KVM: Add support for enabling capabilities per-vcpu

Some times we don't want all capabilities to be available to all our vcpus. One example for that is the OSI interface, implemented in the next patch. In order to have a generic mechanism in how to enable capabilities individually, this patch introduces a new ioctl that can be used for this purpose. That way features we don't want in all guests or userspace configurations can just not be enabled and we're good. Signed-off-by: Alexander Graf <agraf@suse.de> Signed-off-by: Avi Kivity <avi@redhat.com>

KVM: Add support for enabling capabilities per-vcpu
Some times we don't want all capabilities to be available to all our vcpus. One example for that is the OSI interface, implemented in the next patch. In order to have a generic mechanism in how to enable capabilities individually, this patch introduces a new ioctl that can be used for this purpose. That way features we don't want in all guests or userspace configurations can just not be enabled and we're good. Signed-off-by: Alexander Graf <agraf@suse.de> Signed-off-by: Avi Kivity <avi@redhat.com>
Alexander Graf · Avi Kivity
1 parent ca7f4203b9
Showing 3 changed files with 73 additions and 0 deletions Side-by-side Diff
Documentation/kvm/api.txt
arch/powerpc/kvm/powerpc.c
include/linux/kvm.h
@@ -813,6 +813,41 @@
 because of a quirk in the virtualization implementation (see the internals
 documentation when it pops into existence).
  
+4.36 KVM_ENABLE_CAP
+
+Capability: KVM_CAP_ENABLE_CAP
+Architectures: ppc
+Type: vcpu ioctl
+Parameters: struct kvm_enable_cap (in)
+Returns: 0 on success; -1 on error
+
++Not all extensions are enabled by default. Using this ioctl the application
+can enable an extension, making it available to the guest.
+
+On systems that do not support this ioctl, it always fails. On systems that
+do support it, it only works for extensions that are supported for enablement.
+
+To check if a capability can be enabled, the KVM_CHECK_EXTENSION ioctl should
+be used.
+
+struct kvm_enable_cap {
+       /* in */
+       __u32 cap;
+
+The capability that is supposed to get enabled.
+
+       __u32 flags;
+
+A bitfield indicating future enhancements. Has to be 0 for now.
+
+       __u64 args[4];
+
+Arguments for enabling a feature. If a feature needs initial values to
+function properly, this is the place to put them.
+
+       __u8  pad[64];
+};
+
 5. The kvm_run structure
  
 Application code obtains a pointer to the kvm_run structure by
@@ -150,6 +150,7 @@
 	case KVM_CAP_PPC_SEGSTATE:
 	case KVM_CAP_PPC_PAIRED_SINGLES:
 	case KVM_CAP_PPC_UNSET_IRQ:
+	case KVM_CAP_ENABLE_CAP:
 		r = 1;
 		break;
 	case KVM_CAP_COALESCED_MMIO:
@@ -465,6 +466,23 @@
 	return 0;
 }
  
+static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
+				     struct kvm_enable_cap *cap)
+{
+	int r;
+
+	if (cap->flags)
+		return -EINVAL;
+
+	switch (cap->cap) {
+	default:
+		r = -EINVAL;
+		break;
+	}
+
+	return r;
+}
+
 int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu,
                                     struct kvm_mp_state *mp_state)
 {
@@ -491,6 +509,15 @@
 		if (copy_from_user(&irq, argp, sizeof(irq)))
 			goto out;
 		r = kvm_vcpu_ioctl_interrupt(vcpu, &irq);
+		break;
+	}
+	case KVM_ENABLE_CAP:
+	{
+		struct kvm_enable_cap cap;
+		r = -EFAULT;
+		if (copy_from_user(&cap, argp, sizeof(cap)))
+			goto out;
+		r = kvm_vcpu_ioctl_enable_cap(vcpu, &cap);
 		break;
 	}
 	default:
@@ -400,6 +400,15 @@
 	__u8  pad[36];
 };
  
+/* for KVM_ENABLE_CAP */
+struct kvm_enable_cap {
+	/* in */
+	__u32 cap;
+	__u32 flags;
+	__u64 args[4];
+	__u8  pad[64];
+};
+
 #define KVMIO 0xAE
  
 /*
@@ -508,6 +517,7 @@
 #endif
 #define KVM_CAP_X86_ROBUST_SINGLESTEP 51
 #define KVM_CAP_PPC_UNSET_IRQ 53
+#define KVM_CAP_ENABLE_CAP 54
  
 #ifdef KVM_CAP_IRQ_ROUTING
  
@@ -697,6 +707,7 @@
 /* Available with KVM_CAP_DEBUGREGS */
 #define KVM_GET_DEBUGREGS         _IOR(KVMIO,  0xa1, struct kvm_debugregs)
 #define KVM_SET_DEBUGREGS         _IOW(KVMIO,  0xa2, struct kvm_debugregs)
+#define KVM_ENABLE_CAP            _IOW(KVMIO,  0xa3, struct kvm_enable_cap)
  
 #define KVM_DEV_ASSIGN_ENABLE_IOMMU	(1 << 0)
...	...	@@ -813,6 +813,41 @@
813	813	because of a quirk in the virtualization implementation (see the internals
814	814	documentation when it pops into existence).
815	815
	816	+4.36 KVM_ENABLE_CAP
	817	+
	818	+Capability: KVM_CAP_ENABLE_CAP
	819	+Architectures: ppc
	820	+Type: vcpu ioctl
	821	+Parameters: struct kvm_enable_cap (in)
	822	+Returns: 0 on success; -1 on error
	823	+
	824	++Not all extensions are enabled by default. Using this ioctl the application
	825	+can enable an extension, making it available to the guest.
	826	+
	827	+On systems that do not support this ioctl, it always fails. On systems that
	828	+do support it, it only works for extensions that are supported for enablement.
	829	+
	830	+To check if a capability can be enabled, the KVM_CHECK_EXTENSION ioctl should
	831	+be used.
	832	+
	833	+struct kvm_enable_cap {
	834	+ /* in */
	835	+ __u32 cap;
	836	+
	837	+The capability that is supposed to get enabled.
	838	+
	839	+ __u32 flags;
	840	+
	841	+A bitfield indicating future enhancements. Has to be 0 for now.
	842	+
	843	+ __u64 args[4];
	844	+
	845	+Arguments for enabling a feature. If a feature needs initial values to
	846	+function properly, this is the place to put them.
	847	+
	848	+ __u8 pad[64];
	849	+};
	850	+
816	851	5. The kvm_run structure
817	852
818	853	Application code obtains a pointer to the kvm_run structure by
...	...	@@ -150,6 +150,7 @@
150	150	case KVM_CAP_PPC_SEGSTATE:
151	151	case KVM_CAP_PPC_PAIRED_SINGLES:
152	152	case KVM_CAP_PPC_UNSET_IRQ:
	153	+ case KVM_CAP_ENABLE_CAP:
153	154	r = 1;
154	155	break;
155	156	case KVM_CAP_COALESCED_MMIO:
...	...	@@ -465,6 +466,23 @@
465	466	return 0;
466	467	}
467	468
	469	+static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
	470	+ struct kvm_enable_cap *cap)
	471	+{
	472	+ int r;
	473	+
	474	+ if (cap->flags)
	475	+ return -EINVAL;
	476	+
	477	+ switch (cap->cap) {
	478	+ default:
	479	+ r = -EINVAL;
	480	+ break;
	481	+ }
	482	+
	483	+ return r;
	484	+}
	485	+
468	486	int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu,
469	487	struct kvm_mp_state *mp_state)
470	488	{
...	...	@@ -491,6 +509,15 @@
491	509	if (copy_from_user(&irq, argp, sizeof(irq)))
492	510	goto out;
493	511	r = kvm_vcpu_ioctl_interrupt(vcpu, &irq);
	512	+ break;
	513	+ }
	514	+ case KVM_ENABLE_CAP:
	515	+ {
	516	+ struct kvm_enable_cap cap;
	517	+ r = -EFAULT;
	518	+ if (copy_from_user(&cap, argp, sizeof(cap)))
	519	+ goto out;
	520	+ r = kvm_vcpu_ioctl_enable_cap(vcpu, &cap);
494	521	break;
495	522	}
496	523	default:
...	...	@@ -400,6 +400,15 @@
400	400	__u8 pad[36];
401	401	};
402	402
	403	+/* for KVM_ENABLE_CAP */
	404	+struct kvm_enable_cap {
	405	+ /* in */
	406	+ __u32 cap;
	407	+ __u32 flags;
	408	+ __u64 args[4];
	409	+ __u8 pad[64];
	410	+};
	411	+
403	412	#define KVMIO 0xAE
404	413
405	414	/*
...	...	@@ -508,6 +517,7 @@
508	517	#endif
509	518	#define KVM_CAP_X86_ROBUST_SINGLESTEP 51
510	519	#define KVM_CAP_PPC_UNSET_IRQ 53
	520	+#define KVM_CAP_ENABLE_CAP 54
511	521
512	522	#ifdef KVM_CAP_IRQ_ROUTING
513	523
...	...	@@ -697,6 +707,7 @@
697	707	/* Available with KVM_CAP_DEBUGREGS */
698	708	#define KVM_GET_DEBUGREGS _IOR(KVMIO, 0xa1, struct kvm_debugregs)
699	709	#define KVM_SET_DEBUGREGS _IOW(KVMIO, 0xa2, struct kvm_debugregs)
	710	+#define KVM_ENABLE_CAP _IOW(KVMIO, 0xa3, struct kvm_enable_cap)
700	711
701	712	#define KVM_DEV_ASSIGN_ENABLE_IOMMU (1 << 0)
702	713