[PATCH 1/2] KVM: kvm-io: support cookies

Cornelia Huck
2013-07-03T08:56:26Z

Add a new function kvm_io_bus_write_cookie() that allows users of the
kvm io infrastructure to use a cookie value to speed up lookup of a
device on an io bus.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
---
include/linux/kvm_host.h | 2 ++
virt/kvm/kvm_main.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 46 insertions(+)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index e3aae6d..2d298fc 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -159,6 +159,8 @@ enum kvm_bus {

int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
int len, const void *val);
+int kvm_io_bus_write_cookie(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
+ int len, const void *val, long *cookie);
int kvm_io_bus_read(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, int len,
void *val);
int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 1580dd4..222475a 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2891,6 +2891,50 @@ int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
return -EOPNOTSUPP;
}

+/* kvm_io_bus_write_cookie - called under kvm->slots_lock */
+int kvm_io_bus_write_cookie(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
+ int len, const void *val, long *cookie)
+{
+ int idx, ret = -EOPNOTSUPP;
+ struct kvm_io_bus *bus;
+ struct kvm_io_range range;
+
+ range = (struct kvm_io_range) {
+ .addr = addr,
+ .len = len,
+ };
+
+ bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu);
+
+ /* First try the device referenced by *cookie. */
+ if ((*cookie >= 0) && (*cookie < bus->dev_count) &&
+ (kvm_io_bus_sort_cmp(&range, &bus->range[*cookie]) == 0))
+ if (!kvm_iodevice_write(bus->range[*cookie].dev, addr, len,
+ val))
+ return 0;
+
+ /*
+ * *cookie contained garbage; fall back to search and return the
+ * correct value in *cookie.
+ */
+ idx = kvm_io_bus_get_first_dev(bus, addr, len);
+ if (idx < 0)
+ goto out;
+
+ while (idx < bus->dev_count &&
+ kvm_io_bus_sort_cmp(&range, &bus->range[idx]) == 0) {
+ if (!kvm_iodevice_write(bus->range[idx].dev, addr, len, val)) {
+ ret = 0;
+ goto out;
+ }
+ idx++;
+ }
+ idx = -ENOENT;
+out:
+ *cookie = idx;
+ return ret;
+}
+
/* kvm_io_bus_read - called under kvm->slots_lock */
int kvm_io_bus_read(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
int len, void *val)
--
1.8.2.2