Drivers: hv: vmbus: Resolve more races involving init_vp_index()

init_vp_index() uses the (per-node) hv_numa_map[] masks to record the
CPUs allocated for channel interrupts at a given time, and distribute
the performance-critical channels across the available CPUs: in part.,
the mask of "candidate" target CPUs in a given NUMA node, for a newly
offered channel, is determined by XOR-ing the node's CPU mask and the
node's hv_numa_map.  This operation/mechanism assumes that no offline
CPUs is set in the hv_numa_map mask, an assumption that does not hold
since such mask is currently not updated when a channel is removed or
assigned to a different CPU.

To address the issues described above, this adds hooks in the channel
removal path (hv_process_channel_removal()) and in target_cpu_store()
in order to clear, resp. to update, the hv_numa_map[] masks as needed.
This also adds a (missed) update of the masks in init_vp_index() (cf.,
e.g., the memory-allocation failure path in this function).

Like in the case of init_vp_index(), such hooks require to determine
if the given channel is performance critical.  init_vp_index() does
this by parsing the channel's offer, it can not rely on the device
data structure (device_obj) to retrieve such information because the
device data structure has not been allocated/linked with the channel
by the time that init_vp_index() executes.  A similar situation may
hold in hv_is_alloced_cpu() (defined below); the adopted approach is
to "cache" the device type of the channel, as computed by parsing the
channel's offer, in the channel structure itself.

Fixes: 7527810573436f ("Drivers: hv: vmbus: Introduce the CHANNELMSG_MODIFYCHANNEL message type")
Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20200522171901.204127-3-parri.andrea@gmail.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 89eaacf..417a95e 100644 (file)
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -24,9 +24,9 @@
 
 #include "hyperv_vmbus.h"
 
-static void init_vp_index(struct vmbus_channel *channel, u16 dev_type);
+static void init_vp_index(struct vmbus_channel *channel);
 
-static const struct vmbus_device vmbus_devs[] = {
+const struct vmbus_device vmbus_devs[] = {
        /* IDE */
        { .dev_type = HV_IDE,
          HV_IDE_GUID,
@@ -432,6 +432,13 @@ void hv_process_channel_removal(struct vmbus_channel *channel)
        }
 
        /*
+        * If this is a "perf" channel, updates the hv_numa_map[] masks so that
+        * init_vp_index() can (re-)use the CPU.
+        */
+       if (hv_is_perf_channel(channel))
+               hv_clear_alloced_cpu(channel->target_cpu);
+
+       /*
         * Upon suspend, an in-use hv_sock channel is marked as "rescinded" and
         * the relid is invalidated; after hibernation, when the user-space app
         * destroys the channel, the relid is INVALID_RELID, and in this case
@@ -497,7 +504,7 @@ static void vmbus_add_channel_work(struct work_struct *work)
        if (!newchannel->device_obj)
                goto err_deq_chan;
 
-       newchannel->device_obj->device_id = hv_get_dev_type(newchannel);
+       newchannel->device_obj->device_id = newchannel->device_id;
        /*
         * Add the new device to the bus. This will kick off device-driver
         * binding which eventually invokes the device driver's AddDevice()
@@ -580,7 +587,7 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel)
         */
        mutex_lock(&vmbus_connection.channel_mutex);
 
-       init_vp_index(newchannel, hv_get_dev_type(newchannel));
+       init_vp_index(newchannel);
 
        /* Remember the channels that should be cleaned up upon suspend. */
        if (is_hvsock_channel(newchannel) || is_sub_channel(newchannel))
@@ -676,9 +683,9 @@ static int next_numa_node_id;
  * evenly among all the available NUMA nodes.  Once the node is assigned,
  * we will assign the CPU based on a simple round robin scheme.
  */
-static void init_vp_index(struct vmbus_channel *channel, u16 dev_type)
+static void init_vp_index(struct vmbus_channel *channel)
 {
-       bool perf_chn = vmbus_devs[dev_type].perf_device;
+       bool perf_chn = hv_is_perf_channel(channel);
        cpumask_var_t available_mask;
        struct cpumask *alloced_mask;
        u32 target_cpu;
@@ -699,6 +706,8 @@ static void init_vp_index(struct vmbus_channel *channel, u16 dev_type)
                channel->target_cpu = VMBUS_CONNECT_CPU;
                channel->target_vp =
                        hv_cpu_number_to_vp_number(VMBUS_CONNECT_CPU);
+               if (perf_chn)
+                       hv_set_alloced_cpu(VMBUS_CONNECT_CPU);
                return;
        }
 
@@ -862,6 +871,7 @@ static void vmbus_setup_channel_state(struct vmbus_channel *channel,
               sizeof(struct vmbus_channel_offer_channel));
        channel->monitor_grp = (u8)offer->monitorid / 32;
        channel->monitor_bit = (u8)offer->monitorid % 32;
+       channel->device_id = hv_get_dev_type(channel);
 }
 
 /*

diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 5e5cebe..40e2b9f 100644 (file)
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -395,6 +395,54 @@ enum delay {
        MESSAGE_DELAY   = 1,
 };
 
+extern const struct vmbus_device vmbus_devs[];
+
+static inline bool hv_is_perf_channel(struct vmbus_channel *channel)
+{
+       return vmbus_devs[channel->device_id].perf_device;
+}
+
+static inline bool hv_is_alloced_cpu(unsigned int cpu)
+{
+       struct vmbus_channel *channel, *sc;
+
+       lockdep_assert_held(&vmbus_connection.channel_mutex);
+       /*
+        * List additions/deletions as well as updates of the target CPUs are
+        * protected by channel_mutex.
+        */
+       list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
+               if (!hv_is_perf_channel(channel))
+                       continue;
+               if (channel->target_cpu == cpu)
+                       return true;
+               list_for_each_entry(sc, &channel->sc_list, sc_list) {
+                       if (sc->target_cpu == cpu)
+                               return true;
+               }
+       }
+       return false;
+}
+
+static inline void hv_set_alloced_cpu(unsigned int cpu)
+{
+       cpumask_set_cpu(cpu, &hv_context.hv_numa_map[cpu_to_node(cpu)]);
+}
+
+static inline void hv_clear_alloced_cpu(unsigned int cpu)
+{
+       if (hv_is_alloced_cpu(cpu))
+               return;
+       cpumask_clear_cpu(cpu, &hv_context.hv_numa_map[cpu_to_node(cpu)]);
+}
+
+static inline void hv_update_alloced_cpus(unsigned int old_cpu,
+                                         unsigned int new_cpu)
+{
+       hv_set_alloced_cpu(new_cpu);
+       hv_clear_alloced_cpu(old_cpu);
+}
+
 #ifdef CONFIG_HYPERV_TESTING
 
 int hv_debug_add_dev_dir(struct hv_device *dev);

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index c2a4a7c..4774775 100644 (file)
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1687,8 +1687,8 @@ static ssize_t target_cpu_show(struct vmbus_channel *channel, char *buf)
 static ssize_t target_cpu_store(struct vmbus_channel *channel,
                                const char *buf, size_t count)
 {
+       u32 target_cpu, origin_cpu;
        ssize_t ret = count;
-       u32 target_cpu;
 
        if (vmbus_proto_version < VERSION_WIN10_V4_1)
                return -EIO;
@@ -1741,7 +1741,8 @@ static ssize_t target_cpu_store(struct vmbus_channel *channel,
                goto cpu_store_unlock;
        }
 
-       if (channel->target_cpu == target_cpu)
+       origin_cpu = channel->target_cpu;
+       if (target_cpu == origin_cpu)
                goto cpu_store_unlock;
 
        if (vmbus_send_modifychannel(channel->offermsg.child_relid,
@@ -1763,14 +1764,20 @@ static ssize_t target_cpu_store(struct vmbus_channel *channel,
         * in on a CPU that is different from the channel target_cpu value.
         */
 
-       if (channel->change_target_cpu_callback)
-               (*channel->change_target_cpu_callback)(channel,
-                               channel->target_cpu, target_cpu);
-
        channel->target_cpu = target_cpu;
        channel->target_vp = hv_cpu_number_to_vp_number(target_cpu);
        channel->numa_node = cpu_to_node(target_cpu);
 
+       /* See init_vp_index(). */
+       if (hv_is_perf_channel(channel))
+               hv_update_alloced_cpus(origin_cpu, target_cpu);
+
+       /* Currently set only for storvsc channels. */
+       if (channel->change_target_cpu_callback) {
+               (*channel->change_target_cpu_callback)(channel,
+                               origin_cpu, target_cpu);
+       }
+
 cpu_store_unlock:
        mutex_unlock(&vmbus_connection.channel_mutex);
        cpus_read_unlock();

diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index d783847..40df310 100644 (file)
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -902,6 +902,13 @@ struct vmbus_channel {
        bool probe_done;
 
        /*
+        * Cache the device ID here for easy access; this is useful, in
+        * particular, in situations where the channel's device_obj has
+        * not been allocated/initialized yet.
+        */
+       u16 device_id;
+
+       /*
         * We must offload the handling of the primary/sub channels
         * from the single-threaded vmbus_connection.work_queue to
         * two different workqueue, otherwise we can block