From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43244) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wu50h-00013a-Bb for qemu-devel@nongnu.org; Mon, 09 Jun 2014 15:13:40 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Wu50c-0006St-0d for qemu-devel@nongnu.org; Mon, 09 Jun 2014 15:13:35 -0400 Received: from fldsmtpe04.verizon.com ([140.108.26.143]:42853) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wu50b-0006Si-OO for qemu-devel@nongnu.org; Mon, 09 Jun 2014 15:13:29 -0400 From: Don Slutz Message-ID: <53960750.3050300@terremark.com> Date: Mon, 09 Jun 2014 15:13:20 -0400 MIME-Version: 1.0 References: <1402077126-17799-1-git-send-email-dslutz@verizon.com> <1402077126-17799-3-git-send-email-dslutz@verizon.com> <20140608154014.GE8464@redhat.com> <5395C2C9.7070200@terremark.com> <20140609143844.GA6797@redhat.com> In-Reply-To: <20140609143844.GA6797@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v5 2/3] pc & q35: Add new machine opt max-ram-below-4g List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" , Don Slutz , Gerd Hoffmann Cc: xen-devel@lists.xensource.com, Stefano Stabellini , qemu-devel@nongnu.org, Anthony Liguori , Igor Mammedov , =?ISO-8859-1?Q?Andreas_F=E4rber?= On 06/09/14 10:38, 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 >>>> --- >>>> 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 :) > Sigh, will fix. >>>> + 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); >>>> } >>>> 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) { >>> 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. You are right. And I also found: static void pc_init1(MachineState *machine, int pci_enabled, int kvmclock_enabled) { PCMachineState *pc_machine = PC_MACHINE(machine); ... PCMachineState *pcms = PC_MACHINE(mo); ... and so I will drop the add of pcms. >>>> + 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. > I do not see a way to encode the default since for QEMU 2.0 it depends on the specified ram size: > This is intentional. > If we can fit all ram into low memory, because it is less than 3.5G, > we'll do that (pc machine type, q35 numbers are different but logic is > the same). This way 32bit (+non-PAE) guests can continue to have up to > 3.5G memory. > If we can't fit all ram into low memory (thus the guest should be able > to access ram above 4G anyway), then we'll cut off at a gigabyte > boundary (3G for pc machine type). This way our ram is nicely > gigabyte-aligned and we can get best performance benefits from huge > pages. > The size of the pci hole changing in the second case is only a side > effect, it's not the main reason for the change. > cheers, > Gerd So migration of a QEMU 2.0 pc to QEMU 2.1 without gigabyte_align would require the user to specify the correct value of max-ram-below-4g. When you add xen into the mix I do not see a way to get right of gigabyte_align. You have 3 cases: 1) old xen (without max-ram-below-4g), QEMU 2.1 or later. Will expect that QEMU acts as if max-ram-below-4g=3.75G was specified. I.E. gigabyte_align is ignored. Note: xen 4.4 asks for "pc,accel=xen" in some cases. 2) new xen (with max-ram-below-4g), QEMU 2.0 or earlier. Will expect that QEMU acts as if max-ram-below-4g=3.75G was specified. If any other value requested, the error from QEMU is ok. 3) new xen (with max-ram-below-4g), QEMU 2.1 or later. Expects that max-ram-below-4g works. In summary, the migration of QEMU pc-i440fx-2.0 and pc-q35-2.0 guests for accel=tcg, accel=kvm, accel=xen needs the gigabyte_align mess. -Don Slutz > >>> 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 From mboxrd@z Thu Jan 1 00:00:00 1970 From: Don Slutz Subject: Re: [PATCH v5 2/3] pc & q35: Add new machine opt max-ram-below-4g Date: Mon, 09 Jun 2014 15:13:20 -0400 Message-ID: <53960750.3050300@terremark.com> References: <1402077126-17799-1-git-send-email-dslutz@verizon.com> <1402077126-17799-3-git-send-email-dslutz@verizon.com> <20140608154014.GE8464@redhat.com> <5395C2C9.7070200@terremark.com> <20140609143844.GA6797@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140609143844.GA6797@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org Sender: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org To: "Michael S. Tsirkin" , Don Slutz , Gerd Hoffmann Cc: xen-devel@lists.xensource.com, Stefano Stabellini , qemu-devel@nongnu.org, Anthony Liguori , Igor Mammedov , =?ISO-8859-1?Q?Andreas_F=E4rber?= List-Id: xen-devel@lists.xenproject.org On 06/09/14 10:38, 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 >>>> --- >>>> 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 :) > Sigh, will fix. >>>> + 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); >>>> } >>>> 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) { >>> 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. You are right. And I also found: static void pc_init1(MachineState *machine, int pci_enabled, int kvmclock_enabled) { PCMachineState *pc_machine = PC_MACHINE(machine); ... PCMachineState *pcms = PC_MACHINE(mo); ... and so I will drop the add of pcms. >>>> + 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. > I do not see a way to encode the default since for QEMU 2.0 it depends on the specified ram size: > This is intentional. > If we can fit all ram into low memory, because it is less than 3.5G, > we'll do that (pc machine type, q35 numbers are different but logic is > the same). This way 32bit (+non-PAE) guests can continue to have up to > 3.5G memory. > If we can't fit all ram into low memory (thus the guest should be able > to access ram above 4G anyway), then we'll cut off at a gigabyte > boundary (3G for pc machine type). This way our ram is nicely > gigabyte-aligned and we can get best performance benefits from huge > pages. > The size of the pci hole changing in the second case is only a side > effect, it's not the main reason for the change. > cheers, > Gerd So migration of a QEMU 2.0 pc to QEMU 2.1 without gigabyte_align would require the user to specify the correct value of max-ram-below-4g. When you add xen into the mix I do not see a way to get right of gigabyte_align. You have 3 cases: 1) old xen (without max-ram-below-4g), QEMU 2.1 or later. Will expect that QEMU acts as if max-ram-below-4g=3.75G was specified. I.E. gigabyte_align is ignored. Note: xen 4.4 asks for "pc,accel=xen" in some cases. 2) new xen (with max-ram-below-4g), QEMU 2.0 or earlier. Will expect that QEMU acts as if max-ram-below-4g=3.75G was specified. If any other value requested, the error from QEMU is ok. 3) new xen (with max-ram-below-4g), QEMU 2.1 or later. Expects that max-ram-below-4g works. In summary, the migration of QEMU pc-i440fx-2.0 and pc-q35-2.0 guests for accel=tcg, accel=kvm, accel=xen needs the gigabyte_align mess. -Don Slutz > >>> 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