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Re: [Qemu-devel] [PATCH v5 2/3] pc & q35: Add new machine opt max-ram-be
From: |
Marcel Apfelbaum |
Subject: |
Re: [Qemu-devel] [PATCH v5 2/3] pc & q35: Add new machine opt max-ram-below-4g |
Date: |
Mon, 09 Jun 2014 18:10:27 +0300 |
Hi,
On Mon, 2014-06-09 at 17:38 +0300, Michael S. Tsirkin wrote:
> On Mon, Jun 09, 2014 at 10:20:57AM -0400, Don Slutz wrote:
> > On 06/08/14 11:40, Michael S. Tsirkin wrote:
> > >On Fri, Jun 06, 2014 at 01:52:05PM -0400, Don Slutz wrote:
> > >>This is a pc & q35 only machine opt. One use is to allow for more
> > >>ram in a 32bit guest for example:
> > >>
> > >>-machine pc,max-ram-below-4g=3.75G
> > >>
> > >>If you add enough PCI devices then all mmio for them will not fit
> > >>below 4G which may not be the layout the user wanted. This allows
> > >>you to increase the below 4G address space that PCI devices can use
> > >>(aka decrease ram below 4G) and therefore in more cases not have any
> > >>mmio that is above 4G.
> > >>
> > >>For example using "-machine pc,max-ram-below-4g=2G" on the command
> > >>line will limit the amount of ram that is below 4G to 2G.
> > >>
> > >>Signed-off-by: Don Slutz <address@hidden>
> > >>---
> > >>v5:
> > >> Re-work based on:
> > >>
> > >> https://github.com/imammedo/qemu/commits/memory-hotplug-v11
> > >>
> > >>
> > >> hw/i386/pc.c | 38 ++++++++++++++++++++++++++++++++++++++
> > >> hw/i386/pc_piix.c | 15 ++++++++++++---
> > >> hw/i386/pc_q35.c | 15 ++++++++++++---
> > >> include/hw/i386/pc.h | 3 +++
> > >> vl.c | 4 ++++
> > >> 5 files changed, 69 insertions(+), 6 deletions(-)
> > >>
> > >>diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> > >>index 7cdba10..bccb746 100644
> > >>--- a/hw/i386/pc.c
> > >>+++ b/hw/i386/pc.c
> > >>@@ -1644,11 +1644,49 @@ pc_machine_get_hotplug_memory_region_size(Object
> > >>*obj, Visitor *v, void *opaque,
> > >> visit_type_int(v, &value, name, errp);
> > >> }
> > >>+static void pc_machine_get_max_ram_below_4g(Object *obj, Visitor *v,
> > >>+ void *opaque, const char *name,
> > >>+ Error **errp)
> > >>+{
> > >>+ PCMachineState *pcms = PC_MACHINE(obj);
> > >>+ uint64_t value = pcms->max_ram_below_4g;
> > >>+
> > >>+ visit_type_size(v, &value, name, errp);
> > >>+}
> > >>+
> > >>+static void pc_machine_set_max_ram_below_4g(Object *obj, Visitor *v,
> > >>+ void *opaque, const char *name,
> > >>+ Error **errp)
> > >>+{
> > >>+ PCMachineState *pcms = PC_MACHINE(obj);
> > >>+ Error *error = NULL;
> > >>+ uint64_t value;
> > >>+
> > >>+ visit_type_size(v, &value, name, &error);
> > >>+ if (error) {
> > >>+ error_propagate(errp, error);
> > >>+ return;
> > >>+ }
> > >>+ if (value > (1ULL << 32)) {
> > >>+ error_set(&error, ERROR_CLASS_GENERIC_ERROR,
> > >>+ "Machine option 'max-ram-below-4g=%"PRIu64
> > >>+ "' expects size less then or equal to 4G", value);
> > >less than
> >
> > But the test is greater then. So "not greater then" is "less then or
> > equal".
> > Or did you want the test changed?
>
> No, just correcting English: less than, not less then :)
>
> > >>+ error_propagate(errp, error);
> > >>+ return;
> > >>+ }
> > >>+
> > >>+ pcms->max_ram_below_4g = value;
> > >>+}
> > >>+
> > >> static void pc_machine_initfn(Object *obj)
> > >> {
> > >> object_property_add(obj, PC_MACHINE_MEMHP_REGION_SIZE, "int",
> > >> pc_machine_get_hotplug_memory_region_size,
> > >> NULL, NULL, NULL, NULL);
> > >>+ 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,
> > >>+ NULL, NULL, NULL);
Maybe you can add here a sane default and avoid comparison with 0
any time you use it.
If you think you need value per machine type, you can add it to
compat props. I don't see how is related, so you may not want to do so.
> > >> }
> > >> static void pc_machine_class_init(ObjectClass *oc, void *data)
> > >>diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> > >>index 40f6eaf..25f4727 100644
> > >>--- a/hw/i386/pc_piix.c
> > >>+++ b/hw/i386/pc_piix.c
> > >>@@ -98,6 +98,13 @@ static void pc_init1(MachineState *machine,
> > >> DeviceState *icc_bridge;
> > >> FWCfgState *fw_cfg = NULL;
> > >> PcGuestInfo *guest_info;
> > >>+ Object *mo = qdev_get_machine();
> > >>+ PCMachineState *pcms = PC_MACHINE(mo);
> > >>+ ram_addr_t lowmem = 0xe0000000;
> > >>+
> > >>+ if (pcms && pcms->max_ram_below_4g) {
>From my QOM understanding, max_ram_below_4g is a private field,
so it not should be used directly.
You can use QOMs object_property_get or add a pc_machine wrapper
for getting/setting the field.
> > >Is pcms ever NULL? If yes why?
> >
> > Not that I know of. I would be happy to convert this to an assert(pcms).
>
> In fact, PC_MACHINE already includes an assert doesn't it?
> So no need to check it everywhere.
+1. No need for assert here. Is already done by OBJECT_CHECK.
Hope I helped,
Marcel
>
> > >>+ lowmem = pcms->max_ram_below_4g;
> > >>+ }
> > >> /* Check whether RAM fits below 4G (leaving 1/2 GByte for IO
> > >> memory).
> > >> * If it doesn't, we need to split it in chunks below and above 4G.
> > >>@@ -106,8 +113,10 @@ static void pc_init1(MachineState *machine,
> > >> * For old machine types, use whatever split we used historically
> > >> to avoid
> > >> * breaking migration.
> > >> */
> > >>- if (machine->ram_size >= 0xe0000000) {
> > >>- ram_addr_t lowmem = gigabyte_align ? 0xc0000000 : 0xe0000000;
> > >>+ if (machine->ram_size >= lowmem) {
> > >>+ if (!(pcms && pcms->max_ram_below_4g) && gigabyte_align) {
> > >>+ lowmem = 0xc0000000;
> > >>+ }
> > >> above_4g_mem_size = machine->ram_size - lowmem;
> > >> below_4g_mem_size = lowmem;
> > >> } else {
> > >
> > >So why do we need gigabyte_align anymore?
> >
> > Because of qemu 2.0 and the user is not required to specify this option.
> >
> > >Can't we set property to 0xc0000000 by default, and
> > >override for old machine types?
> >
> > There is a strange compatibility part here. Since this code includes
> > ram_size (see:
> >
> > http://lists.gnu.org/archive/html/qemu-devel/2014-02/msg05146.html
> >
> > ) and xen has a different default.
> >
>
> So instead of default 0, it would be preferable to set the default to the
> actual value, and let user override it.
>
> Or if that's too hard, set max_ram_below_4g instead of setting
> gigabyte_align. gigabyte_align switches everywhere is messy
> enough, adding max_ram_below_4g into mix is just too messy.
>
>
>
> > >Also, a value that isn't a multiple of 1G will lead to bad
> > >performance for large machines which do have above_4g_mem_size.
> > >Let's detect and print a warning.
> >
> > Will Do.
> >
> > -Don Slutz
> >
> > >
> > >
> > >>@@ -122,7 +131,7 @@ static void pc_init1(MachineState *machine,
> > >> }
> > >> icc_bridge = qdev_create(NULL, TYPE_ICC_BRIDGE);
> > >>- object_property_add_child(qdev_get_machine(), "icc-bridge",
> > >>+ object_property_add_child(mo, "icc-bridge",
> > >> OBJECT(icc_bridge), NULL);
> > >> pc_cpus_init(machine->cpu_model, icc_bridge);
> > >>diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
> > >>index e28ce40..155cdf1 100644
> > >>--- a/hw/i386/pc_q35.c
> > >>+++ b/hw/i386/pc_q35.c
> > >>@@ -85,6 +85,13 @@ static void pc_q35_init(MachineState *machine)
> > >> PCIDevice *ahci;
> > >> DeviceState *icc_bridge;
> > >> PcGuestInfo *guest_info;
> > >>+ Object *mo = qdev_get_machine();
> > >>+ PCMachineState *pcms = PC_MACHINE(mo);
> > >>+ ram_addr_t lowmem = 0xb0000000;
> > >>+
> > >>+ if (pcms && pcms->max_ram_below_4g) {
> > >>+ lowmem = pcms->max_ram_below_4g;
> > >>+ }
> > >> /* Check whether RAM fits below 4G (leaving 1/2 GByte for IO memory
> > >> * and 256 Mbytes for PCI Express Enhanced Configuration Access
> > >> Mapping
> > >>@@ -95,8 +102,10 @@ static void pc_q35_init(MachineState *machine)
> > >> * For old machine types, use whatever split we used historically
> > >> to avoid
> > >> * breaking migration.
> > >> */
> > >>- if (machine->ram_size >= 0xb0000000) {
> > >>- ram_addr_t lowmem = gigabyte_align ? 0x80000000 : 0xb0000000;
> > >>+ if (machine->ram_size >= lowmem) {
> > >>+ if (!(pcms && pcms->max_ram_below_4g) && gigabyte_align) {
> > >>+ lowmem = 0x800000000;
> > >>+ }
> > >> above_4g_mem_size = machine->ram_size - lowmem;
> > >> below_4g_mem_size = lowmem;
> > >> } else {
> > >>@@ -111,7 +120,7 @@ static void pc_q35_init(MachineState *machine)
> > >> }
> > >> icc_bridge = qdev_create(NULL, TYPE_ICC_BRIDGE);
> > >>- object_property_add_child(qdev_get_machine(), "icc-bridge",
> > >>+ object_property_add_child(mo, "icc-bridge",
> > >> OBJECT(icc_bridge), NULL);
> > >> pc_cpus_init(machine->cpu_model, icc_bridge);
> > >>diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> > >>index 19530bd..2d8b562 100644
> > >>--- a/include/hw/i386/pc.h
> > >>+++ b/include/hw/i386/pc.h
> > >>@@ -32,10 +32,13 @@ struct PCMachineState {
> > >> MemoryRegion hotplug_memory;
> > >> HotplugHandler *acpi_dev;
> > >>+
> > >>+ uint64_t max_ram_below_4g;
> > >> };
> > >> #define PC_MACHINE_ACPI_DEVICE_PROP "acpi-device"
> > >> #define PC_MACHINE_MEMHP_REGION_SIZE "hotplug-memory-region-size"
> > >>+#define PC_MACHINE_MAX_RAM_BELOW_4G "max-ram-below-4g"
> > >> /**
> > >> * PCMachineClass:
> > >>diff --git a/vl.c b/vl.c
> > >>index 5e77a27..cffb9c5 100644
> > >>--- a/vl.c
> > >>+++ b/vl.c
> > >>@@ -382,6 +382,10 @@ static QemuOptsList qemu_machine_opts = {
> > >> .name = "kvm-type",
> > >> .type = QEMU_OPT_STRING,
> > >> .help = "Specifies the KVM virtualization mode (HV, PR)",
> > >>+ },{
> > >>+ .name = PC_MACHINE_MAX_RAM_BELOW_4G,
> > >>+ .type = QEMU_OPT_SIZE,
> > >>+ .help = "maximum ram below the 4G boundary (32bit boundary)",
> > >> },
> > >> { /* End of list */ }
> > >> },
> > >>--
> > >>1.8.4
>
- [Qemu-devel] [PATCH v5 0/3] Add max-ram-below-4g (was Add pci_hole_min_size machine option), Don Slutz, 2014/06/06
- [Qemu-devel] [PATCH v5 1/3] xen-hvm: Fix xen_hvm_init() to adjust pc memory layout, Don Slutz, 2014/06/06
- [Qemu-devel] [PATCH v5 2/3] pc & q35: Add new machine opt max-ram-below-4g, Don Slutz, 2014/06/06
- Re: [Qemu-devel] [PATCH v5 2/3] pc & q35: Add new machine opt max-ram-below-4g, Michael S. Tsirkin, 2014/06/08
- Re: [Qemu-devel] [PATCH v5 2/3] pc & q35: Add new machine opt max-ram-below-4g, Don Slutz, 2014/06/09
- Re: [Qemu-devel] [PATCH v5 2/3] pc & q35: Add new machine opt max-ram-below-4g, Michael S. Tsirkin, 2014/06/09
- Re: [Qemu-devel] [PATCH v5 2/3] pc & q35: Add new machine opt max-ram-below-4g,
Marcel Apfelbaum <=
- Re: [Qemu-devel] [PATCH v5 2/3] pc & q35: Add new machine opt max-ram-below-4g, Igor Mammedov, 2014/06/09
- Re: [Qemu-devel] [PATCH v5 2/3] pc & q35: Add new machine opt max-ram-below-4g, Marcel Apfelbaum, 2014/06/09
- Re: [Qemu-devel] [PATCH v5 2/3] pc & q35: Add new machine opt max-ram-below-4g, Don Slutz, 2014/06/09
- Re: [Qemu-devel] [PATCH v5 2/3] pc & q35: Add new machine opt max-ram-below-4g, Don Slutz, 2014/06/09
- Re: [Qemu-devel] [PATCH v5 2/3] pc & q35: Add new machine opt max-ram-below-4g, Gerd Hoffmann, 2014/06/10
- Re: [Qemu-devel] [PATCH v5 2/3] pc & q35: Add new machine opt max-ram-below-4g, Don Slutz, 2014/06/17
- Re: [Qemu-devel] [PATCH v5 2/3] pc & q35: Add new machine opt max-ram-below-4g, Gerd Hoffmann, 2014/06/18
Re: [Qemu-devel] [PATCH v5 2/3] pc & q35: Add new machine opt max-ram-below-4g, Michael S. Tsirkin, 2014/06/17