[patch 2/3] KVM: x86: introduce ioctl to allow frequency hypercalls

[Marcelo Tosatti]

For most VMs, modifying the host frequency is an undesired 
operation. Introduce ioctl to enable the guest to 
modify host CPU frequency.


Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
---
 arch/x86/include/asm/kvm_host.h |    2 ++
 arch/x86/include/uapi/asm/kvm.h |    5 +++++
 arch/x86/kvm/x86.c              |   20 ++++++++++++++++++++
 include/uapi/linux/kvm.h        |    3 +++
 virt/kvm/kvm_main.c             |    2 ++
 5 files changed, 32 insertions(+)

Index: kvm-pvfreq/arch/x86/kvm/x86.c
===================================================================
--- kvm-pvfreq.orig/arch/x86/kvm/x86.c	2017-01-31 10:32:33.023378783 -0200
+++ kvm-pvfreq/arch/x86/kvm/x86.c	2017-01-31 10:34:25.443618639 -0200
@@ -3665,6 +3665,26 @@
 		r = kvm_vcpu_ioctl_enable_cap(vcpu, &cap);
 		break;
 	}
+	case KVM_SET_VCPU_ALLOW_FREQ_HC: {
+		struct kvm_vcpu_allow_freq freq;
+
+		r = -EFAULT;
+		if (copy_from_user(&freq, argp, sizeof(freq)))
+			goto out;
+		vcpu->arch.allow_freq_hypercall = freq.enable;
+		r = 0;
+		break;
+	}
+	case KVM_GET_VCPU_ALLOW_FREQ_HC: {
+		struct kvm_vcpu_allow_freq freq;
+
+		memset(&freq, 0, sizeof(struct kvm_vcpu_allow_freq));
+		r = -EFAULT;
+		if (copy_to_user(&freq, argp, sizeof(freq)))
+			break;
+		r = 0;
+		break;
+	}
 	default:
 		r = -EINVAL;
 	}
Index: kvm-pvfreq/include/uapi/linux/kvm.h
===================================================================
--- kvm-pvfreq.orig/include/uapi/linux/kvm.h	2017-01-31 10:32:33.023378783 -0200
+++ kvm-pvfreq/include/uapi/linux/kvm.h	2017-01-31 10:32:38.000389402 -0200
@@ -871,6 +871,7 @@
 #define KVM_CAP_S390_USER_INSTR0 130
 #define KVM_CAP_MSI_DEVID 131
 #define KVM_CAP_PPC_HTM 132
+#define KVM_CAP_ALLOW_FREQ_HC 133
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
@@ -1281,6 +1282,8 @@
 #define KVM_S390_GET_IRQ_STATE	  _IOW(KVMIO, 0xb6, struct kvm_s390_irq_state)
 /* Available with KVM_CAP_X86_SMM */
 #define KVM_SMI                   _IO(KVMIO,   0xb7)
+#define KVM_SET_VCPU_ALLOW_FREQ_HC   _IO(KVMIO,   0xb8)
+#define KVM_GET_VCPU_ALLOW_FREQ_HC   _IO(KVMIO,   0xb9)
 
 #define KVM_DEV_ASSIGN_ENABLE_IOMMU	(1 << 0)
 #define KVM_DEV_ASSIGN_PCI_2_3		(1 << 1)
Index: kvm-pvfreq/arch/x86/include/uapi/asm/kvm.h
===================================================================
--- kvm-pvfreq.orig/arch/x86/include/uapi/asm/kvm.h	2017-01-31 10:32:33.023378783 -0200
+++ kvm-pvfreq/arch/x86/include/uapi/asm/kvm.h	2017-01-31 10:32:38.000389402 -0200
@@ -357,4 +357,9 @@
 #define KVM_X86_QUIRK_LINT0_REENABLED	(1 << 0)
 #define KVM_X86_QUIRK_CD_NW_CLEARED	(1 << 1)
 
+struct kvm_vcpu_allow_freq {
+	__u16 enable;
+	__u16 pad[7];
+};
+
 #endif /* _ASM_X86_KVM_H */
Index: kvm-pvfreq/virt/kvm/kvm_main.c
===================================================================
--- kvm-pvfreq.orig/virt/kvm/kvm_main.c	2017-01-31 10:32:33.023378783 -0200
+++ kvm-pvfreq/virt/kvm/kvm_main.c	2017-01-31 10:32:38.001389404 -0200
@@ -2938,6 +2938,8 @@
 #endif
 	case KVM_CAP_MAX_VCPU_ID:
 		return KVM_MAX_VCPU_ID;
+	case KVM_CAP_ALLOW_FREQ_HC:
+		return 1;
 	default:
 		break;
 	}
Index: kvm-pvfreq/arch/x86/include/asm/kvm_host.h
===================================================================
--- kvm-pvfreq.orig/arch/x86/include/asm/kvm_host.h	2017-01-31 10:32:33.023378783 -0200
+++ kvm-pvfreq/arch/x86/include/asm/kvm_host.h	2017-01-31 10:32:38.001389404 -0200
@@ -678,6 +678,8 @@
 
 	/* GPA available (AMD only) */
 	bool gpa_available;
+
+	bool allow_freq_hypercall;
 };
 
 struct kvm_lpage_info {