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authorMichael S. Tsirkin <mst@redhat.com>2014-03-31 21:50:38 +0300
committerMarcelo Tosatti <mtosatti@redhat.com>2014-04-17 14:01:42 -0300
commitf848a5a8dcb655553423f77cc98909a04e64173d (patch)
tree02e212c8eeeb52e74876408bb5e7e5d2febae379 /virt
parentcd9ae5fe47dfb9820976c3c38c70f4b07a5a1c36 (diff)
KVM: support any-length wildcard ioeventfd
It is sometimes benefitial to ignore IO size, and only match on address. In hindsight this would have been a better default than matching length when KVM_IOEVENTFD_FLAG_DATAMATCH is not set, In particular, this kind of access can be optimized on VMX: there no need to do page lookups. This can currently be done with many ioeventfds but in a suboptimal way. However we can't change kernel/userspace ABI without risk of breaking some applications. Use len = 0 to mean "ignore length for matching" in a more optimal way. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/eventfd.c27
1 files changed, 22 insertions, 5 deletions
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 29c2a04e036..2721996bb9c 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -600,7 +600,15 @@ ioeventfd_in_range(struct _ioeventfd *p, gpa_t addr, int len, const void *val)
{
u64 _val;
- if (!(addr == p->addr && len == p->length))
+ if (addr != p->addr)
+ /* address must be precise for a hit */
+ return false;
+
+ if (!p->length)
+ /* length = 0 means only look at the address, so always a hit */
+ return true;
+
+ if (len != p->length)
/* address-range must be precise for a hit */
return false;
@@ -671,9 +679,11 @@ ioeventfd_check_collision(struct kvm *kvm, struct _ioeventfd *p)
list_for_each_entry(_p, &kvm->ioeventfds, list)
if (_p->bus_idx == p->bus_idx &&
- _p->addr == p->addr && _p->length == p->length &&
- (_p->wildcard || p->wildcard ||
- _p->datamatch == p->datamatch))
+ _p->addr == p->addr &&
+ (!_p->length || !p->length ||
+ (_p->length == p->length &&
+ (_p->wildcard || p->wildcard ||
+ _p->datamatch == p->datamatch))))
return true;
return false;
@@ -697,8 +707,9 @@ kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
int ret;
bus_idx = ioeventfd_bus_from_flags(args->flags);
- /* must be natural-word sized */
+ /* must be natural-word sized, or 0 to ignore length */
switch (args->len) {
+ case 0:
case 1:
case 2:
case 4:
@@ -716,6 +727,12 @@ kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
if (args->flags & ~KVM_IOEVENTFD_VALID_FLAG_MASK)
return -EINVAL;
+ /* ioeventfd with no length can't be combined with DATAMATCH */
+ if (!args->len &&
+ args->flags & (KVM_IOEVENTFD_FLAG_PIO |
+ KVM_IOEVENTFD_FLAG_DATAMATCH))
+ return -EINVAL;
+
eventfd = eventfd_ctx_fdget(args->fd);
if (IS_ERR(eventfd))
return PTR_ERR(eventfd);