[patch 1/3] KVM: x86: add per-vcpu option to set guest vcpu -RT priority

[Marcelo Tosatti <mtosatti@xxxxxxxxxx>]

In preparation to the patch which adds a hypercall for 
the guest vcpu to change states between: 

	-> SCHED_FIFO.
	-> SCHED_NORMAL.

Add controls to:

	1) Allow control to which priority SCHED_FIFO state will be in
	   place (in the host).

	2) Enable/disable ability to use the hypercall, on a per-vcpu
	   basis.


Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>

---
 arch/x86/include/asm/kvm_host.h |    4 ++++
 arch/x86/include/uapi/asm/kvm.h |    5 +++++
 arch/x86/kvm/x86.c              |   29 +++++++++++++++++++++++++++++
 include/uapi/linux/kvm.h        |    3 +++
 4 files changed, 41 insertions(+)

Index: kvm.fifopriohc-submit/arch/x86/include/asm/kvm_host.h
===================================================================
--- kvm.fifopriohc-submit.orig/arch/x86/include/asm/kvm_host.h
+++ kvm.fifopriohc-submit/arch/x86/include/asm/kvm_host.h
@@ -688,6 +688,10 @@ struct kvm_vcpu_arch {
 
 	/* GPA available (AMD only) */
 	bool gpa_available;
+
+	/* Enable RT prio hypercall */
+	bool enable_rt_prio_hc;
+	int rt_sched_priority;
 };
 
 struct kvm_lpage_info {
Index: kvm.fifopriohc-submit/arch/x86/kvm/x86.c
===================================================================
--- kvm.fifopriohc-submit.orig/arch/x86/kvm/x86.c
+++ kvm.fifopriohc-submit/arch/x86/kvm/x86.c
@@ -2683,6 +2683,7 @@ int kvm_vm_ioctl_check_extension(struct
 	case KVM_CAP_SET_BOOT_CPU_ID:
  	case KVM_CAP_SPLIT_IRQCHIP:
 	case KVM_CAP_IMMEDIATE_EXIT:
+	case KVM_CAP_VCPU_RT_PRIO_HC:
 		r = 1;
 		break;
 	case KVM_CAP_ADJUST_CLOCK:
@@ -3386,6 +3387,25 @@ static int kvm_set_guest_paused(struct k
 	return 0;
 }
 
+static int kvm_vcpu_ioctl_set_rt_prio_hc(struct kvm_vcpu *vcpu,
+					    struct kvm_vcpu_rt_prio *rt_prio)
+{
+	if (rt_prio->enabled == 0) {
+		vcpu->arch.enable_rt_prio_hc = false;
+		return 0;
+	}
+
+	if (rt_prio->sched_priority < 1 ||
+	    rt_prio->sched_priority > 99)
+		return -EINVAL;
+
+
+	vcpu->arch.enable_rt_prio_hc = true;
+	vcpu->arch.rt_sched_priority = rt_prio->sched_priority;
+
+	return 0;
+}
+
 static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
 				     struct kvm_enable_cap *cap)
 {
@@ -3682,6 +3702,15 @@ long kvm_arch_vcpu_ioctl(struct file *fi
 		r = kvm_vcpu_ioctl_enable_cap(vcpu, &cap);
 		break;
 	}
+	case KVM_SET_VCPU_RT_PRIO_HC: {
+		struct kvm_vcpu_rt_prio rt_prio;
+
+		r = -EFAULT;
+		if (copy_from_user(&rt_prio, argp, sizeof(rt_prio)))
+			goto out;
+		r = kvm_vcpu_ioctl_set_rt_prio_hc(vcpu, &rt_prio);
+		break;
+	}
 	default:
 		r = -EINVAL;
 	}
Index: kvm.fifopriohc-submit/include/uapi/linux/kvm.h
===================================================================
--- kvm.fifopriohc-submit.orig/include/uapi/linux/kvm.h
+++ kvm.fifopriohc-submit/include/uapi/linux/kvm.h
@@ -929,6 +929,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_PPC_SMT_POSSIBLE 147
 #define KVM_CAP_HYPERV_SYNIC2 148
 #define KVM_CAP_HYPERV_VP_INDEX 149
+#define KVM_CAP_VCPU_RT_PRIO_HC 150
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
@@ -1355,6 +1356,8 @@ struct kvm_s390_ucas_mapping {
 /* Available with KVM_CAP_S390_CMMA_MIGRATION */
 #define KVM_S390_GET_CMMA_BITS      _IOWR(KVMIO, 0xb8, struct kvm_s390_cmma_log)
 #define KVM_S390_SET_CMMA_BITS      _IOW(KVMIO, 0xb9, struct kvm_s390_cmma_log)
+/* Available with KVM_CAP_VCPU_RT_PRIO_HC */
+#define KVM_SET_VCPU_RT_PRIO_HC	_IOW(KVMIO, 0xba, struct kvm_vcpu_rt_prio)
 
 #define KVM_DEV_ASSIGN_ENABLE_IOMMU	(1 << 0)
 #define KVM_DEV_ASSIGN_PCI_2_3		(1 << 1)
Index: kvm.fifopriohc-submit/arch/x86/include/uapi/asm/kvm.h
===================================================================
--- kvm.fifopriohc-submit.orig/arch/x86/include/uapi/asm/kvm.h
+++ kvm.fifopriohc-submit/arch/x86/include/uapi/asm/kvm.h
@@ -353,6 +353,11 @@ struct kvm_xcrs {
 	__u64 padding[16];
 };
 
+struct kvm_vcpu_rt_prio {
+	__u32 enabled;
+	__u32 sched_priority;
+};
+
 /* definition of registers in kvm_run */
 struct kvm_sync_regs {
 };