| Message ID | 20221004002627.59172-7-gshan@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | hw/arm/virt: Improve address assignment for high memory regions | expand |
On Tue, 04 Oct 2022 01:26:27 +0100, Gavin Shan <gshan@redhat.com> wrote: > > After the improvement to high memory region address assignment is > applied, the memory layout can be changed, introducing possible > migration breakage. For example, VIRT_HIGH_PCIE_MMIO memory region > is disabled or enabled when the optimization is applied or not, with > the following configuration. > > pa_bits = 40; > vms->highmem_redists = false; > vms->highmem_ecam = false; > vms->highmem_mmio = true; The question is how are these parameters specified by a user? Short of hacking the code, this isn't really possible. > > # qemu-system-aarch64 -accel kvm -cpu host \ > -machine virt-7.2,compact-highmem={on, off} \ > -m 4G,maxmem=511G -monitor stdio > > Region compact-highmem=off compact-highmem=on > ---------------------------------------------------------------- > RAM [1GB 512GB] [1GB 512GB] > HIGH_GIC_REDISTS [512GB 512GB+64MB] [disabled] > HIGH_PCIE_ECAM [512GB+256MB 512GB+512MB] [disabled] > HIGH_PCIE_MMIO [disabled] [512GB 1TB] > > In order to keep backwords compatibility, we need to disable the > optimization on machines, which is virt-7.1 or ealier than it. It > means the optimization is enabled by default from virt-7.2. Besides, > 'compact-highmem' property is added so that the optimization can be > explicitly enabled or disabled on all machine types by users. Not directly related to this series, but it seems to me that we should be aiming at reproducible results across HW implementations (at least with KVM). Depending on how many PA bits the HW implements, we end-up with a set of devices or another, which is likely to be confusing for a user. I think we should consider an additional set of changes to allow a user to specify the PA bits as well as the devices they want to see enabled. Thanks, M.
Hi Marc, On 10/5/22 1:39 AM, Marc Zyngier wrote: > On Tue, 04 Oct 2022 01:26:27 +0100, > Gavin Shan <gshan@redhat.com> wrote: >> >> After the improvement to high memory region address assignment is >> applied, the memory layout can be changed, introducing possible >> migration breakage. For example, VIRT_HIGH_PCIE_MMIO memory region >> is disabled or enabled when the optimization is applied or not, with >> the following configuration. >> >> pa_bits = 40; >> vms->highmem_redists = false; >> vms->highmem_ecam = false; >> vms->highmem_mmio = true; > > The question is how are these parameters specified by a user? Short of > hacking the code, this isn't really possible. > Yeah, It's impossible to have false for vms->highmem_redists unless the code is hacked. >> >> # qemu-system-aarch64 -accel kvm -cpu host \ >> -machine virt-7.2,compact-highmem={on, off} \ >> -m 4G,maxmem=511G -monitor stdio >> >> Region compact-highmem=off compact-highmem=on >> ---------------------------------------------------------------- >> RAM [1GB 512GB] [1GB 512GB] >> HIGH_GIC_REDISTS [512GB 512GB+64MB] [disabled] >> HIGH_PCIE_ECAM [512GB+256MB 512GB+512MB] [disabled] >> HIGH_PCIE_MMIO [disabled] [512GB 1TB] >> >> In order to keep backwords compatibility, we need to disable the >> optimization on machines, which is virt-7.1 or ealier than it. It >> means the optimization is enabled by default from virt-7.2. Besides, >> 'compact-highmem' property is added so that the optimization can be >> explicitly enabled or disabled on all machine types by users. > > Not directly related to this series, but it seems to me that we should > be aiming at reproducible results across HW implementations (at least > with KVM). Depending on how many PA bits the HW implements, we end-up > with a set of devices or another, which is likely to be confusing for > a user. > > I think we should consider an additional set of changes to allow a > user to specify the PA bits as well as the devices they want to see > enabled. > I think the idea to selectively enable devices (high memory regions) is sensible. For example, users may needn't HIGH_PCIE_MMIO at all in some systems, where they have limited PCI devices. I'm not sure about PA bits because it has been discovered from hardware and configure the automatically optimized value/bits back to KVM. The optimized value/bits is automatically calculated based on the enabled high memory regions. Thanks, Gavin
diff --git a/docs/system/arm/virt.rst b/docs/system/arm/virt.rst index 20442ea2c1..75bf5a4994 100644 --- a/docs/system/arm/virt.rst +++ b/docs/system/arm/virt.rst @@ -94,6 +94,10 @@ highmem address space above 32 bits. The default is ``on`` for machine types later than ``virt-2.12``. +compact-highmem + Set ``on``/``off`` to enable/disable compact space for high memory regions. + The default is ``on`` for machine types later than ``virt-7.2`` + gic-version Specify the version of the Generic Interrupt Controller (GIC) to provide. Valid values are: diff --git a/hw/arm/virt.c b/hw/arm/virt.c index 4164da49e9..9fe65a2ae1 100644 --- a/hw/arm/virt.c +++ b/hw/arm/virt.c @@ -174,6 +174,27 @@ static const MemMapEntry base_memmap[] = { * Note the extended_memmap is sized so that it eventually also includes the * base_memmap entries (VIRT_HIGH_GIC_REDIST2 index is greater than the last * index of base_memmap). + * + * The addresses assigned to these regions are affected by 'compact-highmem' + * property, which is to enable or disable the compact space in the Highmem + * IO regions. For example, VIRT_HIGH_PCIE_MMIO can be disabled or enabled + * depending on the property in the following scenario. + * + * pa_bits = 40; + * vms->highmem_redists = false; + * vms->highmem_ecam = false; + * vms->highmem_mmio = true; + * + * # qemu-system-aarch64 -accel kvm -cpu host \ + * -machine virt-7.2,compact-highmem={on, off} \ + * -m 4G,maxmem=511G -monitor stdio + * + * Region compact-highmem=off compact-highmem=on + * ---------------------------------------------------------------- + * RAM [1GB 512GB] [1GB 512GB] + * HIGH_GIC_REDISTS [512GB 512GB+64MB] [disabled] + * HIGH_PCIE_ECAM [512GB+256GB 512GB+512MB] [disabled] + * HIGH_PCIE_MMIO [disabled] [512GB 1TB] */ static MemMapEntry extended_memmap[] = { /* Additional 64 MB redist region (can contain up to 512 redistributors) */ @@ -2349,6 +2370,20 @@ static void virt_set_highmem(Object *obj, bool value, Error **errp) vms->highmem = value; } +static bool virt_get_compact_highmem(Object *obj, Error **errp) +{ + VirtMachineState *vms = VIRT_MACHINE(obj); + + return vms->highmem_compact; +} + +static void virt_set_compact_highmem(Object *obj, bool value, Error **errp) +{ + VirtMachineState *vms = VIRT_MACHINE(obj); + + vms->highmem_compact = value; +} + static bool virt_get_its(Object *obj, Error **errp) { VirtMachineState *vms = VIRT_MACHINE(obj); @@ -2967,6 +3002,13 @@ static void virt_machine_class_init(ObjectClass *oc, void *data) "Set on/off to enable/disable using " "physical address space above 32 bits"); + object_class_property_add_bool(oc, "compact-highmem", + virt_get_compact_highmem, + virt_set_compact_highmem); + object_class_property_set_description(oc, "compact-highmem", + "Set on/off to enable/disable compact " + "space for high memory regions"); + object_class_property_add_str(oc, "gic-version", virt_get_gic_version, virt_set_gic_version); object_class_property_set_description(oc, "gic-version", @@ -3051,6 +3093,7 @@ static void virt_instance_init(Object *obj) /* High memory is enabled by default */ vms->highmem = true; + vms->highmem_compact = !vmc->no_highmem_compact; vms->gic_version = VIRT_GIC_VERSION_NOSEL; vms->highmem_ecam = !vmc->no_highmem_ecam; @@ -3120,8 +3163,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(7, 2) static void virt_machine_7_1_options(MachineClass *mc) { + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc)); + virt_machine_7_2_options(mc); compat_props_add(mc->compat_props, hw_compat_7_1, hw_compat_7_1_len); + /* Compact space for high memory regions was introduced with 7.2 */ + vmc->no_highmem_compact = true; } DEFINE_VIRT_MACHINE(7, 1) diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h index 709f623741..c7dd59d7f1 100644 --- a/include/hw/arm/virt.h +++ b/include/hw/arm/virt.h @@ -125,6 +125,7 @@ struct VirtMachineClass { bool no_pmu; bool claim_edge_triggered_timers; bool smbios_old_sys_ver; + bool no_highmem_compact; bool no_highmem_ecam; bool no_ged; /* Machines < 4.2 have no support for ACPI GED device */ bool kvm_no_adjvtime;
After the improvement to high memory region address assignment is applied, the memory layout can be changed, introducing possible migration breakage. For example, VIRT_HIGH_PCIE_MMIO memory region is disabled or enabled when the optimization is applied or not, with the following configuration. pa_bits = 40; vms->highmem_redists = false; vms->highmem_ecam = false; vms->highmem_mmio = true; # qemu-system-aarch64 -accel kvm -cpu host \ -machine virt-7.2,compact-highmem={on, off} \ -m 4G,maxmem=511G -monitor stdio Region compact-highmem=off compact-highmem=on ---------------------------------------------------------------- RAM [1GB 512GB] [1GB 512GB] HIGH_GIC_REDISTS [512GB 512GB+64MB] [disabled] HIGH_PCIE_ECAM [512GB+256MB 512GB+512MB] [disabled] HIGH_PCIE_MMIO [disabled] [512GB 1TB] In order to keep backwords compatibility, we need to disable the optimization on machines, which is virt-7.1 or ealier than it. It means the optimization is enabled by default from virt-7.2. Besides, 'compact-highmem' property is added so that the optimization can be explicitly enabled or disabled on all machine types by users. Signed-off-by: Gavin Shan <gshan@redhat.com> --- docs/system/arm/virt.rst | 4 ++++ hw/arm/virt.c | 47 ++++++++++++++++++++++++++++++++++++++++ include/hw/arm/virt.h | 1 + 3 files changed, 52 insertions(+)