KVM: kvm-io: support cookies

Add new functions kvm_io_bus_{read,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>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index a63d83e..ec590ae 100644 (file)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -160,8 +160,12 @@ 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_read_cookie(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
+                          int len, void *val, long cookie);
 int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
                            int len, struct kvm_io_device *dev);
 int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 1580dd4..71960fb 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2863,13 +2863,33 @@ static int kvm_io_bus_get_first_dev(struct kvm_io_bus *bus,
        return off;
 }
 
+static int __kvm_io_bus_write(struct kvm_io_bus *bus,
+                             struct kvm_io_range *range, const void *val)
+{
+       int idx;
+
+       idx = kvm_io_bus_get_first_dev(bus, range->addr, range->len);
+       if (idx < 0)
+               return -EOPNOTSUPP;
+
+       while (idx < bus->dev_count &&
+               kvm_io_bus_sort_cmp(range, &bus->range[idx]) == 0) {
+               if (!kvm_iodevice_write(bus->range[idx].dev, range->addr,
+                                       range->len, val))
+                       return idx;
+               idx++;
+       }
+
+       return -EOPNOTSUPP;
+}
+
 /* kvm_io_bus_write - called under kvm->slots_lock */
 int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
                     int len, const void *val)
 {
-       int idx;
        struct kvm_io_bus *bus;
        struct kvm_io_range range;
+       int r;
 
        range = (struct kvm_io_range) {
                .addr = addr,
@@ -2877,14 +2897,52 @@ int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
        };
 
        bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu);
-       idx = kvm_io_bus_get_first_dev(bus, addr, len);
+       r = __kvm_io_bus_write(bus, &range, val);
+       return r < 0 ? r : 0;
+}
+
+/* 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)
+{
+       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 cookie;
+
+       /*
+        * cookie contained garbage; fall back to search and return the
+        * correct cookie value.
+        */
+       return __kvm_io_bus_write(bus, &range, val);
+}
+
+static int __kvm_io_bus_read(struct kvm_io_bus *bus, struct kvm_io_range *range,
+                            void *val)
+{
+       int idx;
+
+       idx = kvm_io_bus_get_first_dev(bus, range->addr, range->len);
        if (idx < 0)
                return -EOPNOTSUPP;
 
        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))
-                       return 0;
+               kvm_io_bus_sort_cmp(range, &bus->range[idx]) == 0) {
+               if (!kvm_iodevice_read(bus->range[idx].dev, range->addr,
+                                      range->len, val))
+                       return idx;
                idx++;
        }
 
@@ -2895,9 +2953,9 @@ int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
 int kvm_io_bus_read(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
                    int len, void *val)
 {
-       int idx;
        struct kvm_io_bus *bus;
        struct kvm_io_range range;
+       int r;
 
        range = (struct kvm_io_range) {
                .addr = addr,
@@ -2905,18 +2963,36 @@ int kvm_io_bus_read(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
        };
 
        bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu);
-       idx = kvm_io_bus_get_first_dev(bus, addr, len);
-       if (idx < 0)
-               return -EOPNOTSUPP;
+       r = __kvm_io_bus_read(bus, &range, val);
+       return r < 0 ? r : 0;
+}
 
-       while (idx < bus->dev_count &&
-               kvm_io_bus_sort_cmp(&range, &bus->range[idx]) == 0) {
-               if (!kvm_iodevice_read(bus->range[idx].dev, addr, len, val))
-                       return 0;
-               idx++;
-       }
+/* kvm_io_bus_read_cookie - called under kvm->slots_lock */
+int kvm_io_bus_read_cookie(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
+                          int len, void *val, long cookie)
+{
+       struct kvm_io_bus *bus;
+       struct kvm_io_range range;
 
-       return -EOPNOTSUPP;
+       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_read(bus->range[cookie].dev, addr, len,
+                                      val))
+                       return cookie;
+
+       /*
+        * cookie contained garbage; fall back to search and return the
+        * correct cookie value.
+        */
+       return __kvm_io_bus_read(bus, &range, val);
 }
 
 /* Caller must hold slots_lock. */