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Drivers: hv: vmbus: Remove the unused HV_LOCALIZED channel affinity l…
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…ogic

The logic is unused since commit 509879b ("Drivers: hv: Introduce
a policy for controlling channel affinity").

This logic assumes that a channel target_cpu doesn't change during the
lifetime of a channel, but this assumption is incompatible with the new
functionality that allows changing the vCPU a channel will interrupt.

Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
Link: https://lore.kernel.org/r/20200406001514.19876-9-parri.andrea@gmail.com
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
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Andrea Parri (Microsoft) authored and Wei Liu committed Apr 23, 2020
1 parent 240ad77 commit 8ef4c4a
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Showing 2 changed files with 25 additions and 107 deletions.
105 changes: 25 additions & 80 deletions drivers/hv/channel_mgmt.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -433,14 +433,6 @@ void hv_process_channel_removal(struct vmbus_channel *channel)
spin_unlock_irqrestore(&primary_channel->lock, flags);
}

/*
* We need to free the bit for init_vp_index() to work in the case
* of sub-channel, when we reload drivers like hv_netvsc.
*/
if (channel->affinity_policy == HV_LOCALIZED)
cpumask_clear_cpu(channel->target_cpu,
&primary_channel->alloced_cpus_in_node);

/*
* Upon suspend, an in-use hv_sock channel is marked as "rescinded" and
* the relid is invalidated; after hibernation, when the user-space app
Expand Down Expand Up @@ -662,20 +654,21 @@ static DEFINE_SPINLOCK(bind_channel_to_cpu_lock);
/*
* Starting with Win8, we can statically distribute the incoming
* channel interrupt load by binding a channel to VCPU.
* We distribute the interrupt loads to one or more NUMA nodes based on
* the channel's affinity_policy.
*
* For pre-win8 hosts or non-performance critical channels we assign the
* first CPU in the first NUMA node.
*
* Starting with win8, performance critical channels will be distributed
* 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)
{
u32 cur_cpu;
bool perf_chn = vmbus_devs[dev_type].perf_device;
struct vmbus_channel *primary = channel->primary_channel;
int next_node;
cpumask_var_t available_mask;
struct cpumask *alloced_mask;
u32 target_cpu;
int numa_node;

if ((vmbus_proto_version == VERSION_WS2008) ||
(vmbus_proto_version == VERSION_WIN7) || (!perf_chn) ||
Expand All @@ -693,89 +686,41 @@ static void init_vp_index(struct vmbus_channel *channel, u16 dev_type)
return;
}

spin_lock(&bind_channel_to_cpu_lock);

/*
* Based on the channel affinity policy, we will assign the NUMA
* nodes.
* Serializes the accesses to the global variable next_numa_node_id.
* See also the header comment of the spin lock declaration.
*/
spin_lock(&bind_channel_to_cpu_lock);

if ((channel->affinity_policy == HV_BALANCED) || (!primary)) {
while (true) {
next_node = next_numa_node_id++;
if (next_node == nr_node_ids) {
next_node = next_numa_node_id = 0;
continue;
}
if (cpumask_empty(cpumask_of_node(next_node)))
continue;
break;
while (true) {
numa_node = next_numa_node_id++;
if (numa_node == nr_node_ids) {
next_numa_node_id = 0;
continue;
}
channel->numa_node = next_node;
primary = channel;
if (cpumask_empty(cpumask_of_node(numa_node)))
continue;
break;
}
alloced_mask = &hv_context.hv_numa_map[primary->numa_node];
channel->numa_node = numa_node;
alloced_mask = &hv_context.hv_numa_map[numa_node];

if (cpumask_weight(alloced_mask) ==
cpumask_weight(cpumask_of_node(primary->numa_node))) {
cpumask_weight(cpumask_of_node(numa_node))) {
/*
* We have cycled through all the CPUs in the node;
* reset the alloced map.
*/
cpumask_clear(alloced_mask);
}

cpumask_xor(available_mask, alloced_mask,
cpumask_of_node(primary->numa_node));
cpumask_xor(available_mask, alloced_mask, cpumask_of_node(numa_node));

cur_cpu = -1;

if (primary->affinity_policy == HV_LOCALIZED) {
/*
* Normally Hyper-V host doesn't create more subchannels
* than there are VCPUs on the node but it is possible when not
* all present VCPUs on the node are initialized by guest.
* Clear the alloced_cpus_in_node to start over.
*/
if (cpumask_equal(&primary->alloced_cpus_in_node,
cpumask_of_node(primary->numa_node)))
cpumask_clear(&primary->alloced_cpus_in_node);
}

while (true) {
cur_cpu = cpumask_next(cur_cpu, available_mask);
if (cur_cpu >= nr_cpu_ids) {
cur_cpu = -1;
cpumask_copy(available_mask,
cpumask_of_node(primary->numa_node));
continue;
}

if (primary->affinity_policy == HV_LOCALIZED) {
/*
* NOTE: in the case of sub-channel, we clear the
* sub-channel related bit(s) in
* primary->alloced_cpus_in_node in
* hv_process_channel_removal(), so when we
* reload drivers like hv_netvsc in SMP guest, here
* we're able to re-allocate
* bit from primary->alloced_cpus_in_node.
*/
if (!cpumask_test_cpu(cur_cpu,
&primary->alloced_cpus_in_node)) {
cpumask_set_cpu(cur_cpu,
&primary->alloced_cpus_in_node);
cpumask_set_cpu(cur_cpu, alloced_mask);
break;
}
} else {
cpumask_set_cpu(cur_cpu, alloced_mask);
break;
}
}
target_cpu = cpumask_first(available_mask);
cpumask_set_cpu(target_cpu, alloced_mask);

channel->target_cpu = cur_cpu;
channel->target_vp = hv_cpu_number_to_vp_number(cur_cpu);
channel->target_cpu = target_cpu;
channel->target_vp = hv_cpu_number_to_vp_number(target_cpu);

spin_unlock(&bind_channel_to_cpu_lock);

Expand Down
27 changes: 0 additions & 27 deletions include/linux/hyperv.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -689,11 +689,6 @@ union hv_connection_id {
} u;
};

enum hv_numa_policy {
HV_BALANCED = 0,
HV_LOCALIZED,
};

enum vmbus_device_type {
HV_IDE = 0,
HV_SCSI,
Expand Down Expand Up @@ -808,10 +803,6 @@ struct vmbus_channel {
u32 target_vp;
/* The corresponding CPUID in the guest */
u32 target_cpu;
/*
* State to manage the CPU affiliation of channels.
*/
struct cpumask alloced_cpus_in_node;
int numa_node;
/*
* Support for sub-channels. For high performance devices,
Expand Down Expand Up @@ -898,18 +889,6 @@ struct vmbus_channel {
*/
bool low_latency;

/*
* NUMA distribution policy:
* We support two policies:
* 1) Balanced: Here all performance critical channels are
* distributed evenly amongst all the NUMA nodes.
* This policy will be the default policy.
* 2) Localized: All channels of a given instance of a
* performance critical service will be assigned CPUs
* within a selected NUMA node.
*/
enum hv_numa_policy affinity_policy;

bool probe_done;

/*
Expand Down Expand Up @@ -965,12 +944,6 @@ static inline bool is_sub_channel(const struct vmbus_channel *c)
return c->offermsg.offer.sub_channel_index != 0;
}

static inline void set_channel_affinity_state(struct vmbus_channel *c,
enum hv_numa_policy policy)
{
c->affinity_policy = policy;
}

static inline void set_channel_read_mode(struct vmbus_channel *c,
enum hv_callback_mode mode)
{
Expand Down

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