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SubjectRe: [PATCH v2] KVM: x86: Sync the pending Posted-Interrupts
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On 30/01/19 01:59, Luwei Kang wrote:
> 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 coming at this
> time, the irq remmaping facility will set the bit of PIR (Posted
> Interrupt Requests) without ON (Outstanding Notification).
> So this interrupt can't be sync to APIC virtualization register and
> will not be handled by Guest because ON is zero.
>
> Signed-off-by: Luwei Kang <luwei.kang@intel.com>
> ---
> arch/x86/kvm/vmx/vmx.c | 2 +-
> arch/x86/kvm/x86.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index f6915f1..820a03b 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -6048,7 +6048,7 @@ static int vmx_sync_pir_to_irr(struct kvm_vcpu *vcpu)
> bool max_irr_updated;
>
> WARN_ON(!vcpu->arch.apicv_active);
> - if (pi_test_on(&vmx->pi_desc)) {
> + if (!bitmap_empty((unsigned long *)vmx->pi_desc.pir, NR_VECTORS)) {
> pi_clear_on(&vmx->pi_desc);
> /*
> * IOMMU can write to PIR.ON, so the barrier matters even on UP.

This is not what I asked. You should instead do the check after
pi_clear_sn.

Paolo

> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 02c8e09..c31b608 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7793,7 +7793,7 @@ 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.PIR. This
> * pairs with the memory barrier implicit in pi_test_and_set_on
> * (see vmx_deliver_posted_interrupt).
> *
>

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