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xen: fix ram init regression

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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.perard@citrix.com>
Tested-by: Anthony PERARD <anthony.perard@citrix.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Gerd Hoffmann 2016-06-24 13:35:17 +02:00 committed by Michael S. Tsirkin
parent e2c8f9e44e
commit 5ec7d09818
4 changed files with 36 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
hw/i386/pc.c
View File

@ -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,

52
hw/i386/pc_piix.c
View File

@ -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 (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);
} 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;
}
}
pc_cpus_init(pcms);

3
hw/i386/pc_q35.c
View File

@ -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 &&

3
xen-hvm.c
View File

@ -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;
}