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hw/arm/virt: Add 'compact-highmem' property

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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. The configuration is only achievable by
modifying the source code until more properties are added to allow
users selectively disable those high memory regions.

  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
  ----------------------------------------------------------------
  MEM                [1GB         512GB]        [1GB         512GB]
  HIGH_GIC_REDISTS2  [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 machine, 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>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Tested-by: Zhenyu Zhang <zhenyzha@redhat.com>
Message-id: 20221029224307.138822-7-gshan@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Gavin Shan 2022-12-14 14:27:06 +00:00 • committed by Peter Maydell
parent 4a4ff9edc6
commit f40408a9fe
3 changed files with 37 additions and 0 deletions
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4
docs/system/arm/virt.rst
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@ -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 the compact layout 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: