KVM: arm64: Add SMCCC PV-sched to kick cpu

euleros inclusion
category: feature
bugzilla: NA
CVE: NA

--------------------------------

A new hypercall interface function is provided for the guest to kick WFI
state vCPU.
Signed-off-by: NZengruan Ye <yezengruan@huawei.com>
Reviewed-by: Nzhanghailiang <zhang.zhanghailiang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

Documentation/virtual/kvm/arm/pvsched.txt

@@ -9,6 +9,7 @@ Some SMCCC compatible hypercalls are defined:
 * PV_SCHED_FEATURES:          0xC5000090
 * PV_SCHED_IPA_INIT:          0xC5000091
 * PV_SCHED_IPA_RELEASE:       0xC5000092
+* PV_SCHED_KICK_CPU:          0xC5000093
 
 The existence of the PV_SCHED hypercall should be probed using the SMCCC 1.1
 ARCH_FEATURES mechanism before calling it.
@@ -36,6 +37,13 @@ PV_SCHED_IPA_RELEASE
                               this vCPU's PV data structure is released.
     ============= ========    ==========
 
+PV_SCHED_KICK_CPU
+    ============= ========    ==========
+    Function ID:  (uint32)    0xC5000093
+    Return value: (int64)     NOT_SUPPORTED (-1) or SUCCESS (0) if the vCPU is
+                              kicked by the hypervisor.
+    ============= ========    ==========
+
 PV sched state
 --------------
 
@@ -54,3 +62,11 @@ The structure pointed to by the PV_SCHED_IPA hypercall is as follows:
 The preempted field will be updated to 0 by the hypervisor prior to scheduling
 a vCPU. When the vCPU is scheduled out, the preempted field will be updated
 to 1 by the hypervisor.
+
+A vCPU of a paravirtualized guest that is busywaiting in guest kernel mode for
+an event to occur (ex: a spinlock to become available) can execute WFI
+instruction once it has busy-waited for more than a threshold time-interval.
+Execution of WFI instruction would cause the hypervisor to put the vCPU to sleep
+until occurrence of an appropriate event. Another vCPU of the same guest can
+wakeup the sleeping vCPU by issuing PV_SCHED_KICK_CPU hypercall, specifying CPU
+id (reg1) of the vCPU to be woken up.

include/linux/arm-smccc.h

@@ -376,5 +376,11 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, unsigned long a1,
 			   ARM_SMCCC_OWNER_STANDARD_HYP,	\
 			   0x92)
 
+#define ARM_SMCCC_HV_PV_SCHED_KICK_CPU				\
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\
+			   ARM_SMCCC_SMC_64,			\
+			   ARM_SMCCC_OWNER_STANDARD_HYP,	\
+			   0x93)
+
 #endif /*__ASSEMBLY__*/
 #endif /*__LINUX_ARM_SMCCC_H*/