On Fri, 13 Jan 2023 22:01:08 +0000 Kechen Lu <kechenl@xxxxxxxxxx> wrote: Hi: checkpatch.pl throws a lot of warning and errors when I was trying this series. Can you fix them? total: 470 errors, 22 warnings, 464 lines checked > Summary > =========== > Introduce support of vCPU-scoped ioctl with KVM_CAP_X86_DISABLE_EXITS > cap for disabling exits to enable finer-grained VM exits disabling > on per vCPU scales instead of whole guest. This patch series enabled > the vCPU-scoped exits control and toggling. > > Motivation > ============ > In use cases like Windows guest running heavy CPU-bound > workloads, disabling HLT VM-exits could mitigate host sched ctx switch > overhead. Simply HLT disabling on all vCPUs could bring > performance benefits, but if no pCPUs reserved for host threads, could > happened to the forced preemption as host does not know the time to do > the schedule for other host threads want to run. With this patch, we > could only disable part of vCPUs HLT exits for one guest, this still > keeps performance benefits, and also shows resiliency to host stressing > workload running at the same time. > > Performance and Testing > ========================= > In the host stressing workload experiment with Windows guest heavy > CPU-bound workloads, it shows good resiliency and having the ~3% > performance improvement. E.g. Passmark running in a Windows guest > with this patch disabling HLT exits on only half of vCPUs still > showing 2.4% higher main score v/s baseline. > > Tested everything on AMD machines. > > v4->v5 : > - Drop the usage of KVM request, keep the VM-scoped exits disable > as the existing design, and only allow per-vCPU settings to > override the per-VM settings (Sean Christopherson) > - Refactor the disable exits selftest without introducing any > new prerequisite patch, tests per-vCPU exits disable and overrides, > and per-VM exits disable > > v3->v4 (Chao Gao) : > - Use kvm vCPU request KVM_REQ_DISABLE_EXIT to perform the arch > VMCS updating (patch 5) > - Fix selftests redundant arguments (patch 7) > - Merge overlapped fix bits from patch 4 to patch 3 > > v2->v3 (Sean Christopherson) : > - Reject KVM_CAP_X86_DISABLE_EXITS if userspace disable MWAIT exits > when MWAIT is not allowed in guest (patch 3) > - Make userspace able to re-enable previously disabled exits (patch 4) > - Add mwait/pause/cstate exits flag toggling instead of only hlt > exits (patch 5) > - Add selftests for KVM_CAP_X86_DISABLE_EXITS (patch 7) > > v1->v2 (Sean Christopherson) : > - Add explicit restriction for VM-scoped exits disabling to be called > before vCPUs creation (patch 1) > - Use vCPU ioctl instead of 64bit vCPU bitmask (patch 5), and make exits > disable flags check purely for vCPU instead of VM (patch 2) > > Best Regards, > Kechen > > Kechen Lu (3): > KVM: x86: Move *_in_guest power management flags to vCPU scope > KVM: x86: add vCPU scoped toggling for disabled exits > KVM: selftests: Add tests for VM and vCPU cap > KVM_CAP_X86_DISABLE_EXITS > > Sean Christopherson (3): > KVM: x86: only allow exits disable before vCPUs created > KVM: x86: Reject disabling of MWAIT interception when not allowed > KVM: x86: Let userspace re-enable previously disabled exits > > Documentation/virt/kvm/api.rst | 8 +- > arch/x86/include/asm/kvm-x86-ops.h | 1 + > arch/x86/include/asm/kvm_host.h | 7 + > arch/x86/kvm/cpuid.c | 4 +- > arch/x86/kvm/lapic.c | 7 +- > arch/x86/kvm/svm/nested.c | 4 +- > arch/x86/kvm/svm/svm.c | 42 +- > arch/x86/kvm/vmx/vmx.c | 53 +- > arch/x86/kvm/x86.c | 69 ++- > arch/x86/kvm/x86.h | 16 +- > include/uapi/linux/kvm.h | 4 +- > tools/testing/selftests/kvm/Makefile | 1 + > .../selftests/kvm/x86_64/disable_exits_test.c | 457 ++++++++++++++++++ > 13 files changed, 626 insertions(+), 47 deletions(-) > create mode 100644 tools/testing/selftests/kvm/x86_64/disable_exits_test.c >
