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[PATCH 0/1] hw/arm/virt: Support for virtio-mem-pci

From: Gavin Shan
Subject: [PATCH 0/1] hw/arm/virt: Support for virtio-mem-pci
Date: Tue, 30 Nov 2021 08:33:27 +0800

This series supports virtio-mem-pci device, by simply following the
implementation on x86. The exception is the block size is 1GB on ARM64
instead of 128MB on x86.

The work was done by David Hildenbrand and then Jonathan Cameron. I'm
taking the patch and putting more efforts, which is all about testing
to me at current stage.


The upstream linux kernel (v5.16.rc3) is used on host/guest during
the testing. The guest kernel includes changes to enable virtio-mem
driver, which is simply to enable CONFIG_VIRTIO_MEM on ARM64.

Mutiple combinations like page sizes on host/guest, memory backend
device etc are covered in the testing. Besides, migration is also
tested. The following command lines are used for VM or virtio-mem-pci
device hot-add. It's notable that virtio-mem-pci device hot-remove
isn't supported, similar to what we have on x86. 

  host.pgsize  guest.pgsize  backend    hot-add  hot-remove  migration
   4KB         4KB           normal     ok       ok          ok
                             THP        ok       ok          ok
                             hugeTLB    ok       ok          ok
   4KB         64KB          normal     ok       ok          ok
                             THP        ok       ok          ok
                             hugeTLB    ok       ok          ok
  64KB         4KB           normal     ok       ok          ok
                             THP        ok       ok          ok
                             hugeTLB    ok       ok          ok
  64KB         64KB          normal     ok       ok          ok
                             THP        ok       ok          ok
                             hugeTLB    ok       ok          ok

The command lines are used for VM. When hugeTLBfs is used, all memory
backend objects are popuated on /dev/hugepages-2048kB or
/dev/hugepages-524288kB, depending on the host page sizes.

  -accel kvm -machine virt,gic-version=host                                     
  -cpu host -smp 4,sockets=2,cores=2,threads=1                                  
  -m 1024M,slots=16,maxmem=64G                                                  
  -object memory-backend-ram,id=mem0,size=512M                                  
  -object memory-backend-ram,id=mem1,size=512M                                  
  -numa node,nodeid=0,cpus=0-1,memdev=mem0                                      
  -numa node,nodeid=1,cpus=2-3,memdev=mem1                                      
  -kernel /home/gavin/sandbox/linux.guest/arch/arm64/boot/Image                 
  -initrd /home/gavin/sandbox/images/rootfs.cpio.xz                             
  -append earlycon=pl011,mmio,0x9000000                                         
  -device pcie-root-port,bus=pcie.0,chassis=1,id=pcie.1                         
  -device pcie-root-port,bus=pcie.0,chassis=2,id=pcie.2                         
  -device pcie-root-port,bus=pcie.0,chassis=3,id=pcie.3                         
  -object memory-backend-ram,id=vmem0,size=512M                                 
  -device virtio-mem-pci,id=vm0,bus=pcie.1,memdev=vmem0,node=0,requested-size=0 
  -object memory-backend-ram,id=vmem1,size=512M                                 
  -device virtio-mem-pci,id=vm1,bus=pcie.2,memdev=vmem1,node=1,requested-size=0 

Command lines used for memory hot-add and hot-remove:

  (qemu) qom-set vm1 requested-size 512M
  (qemu) qom-set vm1 requested-size 0
  (qemu) qom-set vm1 requested-size 512M

Command lines used for virtio-mem-pci device hot-add:

  (qemu) object_add memory-backend-ram,id=hp-mem1,size=512M
  (qemu) device_add virtio-mem-pci,id=hp-vm1,bus=pcie.3,memdev=hp-mem1,node=1
  (qemu) qom-set hp-vm1 requested-size 512M
  (qemu) qom-set hp-vm1 requested-size 0
  (qemu) qom-set hp-vm1 requested-size 512M

Gavin Shan (1):
  hw/arm/virt: Support for virtio-mem-pci

 hw/arm/Kconfig         |  1 +
 hw/arm/virt.c          | 68 +++++++++++++++++++++++++++++++++++++++++-
 hw/virtio/virtio-mem.c |  2 ++
 3 files changed, 70 insertions(+), 1 deletion(-)


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