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Drivers: hv: vmbus: Synchronize init_vp_index() vs. CPU hotplug

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init_vp_index() may access the cpu_online_mask mask via its calls of
cpumask_of_node().  Make sure to protect these accesses with a
cpus_read_lock() critical section.

Also, remove some (hardcoded) instances of CPU(0) from init_vp_index()
and replace them with VMBUS_CONNECT_CPU.  The connect CPU can not go
offline, since Hyper-V does not provide a way to change it.

Finally, order the accesses of target_cpu from init_vp_index() and
hv_synic_cleanup() by relying on the channel_mutex; this is achieved
by moving the call of init_vp_index() into vmbus_process_offer().

Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
Link: https://lore.kernel.org/r/20200406001514.19876-10-parri.andrea@gmail.com
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
This commit is contained in:
Andrea Parri (Microsoft) 2020-04-06 02:15:12 +02:00 committed by Wei Liu
parent 8ef4c4abbb
commit d570aec0f2
2 changed files with 38 additions and 16 deletions
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47
drivers/hv/channel_mgmt.c
View file

@ -18,6 +18,7 @@
#include <linux/module.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/cpu.h>
#include <linux/hyperv.h>
#include <asm/mshyperv.h>
@ -466,13 +467,8 @@ static void vmbus_add_channel_work(struct work_struct *work)
container_of(work, struct vmbus_channel, add_channel_work);
struct vmbus_channel *primary_channel = newchannel->primary_channel;
unsigned long flags;
u16 dev_type;
int ret;
dev_type = hv_get_dev_type(newchannel);
init_vp_index(newchannel, dev_type);
/*
* This state is used to indicate a successful open
* so that when we do close the channel normally, we
@ -504,7 +500,7 @@ static void vmbus_add_channel_work(struct work_struct *work)
if (!newchannel->device_obj)
goto err_deq_chan;
newchannel->device_obj->device_id = dev_type;
newchannel->device_obj->device_id = hv_get_dev_type(newchannel);
/*
* Add the new device to the bus. This will kick off device-driver
* binding which eventually invokes the device driver's AddDevice()
@ -560,6 +556,25 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel)
unsigned long flags;
bool fnew = true;
/*
* Initialize the target_CPU before inserting the channel in
* the chn_list and sc_list lists, within the channel_mutex
* critical section:
*
* CPU1 CPU2
*
* [vmbus_process_offer()] [hv_syninc_cleanup()]
*
* STORE target_cpu LOCK channel_mutex
* LOCK channel_mutex SEARCH chn_list
* INSERT chn_list LOAD target_cpu
* UNLOCK channel_mutex UNLOCK channel_mutex
*
* Forbids: CPU2's SEARCH from seeing CPU1's INSERT &&
* CPU2's LOAD from *not* seing CPU1's STORE
*/
init_vp_index(newchannel, hv_get_dev_type(newchannel));
mutex_lock(&vmbus_connection.channel_mutex);
/* Remember the channels that should be cleaned up upon suspend. */
@ -656,7 +671,7 @@ static DEFINE_SPINLOCK(bind_channel_to_cpu_lock);
* channel interrupt load by binding a channel to VCPU.
*
* For pre-win8 hosts or non-performance critical channels we assign the
* first CPU in the first NUMA node.
* VMBUS_CONNECT_CPU.
*
* Starting with win8, performance critical channels will be distributed
* evenly among all the available NUMA nodes. Once the node is assigned,
@ -675,17 +690,22 @@ static void init_vp_index(struct vmbus_channel *channel, u16 dev_type)
!alloc_cpumask_var(&available_mask, GFP_KERNEL)) {
/*
* Prior to win8, all channel interrupts are
* delivered on cpu 0.
* delivered on VMBUS_CONNECT_CPU.
* Also if the channel is not a performance critical
* channel, bind it to cpu 0.
* In case alloc_cpumask_var() fails, bind it to cpu 0.
* channel, bind it to VMBUS_CONNECT_CPU.
* In case alloc_cpumask_var() fails, bind it to
* VMBUS_CONNECT_CPU.
*/
channel->numa_node = 0;
channel->target_cpu = 0;
channel->target_vp = hv_cpu_number_to_vp_number(0);
channel->numa_node = cpu_to_node(VMBUS_CONNECT_CPU);
channel->target_cpu = VMBUS_CONNECT_CPU;
channel->target_vp =
hv_cpu_number_to_vp_number(VMBUS_CONNECT_CPU);
return;
}
/* No CPUs can come up or down during this. */
cpus_read_lock();
/*
* Serializes the accesses to the global variable next_numa_node_id.
* See also the header comment of the spin lock declaration.
@ -723,6 +743,7 @@ static void init_vp_index(struct vmbus_channel *channel, u16 dev_type)
channel->target_vp = hv_cpu_number_to_vp_number(target_cpu);
spin_unlock(&bind_channel_to_cpu_lock);
cpus_read_unlock();
free_cpumask_var(available_mask);
}

7
drivers/hv/hv.c
View file

@ -256,9 +256,10 @@ int hv_synic_cleanup(unsigned int cpu)
/*
* Search for channels which are bound to the CPU we're about to
* cleanup. In case we find one and vmbus is still connected we need to
* fail, this will effectively prevent CPU offlining. There is no way
* we can re-bind channels to different CPUs for now.
* cleanup. In case we find one and vmbus is still connected, we
* fail; this will effectively prevent CPU offlining.
*
* TODO: Re-bind the channels to different CPUs.
*/
mutex_lock(&vmbus_connection.channel_mutex);
list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {