On 11/10/19 09:41, Tao Xu wrote: > UMONITOR, UMWAIT and TPAUSE are a set of user wait instructions. > > UMONITOR arms address monitoring hardware using an address. A store > to an address within the specified address range triggers the > monitoring hardware to wake up the processor waiting in umwait. > > UMWAIT instructs the processor to enter an implementation-dependent > optimized state while monitoring a range of addresses. The optimized > state may be either a light-weight power/performance optimized state > (c0.1 state) or an improved power/performance optimized state > (c0.2 state). > > TPAUSE instructs the processor to enter an implementation-dependent > optimized state c0.1 or c0.2 state and wake up when time-stamp counter > reaches specified timeout. > > Availability of the user wait instructions is indicated by the presence > of the CPUID feature flag WAITPKG CPUID.0x07.0x0:ECX[5]. > > The patches enable the umonitor, umwait and tpause features in KVM. > Because umwait and tpause can put a (psysical) CPU into a power saving > state, by default we dont't expose it in kvm and provide a capability to > enable it. Use kvm capability to enable UMONITOR, UMWAIT and TPAUSE when > QEMU use "-overcommit cpu-pm=on, a VM can use UMONITOR, UMWAIT and TPAUSE > instructions. If the instruction causes a delay, the amount of time > delayed is called here the physical delay. The physical delay is first > computed by determining the virtual delay (the time to delay relative to > the VM’s timestamp counter). Otherwise, UMONITOR, UMWAIT and TPAUSE cause > an invalid-opcode exception(#UD). > > The release document ref below link: > https://software.intel.com/sites/default/files/\ > managed/39/c5/325462-sdm-vol-1-2abcd-3abcd.pdf > > Changelog: > v6: > Remove CPUID_7_0_ECX_WAITPKG if enable_cpu_pm is not set. > (Paolo) > > Tao Xu (2): > x86/cpu: Add support for UMONITOR/UMWAIT/TPAUSE > target/i386: Add support for save/load IA32_UMWAIT_CONTROL MSR > > target/i386/cpu.c | 2 +- > target/i386/cpu.h | 3 +++ > target/i386/kvm.c | 19 +++++++++++++++++++ > target/i386/machine.c | 20 ++++++++++++++++++++ > 4 files changed, 43 insertions(+), 1 deletion(-) > Queued, thanks. Paolo
