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KVM: x86: Recompute PID.ON when clearing PID.SN

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Some Posted-Interrupts from passthrough devices may be lost or
overwritten when the vCPU is in runnable state.

The SN (Suppress Notification) of PID (Posted Interrupt Descriptor) will
be set when the vCPU is preempted (vCPU in KVM_MP_STATE_RUNNABLE state but
not running on physical CPU). If a posted interrupt comes at this time,
the irq remapping facility will set the bit of PIR (Posted Interrupt
Requests) but not ON (Outstanding Notification).  Then, the interrupt
will not be seen by KVM, which always expects PID.ON=1 if PID.PIR=1
as documented in the Intel processor SDM but not in the VT-d specification.
To fix this, restore the invariant after PID.SN is cleared.

Signed-off-by: Luwei Kang <luwei.kang@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Luwei Kang
2019-02-14 10:48:07 +08:00
committed by Paolo Bonzini
parent 08e16754ca
commit c112b5f502
3 changed files with 18 additions and 22 deletions
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arch/x86/kvm/x86.c
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@@ -7801,7 +7801,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
* 1) We should set ->mode before checking ->requests. Please see
* the comment in kvm_vcpu_exiting_guest_mode().
*
* 2) For APICv, we should set ->mode before checking PIR.ON. This
* 2) For APICv, we should set ->mode before checking PID.ON. This
* pairs with the memory barrier implicit in pi_test_and_set_on
* (see vmx_deliver_posted_interrupt).
*