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

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

Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20210416143449.16185-4-parri.andrea@gmail.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
This commit is contained in:
Andrea Parri (Microsoft) 2021-04-16 16:34:49 +02:00 committed by Wei Liu
parent 870ced0548
commit b635ccc1ec
1 changed files with 53 additions and 3 deletions
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56
drivers/hv/hv.c
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@ -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);