linux/virt/kvm
Marcelo Tosatti a2486020a8 KVM: VMX: update vcpu posted-interrupt descriptor when assigning device
For VMX, when a vcpu enters HLT emulation, pi_post_block will:

1) Add vcpu to per-cpu list of blocked vcpus.

2) Program the posted-interrupt descriptor "notification vector"
to POSTED_INTR_WAKEUP_VECTOR

With interrupt remapping, an interrupt will set the PIR bit for the
vector programmed for the device on the CPU, test-and-set the
ON bit on the posted interrupt descriptor, and if the ON bit is clear
generate an interrupt for the notification vector.

This way, the target CPU wakes upon a device interrupt and wakes up
the target vcpu.

Problem is that pi_post_block only programs the notification vector
if kvm_arch_has_assigned_device() is true. Its possible for the
following to happen:

1) vcpu V HLTs on pcpu P, kvm_arch_has_assigned_device is false,
notification vector is not programmed
2) device is assigned to VM
3) device interrupts vcpu V, sets ON bit
(notification vector not programmed, so pcpu P remains in idle)
4) vcpu 0 IPIs vcpu V (in guest), but since pi descriptor ON bit is set,
kvm_vcpu_kick is skipped
5) vcpu 0 busy spins on vcpu V's response for several seconds, until
RCU watchdog NMIs all vCPUs.

To fix this, use the start_assignment kvm_x86_ops callback to kick
vcpus out of the halt loop, so the notification vector is
properly reprogrammed to the wakeup vector.

Reported-by: Pei Zhang <pezhang@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Message-Id: <20210526172014.GA29007@fuller.cnet>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-05-27 07:58:23 -04:00
..
async_pf.c mm/gup: remove task_struct pointer for all gup code 2020-08-12 10:58:04 -07:00
async_pf.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 504 2019-06-19 17:09:56 +02:00
coalesced_mmio.c KVM: Stop looking for coalesced MMIO zones if the bus is destroyed 2021-04-20 04:18:51 -04:00
coalesced_mmio.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
dirty_ring.c KVM: x86/mmu: Use an rwlock for the x86 MMU 2021-02-04 05:27:43 -05:00
eventfd.c kvm/eventfd: Drain events from eventfd in irqfd_wakeup() 2020-11-15 09:49:11 -05:00
irqchip.c KVM/arm updates for 5.3 2019-07-11 15:14:16 +02:00
Kconfig entry: Provide infrastructure for work before transitioning to guest mode 2020-07-24 15:03:42 +02:00
kvm_main.c KVM: VMX: update vcpu posted-interrupt descriptor when assigning device 2021-05-27 07:58:23 -04:00
mmu_lock.h KVM: x86/mmu: Use an rwlock for the x86 MMU 2021-02-04 05:27:43 -05:00
vfio.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
vfio.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00