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Re: [Qemu-devel] [PATCH 2.1 v7 2/3] pc & q35: Add new machine opt max-ra
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH 2.1 v7 2/3] pc & q35: Add new machine opt max-ram-below-4g |
Date: |
Mon, 23 Jun 2014 17:59:48 +0300 |
On Thu, Jun 19, 2014 at 09:40:25PM -0400, Don Slutz wrote:
> This is a pc & q35 only machine opt.
>
> 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.
>
> Note: this machine option cannot be used to increase the amount
> of ram below 4G.
>
> Signed-off-by: Don Slutz <address@hidden>
> ---
> v7:
> Drop most of v5 to v6 changes.
> default: max-ram-below-4g=4g
> pc & q35:
> calculate lowmem
> lowmem = MIN(lowmem, max-ram-below-4g)
> calculate above_4g_mem_size and below_4g_mem_size
> v6:
> Added setting of .default_machine_opts to include max-ram-below-4g
> for all pc types.
> Removed gigabyte_align
> Added warning on small value.
> "less then" to "less than"
>
> v5:
> Re-work based on:
>
> https://github.com/imammedo/qemu/commits/memory-hotplug-v11
>
>
> hw/i386/pc.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
> hw/i386/pc_piix.c | 22 +++++++++++++++++++++-
> hw/i386/pc_q35.c | 22 +++++++++++++++++++++-
> include/hw/i386/pc.h | 3 +++
> vl.c | 4 ++++
> 5 files changed, 96 insertions(+), 2 deletions(-)
>
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index e993b0f..bc15761 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -1647,11 +1647,58 @@ 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 than or equal to 4G", value);
> + error_propagate(errp, error);
> + return;
> + }
> +
> + if (value < (1ULL << 20)) {
> + error_report("Warning: small max_ram_below_4g(%"PRIu64
> + ") less than 1M. BIOS may not work..",
> + value);
> + }
> +
> + pcms->max_ram_below_4g = value;
> +}
> +
> static void pc_machine_initfn(Object *obj)
> {
> + PCMachineState *pcms = PC_MACHINE(obj);
> +
> object_property_add(obj, PC_MACHINE_MEMHP_REGION_SIZE, "int",
> pc_machine_get_hotplug_memory_region_size,
> NULL, NULL, NULL, NULL);
> + pcms->max_ram_below_4g = 1UL << 32; /* 4G */
This is a bug: should be 1ULL. Fixed it up locally.
> + 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);
> }
>
> 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 60057f9..b4ce10e 100644
> --- a/hw/i386/pc_piix.c
> +++ b/hw/i386/pc_piix.c
> @@ -48,6 +48,7 @@
> #include "exec/address-spaces.h"
> #include "hw/acpi/acpi.h"
> #include "cpu.h"
> +#include "qemu/error-report.h"
> #ifdef CONFIG_XEN
> # include <xen/hvm/hvm_info_table.h>
> #endif
> @@ -98,6 +99,7 @@ static void pc_init1(MachineState *machine,
> DeviceState *icc_bridge;
> FWCfgState *fw_cfg = NULL;
> PcGuestInfo *guest_info;
> + ram_addr_t lowmem;
>
> /* 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.
> @@ -107,7 +109,25 @@ static void pc_init1(MachineState *machine,
> * breaking migration.
> */
> if (machine->ram_size >= 0xe0000000) {
> - ram_addr_t lowmem = gigabyte_align ? 0xc0000000 : 0xe0000000;
> + lowmem = gigabyte_align ? 0xc0000000 : 0xe0000000;
> + } else {
> + lowmem = 0xe0000000;
> + }
> +
> + /* Handle the machine opt max-ram-below-4g. It is basicly doing
> + * min(qemu limit, user limit).
> + */
> + if (lowmem > pc_machine->max_ram_below_4g) {
> + lowmem = pc_machine->max_ram_below_4g;
> + if (machine->ram_size - lowmem > lowmem &&
> + lowmem & ((1ULL << 30) - 1)) {
> + error_report("Warning: Large machine and
> max_ram_below_4g(%"PRIu64
> + ") not a multiple of 1G; possible bad performance.",
> + pc_machine->max_ram_below_4g);
> + }
> + }
> +
> + if (machine->ram_size >= lowmem) {
> above_4g_mem_size = machine->ram_size - lowmem;
> below_4g_mem_size = lowmem;
> } else {
> diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
> index 2cb743c..c6d97ce 100644
> --- a/hw/i386/pc_q35.c
> +++ b/hw/i386/pc_q35.c
> @@ -44,6 +44,7 @@
> #include "hw/ide/ahci.h"
> #include "hw/usb.h"
> #include "hw/cpu/icc_bus.h"
> +#include "qemu/error-report.h"
>
> /* ICH9 AHCI has 6 ports */
> #define MAX_SATA_PORTS 6
> @@ -85,6 +86,7 @@ static void pc_q35_init(MachineState *machine)
> PCIDevice *ahci;
> DeviceState *icc_bridge;
> PcGuestInfo *guest_info;
> + ram_addr_t lowmem;
>
> /* Check whether RAM fits below 4G (leaving 1/2 GByte for IO memory
> * and 256 Mbytes for PCI Express Enhanced Configuration Access Mapping
> @@ -96,7 +98,25 @@ static void pc_q35_init(MachineState *machine)
> * breaking migration.
> */
> if (machine->ram_size >= 0xb0000000) {
> - ram_addr_t lowmem = gigabyte_align ? 0x80000000 : 0xb0000000;
> + lowmem = gigabyte_align ? 0x80000000 : 0xb0000000;
> + } else {
> + lowmem = 0xb0000000;
> + }
> +
> + /* Handle the machine opt max-ram-below-4g. It is basicly doing
> + * min(qemu limit, user limit).
> + */
> + if (lowmem > pc_machine->max_ram_below_4g) {
> + lowmem = pc_machine->max_ram_below_4g;
> + if (machine->ram_size - lowmem > lowmem &&
> + lowmem & ((1ULL << 30) - 1)) {
> + error_report("Warning: Large machine and
> max_ram_below_4g(%"PRIu64
> + ") not a multiple of 1G; possible bad performance.",
> + pc_machine->max_ram_below_4g);
> + }
> + }
> +
> + if (machine->ram_size >= lowmem) {
> above_4g_mem_size = machine->ram_size - lowmem;
> below_4g_mem_size = lowmem;
> } else {
> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> index 76d4c6e..f5672ee 100644
> --- a/include/hw/i386/pc.h
> +++ b/include/hw/i386/pc.h
> @@ -33,10 +33,13 @@ 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 1617013..27c60eb 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -381,6 +381,10 @@ 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