This series implements guest time scaling based on RDTIME instruction emulation so that we can allow migrating Guest/VM across Hosts with different time frequency. Why not through para-virt. From arm's experience[1], para-virt implementation doesn't really solve the problem for the following two main reasons: - RDTIME not only be used in linux, but also in firmware and userspace. - It is difficult to be compatible with nested virtualization. [1] https://lore.kernel.org/patchwork/cover/1288153/ Yifei Jiang (3): RISC-V: KVM: Change the method of calculating cycles to nanoseconds RISC-V: KVM: Support dynamic time frequency from userspace RISC-V: KVM: Implement guest time scaling arch/riscv/include/asm/csr.h | 3 ++ arch/riscv/include/asm/kvm_vcpu_timer.h | 13 +++++-- arch/riscv/kvm/vcpu_exit.c | 35 +++++++++++++++++ arch/riscv/kvm/vcpu_timer.c | 51 ++++++++++++++++++++++--- 4 files changed, 93 insertions(+), 9 deletions(-) -- 2.19.1
