From 3ce424e45411cf5a13105e0386b6ecf6eeb4f66f Mon Sep 17 00:00:00 2001 From: Roman Kagan Date: Wed, 18 May 2016 17:48:20 +0300 Subject: [PATCH] kvm:vmx: more complete state update on APICv on/off The function to update APICv on/off state (in particular, to deactivate it when enabling Hyper-V SynIC) is incomplete: it doesn't adjust APICv-related fields among secondary processor-based VM-execution controls. As a result, Windows 2012 guests get stuck when SynIC-based auto-EOI interrupt intersected with e.g. an IPI in the guest. In addition, the MSR intercept bitmap isn't updated every time "virtualize x2APIC mode" is toggled. This path can only be triggered by a malicious guest, because Windows didn't use x2APIC but rather their own synthetic APIC access MSRs; however a guest running in a SynIC-enabled VM could switch to x2APIC and thus obtain direct access to host APIC MSRs (CVE-2016-4440). The patch fixes those omissions. Signed-off-by: Roman Kagan Reported-by: Steve Rutherford Reported-by: Yang Zhang Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx.c | 48 +++++++++++++++++++++++++++++----------------- 1 file changed, 30 insertions(+), 18 deletions(-) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 7ebf27bafe5c..378a23ab6093 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -2418,7 +2418,9 @@ static void vmx_set_msr_bitmap(struct kvm_vcpu *vcpu) if (is_guest_mode(vcpu)) msr_bitmap = vmx_msr_bitmap_nested; - else if (vcpu->arch.apic_base & X2APIC_ENABLE) { + else if (cpu_has_secondary_exec_ctrls() && + (vmcs_read32(SECONDARY_VM_EXEC_CONTROL) & + SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE)) { if (is_long_mode(vcpu)) msr_bitmap = vmx_msr_bitmap_longmode_x2apic; else @@ -4783,6 +4785,19 @@ static void vmx_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu) struct vcpu_vmx *vmx = to_vmx(vcpu); vmcs_write32(PIN_BASED_VM_EXEC_CONTROL, vmx_pin_based_exec_ctrl(vmx)); + if (cpu_has_secondary_exec_ctrls()) { + if (kvm_vcpu_apicv_active(vcpu)) + vmcs_set_bits(SECONDARY_VM_EXEC_CONTROL, + SECONDARY_EXEC_APIC_REGISTER_VIRT | + SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY); + else + vmcs_clear_bits(SECONDARY_VM_EXEC_CONTROL, + SECONDARY_EXEC_APIC_REGISTER_VIRT | + SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY); + } + + if (cpu_has_vmx_msr_bitmap()) + vmx_set_msr_bitmap(vcpu); } static u32 vmx_exec_control(struct vcpu_vmx *vmx) @@ -6329,23 +6344,20 @@ static __init int hardware_setup(void) set_bit(0, vmx_vpid_bitmap); /* 0 is reserved for host */ - if (enable_apicv) { - for (msr = 0x800; msr <= 0x8ff; msr++) - vmx_disable_intercept_msr_read_x2apic(msr); - - /* According SDM, in x2apic mode, the whole id reg is used. - * But in KVM, it only use the highest eight bits. Need to - * intercept it */ - vmx_enable_intercept_msr_read_x2apic(0x802); - /* TMCCT */ - vmx_enable_intercept_msr_read_x2apic(0x839); - /* TPR */ - vmx_disable_intercept_msr_write_x2apic(0x808); - /* EOI */ - vmx_disable_intercept_msr_write_x2apic(0x80b); - /* SELF-IPI */ - vmx_disable_intercept_msr_write_x2apic(0x83f); - } + for (msr = 0x800; msr <= 0x8ff; msr++) + vmx_disable_intercept_msr_read_x2apic(msr); + + /* According SDM, in x2apic mode, the whole id reg is used. But in + * KVM, it only use the highest eight bits. Need to intercept it */ + vmx_enable_intercept_msr_read_x2apic(0x802); + /* TMCCT */ + vmx_enable_intercept_msr_read_x2apic(0x839); + /* TPR */ + vmx_disable_intercept_msr_write_x2apic(0x808); + /* EOI */ + vmx_disable_intercept_msr_write_x2apic(0x80b); + /* SELF-IPI */ + vmx_disable_intercept_msr_write_x2apic(0x83f); if (enable_ept) { kvm_mmu_set_mask_ptes(0ull, -- 2.20.1