On Wed, Oct 12 2022, Gavin Shan <gs...@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; > > # 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 <gs...@redhat.com> > Tested-by: Zhenyu Zhang <zheny...@redhat.com> > --- > docs/system/arm/virt.rst | 4 ++++ > hw/arm/virt.c | 47 ++++++++++++++++++++++++++++++++++++++++ > include/hw/arm/virt.h | 1 + > 3 files changed, 52 insertions(+) > > 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.
Maybe s/compact space/the compact layout/ ? > + 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 c05cfb5314..8f1dba0ece 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 s/space in/layout for/ ? > + * 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) > */ (...) > @@ -3124,8 +3167,12 @@ 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 */ s/space/layout/ ? > + vmc->no_highmem_compact = true; > } > DEFINE_VIRT_MACHINE(7, 1) > Other than the wording nits, lgtm. Reviewed-by: Cornelia Huck <coh...@redhat.com>