summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorSean Christopherson <seanjc@google.com>2022-04-20 04:37:30 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2022-04-27 15:39:00 +0300
commit8b2da96904895cb9f82c64e8ee428ddb15d040da (patch)
tree1ee25fcb842b6c14fa7099ad2d62322c47231b95
parenta41b3243a6de82a6d22cc4c30d0167bfea36f7e0 (diff)
downloadlinux-8b2da96904895cb9f82c64e8ee428ddb15d040da.tar.xz
KVM: nVMX: Defer APICv updates while L2 is active until L1 is active
commit 7c69661e225cc484fbf44a0b99b56714a5241ae3 upstream. Defer APICv updates that occur while L2 is active until nested VM-Exit, i.e. until L1 regains control. vmx_refresh_apicv_exec_ctrl() assumes L1 is active and (a) stomps all over vmcs02 and (b) neglects to ever updated vmcs01. E.g. if vmcs12 doesn't enable the TPR shadow for L2 (and thus no APICv controls), L1 performs nested VM-Enter APICv inhibited, and APICv becomes unhibited while L2 is active, KVM will set various APICv controls in vmcs02 and trigger a failed VM-Entry. The kicker is that, unless running with nested_early_check=1, KVM blames L1 and chaos ensues. In all cases, ignoring vmcs02 and always deferring the inhibition change to vmcs01 is correct (or at least acceptable). The ABSENT and DISABLE inhibitions cannot truly change while L2 is active (see below). IRQ_BLOCKING can change, but it is firmly a best effort debug feature. Furthermore, only L2's APIC is accelerated/virtualized to the full extent possible, e.g. even if L1 passes through its APIC to L2, normal MMIO/MSR interception will apply to the virtual APIC managed by KVM. The exception is the SELF_IPI register when x2APIC is enabled, but that's an acceptable hole. Lastly, Hyper-V's Auto EOI can technically be toggled if L1 exposes the MSRs to L2, but for that to work in any sane capacity, L1 would need to pass through IRQs to L2 as well, and IRQs must be intercepted to enable virtual interrupt delivery. I.e. exposing Auto EOI to L2 and enabling VID for L2 are, for all intents and purposes, mutually exclusive. Lack of dynamic toggling is also why this scenario is all but impossible to encounter in KVM's current form. But a future patch will pend an APICv update request _during_ vCPU creation to plug a race where a vCPU that's being created doesn't get included in the "all vCPUs request" because it's not yet visible to other vCPUs. If userspaces restores L2 after VM creation (hello, KVM selftests), the first KVM_RUN will occur while L2 is active and thus service the APICv update request made during VM creation. Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20220420013732.3308816-3-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/x86/kvm/vmx/nested.c5
-rw-r--r--arch/x86/kvm/vmx/vmx.c5
-rw-r--r--arch/x86/kvm/vmx/vmx.h1
3 files changed, 11 insertions, 0 deletions
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index a0193b11c381..1546a10ecb56 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4601,6 +4601,11 @@ void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason,
kvm_make_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu);
}
+ if (vmx->nested.update_vmcs01_apicv_status) {
+ vmx->nested.update_vmcs01_apicv_status = false;
+ kvm_make_request(KVM_REQ_APICV_UPDATE, vcpu);
+ }
+
if ((vm_exit_reason != -1) &&
(enable_shadow_vmcs || evmptr_is_valid(vmx->nested.hv_evmcs_vmptr)))
vmx->nested.need_vmcs12_to_shadow_sync = true;
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 322485ab9271..16a660a0ed5f 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4098,6 +4098,11 @@ static void vmx_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
+ if (is_guest_mode(vcpu)) {
+ vmx->nested.update_vmcs01_apicv_status = true;
+ return;
+ }
+
pin_controls_set(vmx, vmx_pin_based_exec_ctrl(vmx));
if (cpu_has_secondary_exec_ctrls()) {
if (kvm_vcpu_apicv_active(vcpu))
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 3f9c8548625d..460c7bd8158c 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -164,6 +164,7 @@ struct nested_vmx {
bool change_vmcs01_virtual_apic_mode;
bool reload_vmcs01_apic_access_page;
bool update_vmcs01_cpu_dirty_logging;
+ bool update_vmcs01_apicv_status;
/*
* Enlightened VMCS has been enabled. It does not mean that L1 has to