From: Gerd Hoffmann <kra...@redhat.com>
Commit "8156d48 pc: allow raising low memory via max-ram-below-4g
option" causes a regression on xen, because it uses a different
memory split.
This patch initializes max-ram-below-4g to zero and leaves the
initialization to the memory initialization functions. That way
they can pick different default values (max-ram-below-4g is zero
still) or use the user supplied value (max-ram-below-4g is non-zero).
Also skip the whole ram split calculation on Xen. xen_ram_init()
does its own split calculation anyway so it is superfluous, also
this way xen_ram_init can actually see whenever max-ram-below-4g
is zero or not.
Reported-by: Anthony PERARD <anthony.per...@citrix.com>
Tested-by: Anthony PERARD <anthony.per...@citrix.com>
Signed-off-by: Gerd Hoffmann <kra...@redhat.com>
Reviewed-by: Michael S. Tsirkin <m...@redhat.com>
Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
---
hw/i386/pc.c | 2 +-
hw/i386/pc_piix.c | 50 ++++++++++++++++++++++++++++----------------------
hw/i386/pc_q35.c | 3 +++
xen-hvm.c | 3 +++
4 files changed, 35 insertions(+), 23 deletions(-)
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 44a8f3b..cd1745e 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1919,7 +1919,7 @@ static void pc_machine_initfn(Object *obj)
pc_machine_get_hotplug_memory_region_size,
NULL, NULL, NULL, &error_abort);
- pcms->max_ram_below_4g = 0xe0000000; /* 3.5G */
+ pcms->max_ram_below_4g = 0; /* use default */
object_property_add(obj, PC_MACHINE_MAX_RAM_BELOW_4G, "size",
pc_machine_get_max_ram_below_4g,
pc_machine_set_max_ram_below_4g,
diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index c7d70af..a07dc81 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -108,37 +108,43 @@ static void pc_init1(MachineState *machine,
* so legacy non-PAE guests can get as much memory as possible in
* the 32bit address space below 4G.
*
+ * - Note that Xen has its own ram setp code in xen_ram_init(),
+ * called via xen_hvm_init().
+ *
* Examples:
* qemu -M pc-1.7 -m 4G (old default) -> 3584M low, 512M high
* qemu -M pc -m 4G (new default) -> 3072M low, 1024M high
* qemu -M pc,max-ram-below-4g=2G -m 4G -> 2048M low, 2048M high
* qemu -M pc,max-ram-below-4g=4G -m 3968M -> 3968M low (=4G-128M)
*/
- lowmem = pcms->max_ram_below_4g;
- if (machine->ram_size >= pcms->max_ram_below_4g) {
- if (pcmc->gigabyte_align) {
- if (lowmem > 0xc0000000) {
- lowmem = 0xc0000000;
- }
- if (lowmem & ((1ULL << 30) - 1)) {
- error_report("Warning: Large machine and max_ram_below_4g "
- "(%" PRIu64 ") not a multiple of 1G; "
- "possible bad performance.",
- pcms->max_ram_below_4g);
+ if (xen_enabled()) {
+ xen_hvm_init(pcms, &ram_memory);
+ } else {
+ if (!pcms->max_ram_below_4g) {
+ pcms->max_ram_below_4g = 0xe0000000; /* default: 3.5G */
+ }
+ lowmem = pcms->max_ram_below_4g;
+ if (machine->ram_size >= pcms->max_ram_below_4g) {
+ if (pcmc->gigabyte_align) {
+ if (lowmem > 0xc0000000) {
+ lowmem = 0xc0000000;
+ }
+ if (lowmem & ((1ULL << 30) - 1)) {
+ error_report("Warning: Large machine and max_ram_below_4g "
+ "(%" PRIu64 ") not a multiple of 1G; "
+ "possible bad performance.",
+ pcms->max_ram_below_4g);
+ }
}
}
- }
- if (machine->ram_size >= lowmem) {
- pcms->above_4g_mem_size = machine->ram_size - lowmem;
- pcms->below_4g_mem_size = lowmem;
- } else {
- pcms->above_4g_mem_size = 0;
- pcms->below_4g_mem_size = machine->ram_size;
- }
-
- if (xen_enabled()) {
- xen_hvm_init(pcms, &ram_memory);
+ if (machine->ram_size >= lowmem) {
+ pcms->above_4g_mem_size = machine->ram_size - lowmem;
+ pcms->below_4g_mem_size = lowmem;
+ } else {
+ pcms->above_4g_mem_size = 0;
+ pcms->below_4g_mem_size = machine->ram_size;
+ }
}
pc_cpus_init(pcms);
diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
index 04b2684..cd57bce 100644
--- a/hw/i386/pc_q35.c
+++ b/hw/i386/pc_q35.c
@@ -94,6 +94,9 @@ static void pc_q35_init(MachineState *machine)
/* Handle the machine opt max-ram-below-4g. It is basically doing
* min(qemu limit, user limit).
*/
+ if (!pcms->max_ram_below_4g) {
+ pcms->max_ram_below_4g = 1ULL << 32; /* default: 4G */;
+ }
if (lowmem > pcms->max_ram_below_4g) {
lowmem = pcms->max_ram_below_4g;
if (machine->ram_size - lowmem > lowmem &&
diff --git a/xen-hvm.c b/xen-hvm.c
index 98ea44f..eb57792 100644
--- a/xen-hvm.c
+++ b/xen-hvm.c
@@ -190,6 +190,9 @@ static void xen_ram_init(PCMachineState *pcms,
/* Handle the machine opt max-ram-below-4g. It is basically doing
* min(xen limit, user limit).
*/
+ if (!user_lowmem) {
+ user_lowmem = HVM_BELOW_4G_RAM_END; /* default */
+ }
if (HVM_BELOW_4G_RAM_END <= user_lowmem) {
user_lowmem = HVM_BELOW_4G_RAM_END;
}
--
MST
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