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authorMarc Zyngier <maz@kernel.org>2022-09-26 16:51:16 +0200
committerMarc Zyngier <maz@kernel.org>2022-09-29 11:23:08 +0200
commit17601bfed909fa080fcfd227b57da2bd4dc2d2a6 (patch)
tree79e7babcef9a32617591bd2147206b00dab25714
parentKVM: Use acquire/release semantics when accessing dirty ring GFN state (diff)
downloadlinux-17601bfed909fa080fcfd227b57da2bd4dc2d2a6.tar.xz
linux-17601bfed909fa080fcfd227b57da2bd4dc2d2a6.zip
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) Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Marc Zyngier <maz@kernel.org> Reviewed-by: Gavin Shan <gshan@redhat.com> Reviewed-by: Peter Xu <peterx@redhat.com> Link: https://lore.kernel.org/r/20220926145120.27974-3-maz@kernel.org
-rw-r--r--arch/x86/kvm/Kconfig2
-rw-r--r--include/uapi/linux/kvm.h1
-rw-r--r--virt/kvm/Kconfig14
-rw-r--r--virt/kvm/kvm_main.c9
4 files changed, 24 insertions, 2 deletions
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index e3cbd7706136..876748b236ff 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -28,7 +28,7 @@ config KVM
select HAVE_KVM_IRQCHIP
select HAVE_KVM_PFNCACHE
select HAVE_KVM_IRQFD
- select HAVE_KVM_DIRTY_RING
+ select HAVE_KVM_DIRTY_RING_TSO
select IRQ_BYPASS_MANAGER
select HAVE_KVM_IRQ_BYPASS
select HAVE_KVM_IRQ_ROUTING
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index eed0315a77a6..0d5d4419139a 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1177,6 +1177,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_VM_DISABLE_NX_HUGE_PAGES 220
#define KVM_CAP_S390_ZPCI_OP 221
#define KVM_CAP_S390_CPU_TOPOLOGY 222
+#define KVM_CAP_DIRTY_LOG_RING_ACQ_REL 223
#ifdef KVM_CAP_IRQ_ROUTING
diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index a8c5c9f06b3c..800f9470e36b 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -19,6 +19,20 @@ config HAVE_KVM_IRQ_ROUTING
config HAVE_KVM_DIRTY_RING
bool
+# Only strongly ordered architectures can select this, as it doesn't
+# put any explicit constraint on userspace ordering. They can also
+# select the _ACQ_REL version.
+config HAVE_KVM_DIRTY_RING_TSO
+ bool
+ select HAVE_KVM_DIRTY_RING
+ depends on X86
+
+# Weakly ordered architectures can only select this, advertising
+# to userspace the additional ordering requirements.
+config HAVE_KVM_DIRTY_RING_ACQ_REL
+ bool
+ select HAVE_KVM_DIRTY_RING
+
config HAVE_KVM_EVENTFD
bool
select EVENTFD
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 584a5bab3af3..5b064dbadaf4 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4475,7 +4475,13 @@ static long kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
case KVM_CAP_NR_MEMSLOTS:
return KVM_USER_MEM_SLOTS;
case KVM_CAP_DIRTY_LOG_RING:
-#ifdef CONFIG_HAVE_KVM_DIRTY_RING
+#ifdef CONFIG_HAVE_KVM_DIRTY_RING_TSO
+ return KVM_DIRTY_RING_MAX_ENTRIES * sizeof(struct kvm_dirty_gfn);
+#else
+ return 0;
+#endif
+ case KVM_CAP_DIRTY_LOG_RING_ACQ_REL:
+#ifdef CONFIG_HAVE_KVM_DIRTY_RING_ACQ_REL
return KVM_DIRTY_RING_MAX_ENTRIES * sizeof(struct kvm_dirty_gfn);
#else
return 0;
@@ -4580,6 +4586,7 @@ static int kvm_vm_ioctl_enable_cap_generic(struct kvm *kvm,
return 0;
}
case KVM_CAP_DIRTY_LOG_RING:
+ case KVM_CAP_DIRTY_LOG_RING_ACQ_REL:
return kvm_vm_ioctl_enable_dirty_log_ring(kvm, cap->args[0]);
default:
return kvm_vm_ioctl_enable_cap(kvm, cap);