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
This commit is contained in:
Marc Zyngier 2022-09-26 15:51:16 +01:00
parent 8929bc9659
commit 17601bfed9
4 changed files with 24 additions and 2 deletions

View File

@ -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

View File

@ -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

View File

@ -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

View File

@ -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);