 00000000dfffe000 (usable)
 BIOS-e820: 00000000dfffe000 - 00000000e0000000 (reserved)
 BIOS-e820: 00000000feffc000 - 00000000ff000000 (reserved)
 BIOS-e820: 00000000fffc0000 - 0000000100000000 (reserved)
 BIOS-e820: 0000000100000000 - 0000000110000000 (usable)

out/x86_64-softmmu/qemu-system-x86_64 -serial pty ~/qemu-img/Lin-Net-disk1.raw 
-machine pc-i440fx-2.0 -m 3.25G

BIOS-provided physical RAM map:
 BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
 BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
 BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
 BIOS-e820: 0000000000100000 - 00000000cfffe000 (usable)
 BIOS-e820: 00000000cfffe000 - 00000000d0000000 (reserved)
 BIOS-e820: 00000000feffc000 - 00000000ff000000 (reserved)
 BIOS-e820: 00000000fffc0000 - 0000000100000000 (reserved)

out/x86_64-softmmu/qemu-system-x86_64 -serial pty ~/qemu-img/Lin-Net-disk1.raw 
-machine pc-i440fx-1.7 -m 3.25G

BIOS-provided physical RAM map:
 BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
 BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
 BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
 BIOS-e820: 0000000000100000 - 00000000cfffe000 (usable)
 BIOS-e820: 00000000cfffe000 - 00000000d0000000 (reserved)
 BIOS-e820: 00000000feffc000 - 00000000ff000000 (reserved)
 BIOS-e820: 00000000fffc0000 - 0000000100000000 (reserved)

After this patch:

out/x86_64-softmmu/qemu-system-x86_64 -serial pty ~/qemu-img/Lin-Net-disk1.raw 
-machine pc-i440fx-2.0 -m 3.75G

BIOS-provided physical RAM map:
 BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
 BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
 BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
 BIOS-e820: 0000000000100000 - 00000000bfffe000 (usable)
 BIOS-e820: 00000000bfffe000 - 00000000c0000000 (reserved)
 BIOS-e820: 00000000fffc0000 - 0000000100000000 (reserved)
 BIOS-e820: 0000000100000000 - 0000000130000000 (usable)

out/x86_64-softmmu/qemu-system-x86_64 -serial pty ~/qemu-img/Lin-Net-disk1.raw 
-machine pc-i440fx-1.7 -m 3.75G

BIOS-provided physical RAM map:
 BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
 BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
 BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
 BIOS-e820: 0000000000100000 - 00000000dfffe000 (usable)
 BIOS-e820: 00000000dfffe000 - 00000000e0000000 (reserved)
 BIOS-e820: 00000000fffc0000 - 0000000100000000 (reserved)
 BIOS-e820: 0000000100000000 - 0000000110000000 (usable)

out/x86_64-softmmu/qemu-system-x86_64 -serial pty ~/qemu-img/Lin-Net-disk1.raw 
-machine pc-i440fx-2.0 -m 3.25G

BIOS-provided physical RAM map:
 BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
 BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
 BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
 BIOS-e820: 0000000000100000 - 00000000bfffe000 (usable)
 BIOS-e820: 00000000bfffe000 - 00000000c0000000 (reserved)
 BIOS-e820: 00000000fffc0000 - 0000000100000000 (reserved)
 BIOS-e820: 0000000100000000 - 0000000110000000 (usable)

out/x86_64-softmmu/qemu-system-x86_64 -serial pty ~/qemu-img/Lin-Net-disk1.raw 
-machine pc-i440fx-1.7 -m 3.25G

BIOS-provided physical RAM map:
 BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
 BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
 BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
 BIOS-e820: 0000000000100000 - 00000000cfffe000 (usable)
 BIOS-e820: 00000000cfffe000 - 00000000d0000000 (reserved)
 BIOS-e820: 00000000fffc0000 - 0000000100000000 (reserved)

Signed-off-by: Don Slutz <address@hidden>
---
 hw/i386/pc_piix.c | 13 ++++++++-----
 hw/i386/pc_q35.c  | 17 ++++++++++-------
 2 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index d5dc1ef..4e63d8f 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -95,6 +95,11 @@ static void pc_init1(QEMUMachineInitArgs *args,
     DeviceState *icc_bridge;
     FWCfgState *fw_cfg = NULL;
     PcGuestInfo *guest_info;
+    /*
+     * For old machine types, use whatever split we used historically to avoid
+     * breaking migration.
+     */
+    ram_addr_t lowmem = gigabyte_align ? 0xc0000000 : 0xe0000000;
 
     if (xen_enabled() && xen_hvm_init(&ram_memory) != 0) {
         fprintf(stderr, "xen hardware virtual machine initialisation 
failed\n");
@@ -111,15 +116,13 @@ static void pc_init1(QEMUMachineInitArgs *args,
         kvmclock_create();
     }
 
-    /* Check whether RAM fits below 4G (leaving 1/2 GByte for IO memory).
+    /* Check whether RAM fits below 4G (leaving 1/2 GByte for IO memory (old)
+     * or 1 GByte for IO memory (new)).
      * If it doesn't, we need to split it in chunks below and above 4G.
      * In any case, try to make sure that guest addresses aligned at
      * 1G boundaries get mapped to host addresses aligned at 1G boundaries.
-     * For old machine types, use whatever split we used historically to avoid
-     * breaking migration.
      */
-    if (args->ram_size >= 0xe0000000) {
-        ram_addr_t lowmem = gigabyte_align ? 0xc0000000 : 0xe0000000;
+    if (args->ram_size >= lowmem) {
         above_4g_mem_size = args->ram_size - lowmem;
         below_4g_mem_size = lowmem;
     } else {
diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
index a7f6260..2627927 100644
--- a/hw/i386/pc_q35.c
+++ b/hw/i386/pc_q35.c
@@ -82,6 +82,11 @@ static void pc_q35_init(QEMUMachineInitArgs *args)
     PCIDevice *ahci;
     DeviceState *icc_bridge;
     PcGuestInfo *guest_info;
+    /*
+     * For old machine types, use whatever split we used historically to avoid
+     * breaking migration.
+     */
+    ram_addr_t lowmem = gigabyte_align ? 0x80000000 : 0xb0000000;
 
     if (xen_enabled() && xen_hvm_init(&ram_memory) != 0) {
         fprintf(stderr, "xen hardware virtual machine initialisation 
failed\n");
@@ -97,17 +102,15 @@ static void pc_q35_init(QEMUMachineInitArgs *args)
 
     kvmclock_create();
 
-    /* Check whether RAM fits below 4G (leaving 1/2 GByte for IO memory
-     * and 256 Mbytes for PCI Express Enhanced Configuration Access Mapping
-     * also known as MMCFG).
+    /* Check whether RAM fits below 4G (leaving 1 and 3/8 GByte for
+     * IO memory and 256 Mbytes for PCI Express Enhanced
+     * Configuration Access Mapping also known as MMCFG (old) or
+     * leaving 2 GByte for IO memory (new)).
      * If it doesn't, we need to split it in chunks below and above 4G.
      * In any case, try to make sure that guest addresses aligned at
      * 1G boundaries get mapped to host addresses aligned at 1G boundaries.
-     * For old machine types, use whatever split we used historically to avoid
-     * breaking migration.
      */
-    if (args->ram_size >= 0xb0000000) {
-        ram_addr_t lowmem = gigabyte_align ? 0x80000000 : 0xb0000000;
+    if (args->ram_size >= lowmem) {
         above_4g_mem_size = args->ram_size - lowmem;
         below_4g_mem_size = lowmem;
     } else {
-- 
1.8.4

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[Qemu-devel] [PATCH 1/1] pc & q35: fix handling of lowmem, Don Slutz <=
- Re: [Qemu-devel] [PATCH 1/1] pc & q35: fix handling of lowmem, Gerd Hoffmann, 2014/02/28
  - Re: [Qemu-devel] [PATCH 1/1] pc & q35: fix handling of lowmem, Don Slutz, 2014/02/28

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