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.
/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
Thanks,
Gavin
