Commit afaa33da authored by Andrea Parri (Microsoft)'s avatar Andrea Parri (Microsoft) Committed by Wei Liu
Browse files

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: 75278105 ("Drivers: hv: vmbus: Introduce the CHANNELMSG_MODIFYCHANNEL message type")
Signed-off-by: default avatarAndrea Parri (Microsoft) <parri.andrea@gmail.com>
Reviewed-by: default avatarMichael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20200522171901.204127-3-parri.andrea@gmail.com


Signed-off-by: default avatarWei Liu <wei.liu@kernel.org>
parent a949e86c

drivers/hv/channel_mgmt.c

+16 −6
Original line number Diff line number Diff line
@@ -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,
@@ -431,6 +431,13 @@ void hv_process_channel_removal(struct vmbus_channel *channel) 
		spin_unlock_irqrestore(&primary_channel->lock, flags);

	}



	/*

	 * 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
@@ -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);

}



/*

drivers/hv/hyperv_vmbus.h

+48 −0
Original line number Diff line number Diff line
@@ -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);

drivers/hv/vmbus_drv.c

+13 −6
Original line number Diff line number Diff line
@@ -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();

include/linux/hyperv.h

+7 −0
Original line number Diff line number Diff line
@@ -901,6 +901,13 @@ 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

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