On 04/06/2016 02:24, yunhong jiang wrote: >> > 2) if possible, I would like to remove kvm_lapic_arm_hv_timer. >> > Instead, make switch_to_hv_lapic_timer and start_apic_timer can call >> > kvm_x86_ops->set_hv_timer, passing the desired *guest* TSC. >> > set_hv_timer can convert the guest TSC to a host TSC and save the >> > desired host TSC in struct vmx_vcpu. vcpu_run checks if there is a > Hi, Paolo, I mostly finished my patch, but one thing come to my mind in > the last minutes and hope to get your input. > One issue to save the host TSC on the vmx_vcpu is, if the vCPU thread > is migrated to another pCPU, and the TSC are not synchronized between > these two pCPUs, then the result is not accurate. In previous patchset, > it's ok because we do the calculation on the vcpu_run() thus the > migration does not matter. My suggestion here is to redo the vmx_set_hv_timer in vmx_vcpu_load. It should fix the 32-bit overflow below, too. Paolo > This also bring a tricky situation considering the VMX preepmtion timer > can only hold 32bit value. In a rare situation, the host delta TSC is > less than 32 bit, however, if there is a host tsc backwards after the > migration, then the delta TSC on the new CPU may be larger than 32 bit, > but we can't switch back to sw timer anymore because it's too late. I > add some hacky code on the kvm_arch_vcpu_load(), not sure if it's ok. > > I will send a RFC patch. I'm still looking for a > platform with TSC scaling support, thus not test TSC scaling > yet. Others has been tested. > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
