KVM: Add KVM_CAP_DIRTY_LOG_RING_ACQ_REL capability and config option

In order to differenciate between architectures that require no extra synchronisation when accessing the dirty ring and those who do, add a new capability (KVM_CAP_DIRTY_LOG_RING_ACQ_REL) that identify the latter sort. TSO architectures can obviously advertise both, while relaxed architectures must only advertise the ACQ_REL version. This requires some configuration symbol rejigging, with HAVE_KVM_DIRTY_RING being only indirectly selected by two top-level config symbols: - HAVE_KVM_DIRTY_RING_TSO for strongly ordered architectures (x86) - HAVE_KVM_DIRTY_RING_ACQ_REL for weakly ordered architectures (arm64)

Marc Zyngier committed 4 years ago

Commit 17601bf1 parent 8929bc94 files · +24 −2Browse files

Unified · Split

4 files

arch/x86/kvm/Kconfig +1 −1
include/uapi/linux/kvm.h +1 −0
virt/kvm/Kconfig +14 −0
virt/kvm/kvm_main.c +8 −1

arch/x86/kvm/Kconfig+1−1

@@ -28,7 +28,7 @@ config KVM · 27 unmodified lines
28	28	select HAVE_KVM_IRQCHIP
29	29	select HAVE_KVM_PFNCACHE
30	30	select HAVE_KVM_IRQFD
31		− select HAVE_KVM_DIRTY_RING
	31	+ select HAVE_KVM_DIRTY_RING_TSO
32	32	select IRQ_BYPASS_MANAGER
33	33	select HAVE_KVM_IRQ_BYPASS
34	34	select HAVE_KVM_IRQ_ROUTING

include/uapi/linux/kvm.h+1−0

@@ -1177,6 +1177,7 @@ struct kvm_ppc_resize_hpt { · 1176 unmodified lines
1177	1177	#define KVM_CAP_VM_DISABLE_NX_HUGE_PAGES 220
1178	1178	#define KVM_CAP_S390_ZPCI_OP 221
1179	1179	#define KVM_CAP_S390_CPU_TOPOLOGY 222
	1180	+#define KVM_CAP_DIRTY_LOG_RING_ACQ_REL 223
1180	1181
1181	1182	#ifdef KVM_CAP_IRQ_ROUTING
1182	1183

virt/kvm/Kconfig+14−0

@@ -19,6 +19,20 @@ config HAVE_KVM_IRQ_ROUTING · 18 unmodified lines
19	19	config HAVE_KVM_DIRTY_RING
20	20	bool
21	21
	22	+# Only strongly ordered architectures can select this, as it doesn't
	23	+# put any explicit constraint on userspace ordering. They can also
	24	+# select the _ACQ_REL version.
	25	+config HAVE_KVM_DIRTY_RING_TSO
	26	+ bool
	27	+ select HAVE_KVM_DIRTY_RING
	28	+ depends on X86
	29	+
	30	+# Weakly ordered architectures can only select this, advertising
	31	+# to userspace the additional ordering requirements.
	32	+config HAVE_KVM_DIRTY_RING_ACQ_REL
	33	+ bool
	34	+ select HAVE_KVM_DIRTY_RING
	35	+
22	36	config HAVE_KVM_EVENTFD
23	37	bool
24	38	select EVENTFD

virt/kvm/kvm_main.c+8−1

@@ -4475,7 +4475,13 @@ static long kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg) · 4474 unmodified lines
4475	4475	case KVM_CAP_NR_MEMSLOTS:
4476	4476	return KVM_USER_MEM_SLOTS;
4477	4477	case KVM_CAP_DIRTY_LOG_RING:
4478		−#ifdef CONFIG_HAVE_KVM_DIRTY_RING
	4478	+#ifdef CONFIG_HAVE_KVM_DIRTY_RING_TSO
	4479	+ return KVM_DIRTY_RING_MAX_ENTRIES * sizeof(struct kvm_dirty_gfn);
	4480	+#else
	4481	+ return 0;
	4482	+#endif
	4483	+ case KVM_CAP_DIRTY_LOG_RING_ACQ_REL:
	4484	+#ifdef CONFIG_HAVE_KVM_DIRTY_RING_ACQ_REL
4479	4485	return KVM_DIRTY_RING_MAX_ENTRIES * sizeof(struct kvm_dirty_gfn);
4480	4486	#else
4481	4487	return 0;
@@ -4580,6 +4586,7 @@ static int kvm_vm_ioctl_enable_cap_generic(struct kvm *kvm, · 98 unmodified lines
4580	4586	return 0;
4581	4587	}
4582	4588	case KVM_CAP_DIRTY_LOG_RING:
	4589	+ case KVM_CAP_DIRTY_LOG_RING_ACQ_REL:
4583	4590	return kvm_vm_ioctl_enable_dirty_log_ring(kvm, cap->args[0]);
4584	4591	default:
4585	4592	return kvm_vm_ioctl_enable_cap(kvm, cap);