2017-10-23 17:44-0700, Eduardo Valentin: > Currently, the existing qspinlock implementation will fallback to > test-and-set if the hypervisor has not set the PV_UNHALT flag. Where have you detected the main source of overhead with pinned VCPUs? Makes me wonder if we couldn't improve general PV_UNHALT, thanks. > This patch gives the opportunity to guest kernels to select > between test-and-set and the regular queueu fair lock implementation > based on the PV_DEDICATED KVM feature flag. When the PV_DEDICATED > flag is not set, the code will still fall back to test-and-set, > but when the PV_DEDICATED flag is set, the code will use > the regular queue spinlock implementation. Some flag makes sense and we do want to make sure that userspaces don't enable it in pass-through-cpuid mode.
