Commit b635ccc1 authored by Andrea Parri (Microsoft)'s avatar Andrea Parri (Microsoft) Committed by Wei Liu
Browse files

Drivers: hv: vmbus: Check for pending channel interrupts before taking a CPU offline 



Check that enough time has passed such that the modify channel message
has been processed before taking a CPU offline.

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/20210416143449.16185-4-parri.andrea@gmail.com


Signed-off-by: default avatarWei Liu <wei.liu@kernel.org>
parent 870ced05

drivers/hv/hv.c

+53 −3
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#include <linux/hyperv.h>

#include <linux/random.h>

#include <linux/clockchips.h>

#include <linux/delay.h>

#include <linux/interrupt.h>

#include <clocksource/hyperv_timer.h>

#include <asm/mshyperv.h>
@@ -292,12 +293,50 @@ void hv_synic_disable_regs(unsigned int cpu) 
		disable_percpu_irq(vmbus_irq);

}



#define HV_MAX_TRIES 3

/*

 * Scan the event flags page of 'this' CPU looking for any bit that is set.  If we find one

 * bit set, then wait for a few milliseconds.  Repeat these steps for a maximum of 3 times.

 * Return 'true', if there is still any set bit after this operation; 'false', otherwise.

 *

 * If a bit is set, that means there is a pending channel interrupt.  The expectation is

 * that the normal interrupt handling mechanism will find and process the channel interrupt

 * "very soon", and in the process clear the bit.

 */

static bool hv_synic_event_pending(void)

{

	struct hv_per_cpu_context *hv_cpu = this_cpu_ptr(hv_context.cpu_context);

	union hv_synic_event_flags *event =

		(union hv_synic_event_flags *)hv_cpu->synic_event_page + VMBUS_MESSAGE_SINT;

	unsigned long *recv_int_page = event->flags; /* assumes VMBus version >= VERSION_WIN8 */

	bool pending;

	u32 relid;

	int tries = 0;



retry:

	pending = false;

	for_each_set_bit(relid, recv_int_page, HV_EVENT_FLAGS_COUNT) {

		/* Special case - VMBus channel protocol messages */

		if (relid == 0)

			continue;

		pending = true;

		break;

	}

	if (pending && tries++ < HV_MAX_TRIES) {

		usleep_range(10000, 20000);

		goto retry;

	}

	return pending;

}



int hv_synic_cleanup(unsigned int cpu)

{

	struct vmbus_channel *channel, *sc;

	bool channel_found = false;



	if (vmbus_connection.conn_state != CONNECTED)

		goto always_cleanup;



	/*

	 * Hyper-V does not provide a way to change the connect CPU once

	 * it is set; we must prevent the connect CPU from going offline
@@ -305,8 +344,7 @@ int hv_synic_cleanup(unsigned int cpu) 
	 * path where the vmbus is already disconnected, the CPU must be

	 * allowed to shut down.

	 */

	if (cpu == VMBUS_CONNECT_CPU &&

	    vmbus_connection.conn_state == CONNECTED)

	if (cpu == VMBUS_CONNECT_CPU)

		return -EBUSY;



	/*
@@ -333,9 +371,21 @@ int hv_synic_cleanup(unsigned int cpu) 
	}

	mutex_unlock(&vmbus_connection.channel_mutex);



	if (channel_found && vmbus_connection.conn_state == CONNECTED)

	if (channel_found)

		return -EBUSY;



	/*

	 * channel_found == false means that any channels that were previously

	 * assigned to the CPU have been reassigned elsewhere with a call of

	 * vmbus_send_modifychannel().  Scan the event flags page looking for

	 * bits that are set and waiting with a timeout for vmbus_chan_sched()

	 * to process such bits.  If bits are still set after this operation

	 * and VMBus is connected, fail the CPU offlining operation.

	 */

	if (vmbus_proto_version >= VERSION_WIN10_V4_1 && hv_synic_event_pending())

		return -EBUSY;



always_cleanup:

	hv_stimer_legacy_cleanup(cpu);



	hv_synic_disable_regs(cpu);