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author | 2021-10-08 19:12:17 -0700 | |
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committer | 2021-12-08 04:24:56 -0500 | |
commit | 29802380b6793eabcac648e1c097c7bd6333f3d4 (patch) | |
tree | 2a26904bb189ac6d3f119873e493792f38c4c06b /arch/x86/kvm/vmx/posted_intr.c | |
parent | KVM: VMX: Use boolean returns for Posted Interrupt "test" helpers (diff) | |
download | wireguard-linux-29802380b6793eabcac648e1c097c7bd6333f3d4.tar.xz wireguard-linux-29802380b6793eabcac648e1c097c7bd6333f3d4.zip |
KVM: VMX: Drop pointless PI.NDST update when blocking
Don't update Posted Interrupt's NDST, a.k.a. the target pCPU, in the
pre-block path, as NDST is guaranteed to be up-to-date. The comment
about the vCPU being preempted during the update is simply wrong, as the
update path runs with IRQs disabled (from before snapshotting vcpu->cpu,
until after the update completes).
Since commit 8b306e2f3c41 ("KVM: VMX: avoid double list add with VT-d
posted interrupts", 2017-09-27) The vCPU can get preempted _before_
the update starts, but not during. And if the vCPU is preempted before,
vmx_vcpu_pi_load() is responsible for updating NDST when the vCPU is
scheduled back in. In that case, the check against the wakeup vector in
vmx_vcpu_pi_load() cannot be true as that would require the notification
vector to have been set to the wakeup vector _before_ blocking.
Opportunistically switch to using vcpu->cpu for the list/lock lookups,
which do not need pre_pcpu since the same commit.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211009021236.4122790-25-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/vmx/posted_intr.c')
-rw-r--r-- | arch/x86/kvm/vmx/posted_intr.c | 23 |
1 files changed, 3 insertions, 20 deletions
diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c index 8abd5d891bde..bb93e9637494 100644 --- a/arch/x86/kvm/vmx/posted_intr.c +++ b/arch/x86/kvm/vmx/posted_intr.c @@ -135,7 +135,6 @@ static void __pi_post_block(struct kvm_vcpu *vcpu) * - Store the vCPU to the wakeup list, so when interrupts happen * we can find the right vCPU to wake up. * - Change the Posted-interrupt descriptor as below: - * 'NDST' <-- vcpu->pre_pcpu * 'NV' <-- POSTED_INTR_WAKEUP_VECTOR * - If 'ON' is set during this process, which means at least one * interrupt is posted for this vCPU, we cannot block it, in @@ -144,7 +143,6 @@ static void __pi_post_block(struct kvm_vcpu *vcpu) */ int pi_pre_block(struct kvm_vcpu *vcpu) { - unsigned int dest; struct pi_desc old, new; struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu); @@ -156,10 +154,10 @@ int pi_pre_block(struct kvm_vcpu *vcpu) local_irq_disable(); vcpu->pre_pcpu = vcpu->cpu; - spin_lock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu)); + spin_lock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->cpu)); list_add_tail(&vcpu->blocked_vcpu_list, - &per_cpu(blocked_vcpu_on_cpu, vcpu->pre_pcpu)); - spin_unlock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu)); + &per_cpu(blocked_vcpu_on_cpu, vcpu->cpu)); + spin_unlock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->cpu)); do { old.control = new.control = pi_desc->control; @@ -168,21 +166,6 @@ int pi_pre_block(struct kvm_vcpu *vcpu) "Warning: SN field of posted-interrupts " "is set before blocking\n"); - /* - * Since vCPU can be preempted during this process, - * vcpu->cpu could be different with pre_pcpu, we - * need to set pre_pcpu as the destination of wakeup - * notification event, then we can find the right vCPU - * to wakeup in wakeup handler if interrupts happen - * when the vCPU is in blocked state. - */ - dest = cpu_physical_id(vcpu->pre_pcpu); - - if (x2apic_mode) - new.ndst = dest; - else - new.ndst = (dest << 8) & 0xFF00; - /* set 'NV' to 'wakeup vector' */ new.nv = POSTED_INTR_WAKEUP_VECTOR; } while (cmpxchg64(&pi_desc->control, old.control, |