VMX: Support for coexistence of KVM and other hosted VMMs. The following NOTE is picked up from Intel SDM 3B 27.3 chapter, MANAGING VMCS REGIONS AND POINTERS.
---------------------- NOTE As noted in Section 21.1, the processor may optimize VMX operation by maintaining the state of an active VMCS (one for which VMPTRLD has been executed) on the processor. Before relinquishing control to other system software that may, without informing the VMM, remove power from the processor (e.g., for transitions to S3 or S4) or leave VMX operation, a VMM must VMCLEAR all active VMCSs. This ensures that all VMCS data cached by the processor are flushed to memory and that no other software can corrupt the current VMM's VMCS data. It is also recommended that the VMM execute VMXOFF after such executions of VMCLEAR. ---------------------- Currently, VMCLEAR is called at VCPU migration. To support hosted VMM coexistence, this patch modifies the VMCLEAR/VMPTRLD and VMXON/VMXOFF usages. VMCLEAR will be called when VCPU is scheduled out of a physical CPU, while VMPTRLD is called when VCPU is scheduled in a physical CPU. Also this approach could eliminates the IPI mechanism for original VMCLEAR. As suggested by SDM, VMXOFF will be called after VMCLEAR, and VMXON will be called before VMPTRLD. With this patchset, KVM and VMware Workstation 7 could launch serapate guests and they can work well with each other. Besides, I measured the performance for this patch, there is no visable performance loss according to the test results. The following performance results are got from a host with 8 cores. 1. vConsolidate benchmarks on KVM Test Round WebBench SPECjbb SysBench LoadSim GEOMEAN 1 W/O patch 2,614.72 28,053.09 1,108.41 16.30 1,072.95 W/ patch 2,691.55 28,145.71 1,128.41 16.47 1,089.28 2 W/O patch 2,642.39 28,104.79 1,096.99 17.79 1,097.19 W/ patch 2,699.25 28,092.62 1,116.10 15.54 1,070.98 3 W/O patch 2,571.58 28,131.17 1,108.43 16.39 1,070.70 W/ patch 2,627.89 28,090.19 1,110.94 17.00 1,086.57 Average W/O patch 2,609.56 28,096.35 1,104.61 16.83 1,080.28 W/ patch 2,672.90 28,109.51 1,118.48 16.34 1,082.28 2. CPU overcommitment tests for KVM A) Run 8 while(1) in host which pin with 8 cores. B) Launch 6 guests, each has 8 VCPUs, pin each VCPU with one core. C) Among the 6 guests, 5 of them are running 8*while(1). D) The left guest is doing kernel build "make -j9" under ramdisk. In this case, the overcommitment ratio for each core is 7:1. The VCPU schedule frequency on all cores is totally ~15k/sec. l record the kernel build time. While doing the average, the first round data is treated as invalid, which isn't counted into the final average result. Kernel Build Time (second) Round w/o patch w/ patch 1 541 501 2 488 490 3 488 492 4 492 493 5 489 491 6 494 487 7 497 494 8 492 492 9 493 496 10 492 495 11 490 496 12 489 494 13 489 490 14 490 491 15 494 497 16 495 496 17 496 496 18 493 492 19 493 500 20 490 499 Average 491.79 493.74 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
