UMONITOR, UMWAIT and TPAUSE are a set of user wait instructions.
Availability of the user wait instructions is indicated by the presence
of the CPUID feature flag WAITPKG CPUID.0x07.0x0:ECX[5].
The patch 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
Co-developed-by: Jingqi Liu <address@hidden>
Signed-off-by: Jingqi Liu <address@hidden>
Signed-off-by: Tao Xu <address@hidden>
---
linux-headers/linux/kvm.h | 1 +
target/i386/cpu.c | 3 ++-
target/i386/cpu.h | 1 +
target/i386/kvm.c | 13 +++++++++++++
4 files changed, 17 insertions(+), 1 deletion(-)
diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
index c8423e760c..86cc2dbdd0 100644
--- a/linux-headers/linux/kvm.h
+++ b/linux-headers/linux/kvm.h
@@ -993,6 +993,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_ARM_SVE 170
#define KVM_CAP_ARM_PTRAUTH_ADDRESS 171
#define KVM_CAP_ARM_PTRAUTH_GENERIC 172
+#define KVM_CAP_ENABLE_USR_WAIT_PAUSE 173
#ifdef KVM_CAP_IRQ_ROUTING