Hi Gavin, > From: Gavin Shan <gs...@redhat.com> > Sent: Monday, August 19, 2024 6:32 AM > To: Salil Mehta <salil.me...@huawei.com>; qemu-devel@nongnu.org; > qemu-...@nongnu.org; m...@redhat.com > > On 6/14/24 9:36 AM, Salil Mehta wrote: > > In the ARMv8 architecture, the GIC must know all the CPUs it is > > connected to during its initialization, and this cannot change > > afterward. This must be ensured during the initialization of the VGIC > > as well in KVM, which requires all vCPUs to be created and present > > during its initialization. This is necessary > > because: > > > > 1. The association between GICC and MPIDR must be fixed at VM > initialization > > time. This is represented by the register `GIC_TYPER(mp_affinity, > proc_num)`. > > 2. GICC (CPU interfaces), GICR (redistributors), etc., must all be > initialized > > at boot time. > > 3. Memory regions associated with GICR, etc., cannot be changed (added, > deleted, > > or modified) after the VM has been initialized. > > > > This patch adds support to pre-create all possible vCPUs within the > > host using the KVM interface as part of the virtual machine > > initialization. These vCPUs can later be attached to QOM/ACPI when > > they are actually hot-plugged and made present. > > > > Co-developed-by: Keqian Zhu <zhukeqi...@huawei.com> > > Signed-off-by: Keqian Zhu <zhukeqi...@huawei.com> > > Signed-off-by: Salil Mehta <salil.me...@huawei.com> > > Reported-by: Vishnu Pajjuri <vis...@os.amperecomputing.com> > > [VP: Identified CPU stall issue & suggested probable fix] > > --- > > hw/arm/virt.c | 56 +++++++++++++++++++++++++++++++++++----- > --- > > include/hw/core/cpu.h | 1 + > > target/arm/cpu64.c | 1 + > > target/arm/kvm.c | 41 ++++++++++++++++++++++++++++++- > > target/arm/kvm_arm.h | 11 +++++++++ > > 5 files changed, 99 insertions(+), 11 deletions(-) > > > > The vCPU file descriptor is associated with a feature bitmap when the file > descriptor is initialized by ioctl(vm_fd, KVM_ARM_VCPU_INIT, &init). The > feature bitmap is sorted out based on the vCPU properties. The vCPU > properties can be different when the vCPU file descriptor is initialized for > the first time when the vCPU is instantiated, and re-initialized when the > vCPU is hot added.
> It can lead to system crash as below. We probably need a mechanism to > disallow passing extra properties when vCPU is hot added to avoid the > conflicts to the global properties from the command line "-cpu > host,pmu=on". Some of the properties like "id", "socket-id" > are still needed. Yes, Good catch. I knew that but It almost went under my hood. Thanks for pointing and reminding it. We need a check there. Will fix it. > > /home/gavin/sandbox/qemu.main/build/qemu-system-aarch64 \ > -accel kvm -machine virt,gic-version=host,nvdimm=on \ > -cpu host -smp maxcpus=2,cpus=1,sockets=2,clusters=1,cores=1,threads=1 > \ > -m 4096M,slots=16,maxmem=128G \ > -object memory-backend-ram,id=mem0,size=2048M \ > -object memory-backend-ram,id=mem1,size=2048M \ > -numa node,nodeid=0,memdev=mem0,cpus=0-0 \ > -numa node,nodeid=1,memdev=mem1,cpus=1-1 \ > -L /home/gavin/sandbox/qemu.main/build/pc-bios \ > -monitor none -serial mon:stdio -nographic \ > -gdb tcp::6666 -qmp tcp:localhost:5555,server,wait=off \ > -bios /home/gavin/sandbox/qemu.main/build/pc-bios/edk2-aarch64- > code.fd \ > -kernel /home/gavin/sandbox/linux.guest/arch/arm64/boot/Image \ > -initrd /home/gavin/sandbox/images/rootfs.cpio.xz \ > -append memhp_default_state=online_movable \ > : > (qemu) device_add host-arm-cpu,id=cpu1,socket-id=1,pmu=off > kvm_arch_init_vcpu: Error -22 from kvm_arm_vcpu_init() > qemu-system-aarch64: kvm_init_vcpu: kvm_arch_init_vcpu failed (1): > Invalid argument Yes. thanks. > > Thanks, > Gavin >
