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    Subject[PATCH 12/47] KVM: VMX: EPT misconfiguration handler
    Date
    From: Marcelo Tosatti <mtosatti@redhat.com>

    Handler for EPT misconfiguration which checks for valid state
    in the shadow pagetables, printing the spte on each level.

    The separate WARN_ONs are useful for kerneloops.org.

    Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
    Signed-off-by: Avi Kivity <avi@redhat.com>
    ---
    arch/x86/kvm/vmx.c | 86 +++++++++++++++++++++++++++++++++++++++++++++++++++-
    1 files changed, 85 insertions(+), 1 deletions(-)

    diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
    index 6610181..94c07ad 100644
    --- a/arch/x86/kvm/vmx.c
    +++ b/arch/x86/kvm/vmx.c
    @@ -3227,6 +3227,89 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
    return kvm_mmu_page_fault(vcpu, gpa & PAGE_MASK, 0);
    }

    +static u64 ept_rsvd_mask(u64 spte, int level)
    +{
    + int i;
    + u64 mask = 0;
    +
    + for (i = 51; i > boot_cpu_data.x86_phys_bits; i--)
    + mask |= (1ULL << i);
    +
    + if (level > 2)
    + /* bits 7:3 reserved */
    + mask |= 0xf8;
    + else if (level == 2) {
    + if (spte & (1ULL << 7))
    + /* 2MB ref, bits 20:12 reserved */
    + mask |= 0x1ff000;
    + else
    + /* bits 6:3 reserved */
    + mask |= 0x78;
    + }
    +
    + return mask;
    +}
    +
    +static void ept_misconfig_inspect_spte(struct kvm_vcpu *vcpu, u64 spte,
    + int level)
    +{
    + printk(KERN_ERR "%s: spte 0x%llx level %d\n", __func__, spte, level);
    +
    + /* 010b (write-only) */
    + WARN_ON((spte & 0x7) == 0x2);
    +
    + /* 110b (write/execute) */
    + WARN_ON((spte & 0x7) == 0x6);
    +
    + /* 100b (execute-only) and value not supported by logical processor */
    + if (!cpu_has_vmx_ept_execute_only())
    + WARN_ON((spte & 0x7) == 0x4);
    +
    + /* not 000b */
    + if ((spte & 0x7)) {
    + u64 rsvd_bits = spte & ept_rsvd_mask(spte, level);
    +
    + if (rsvd_bits != 0) {
    + printk(KERN_ERR "%s: rsvd_bits = 0x%llx\n",
    + __func__, rsvd_bits);
    + WARN_ON(1);
    + }
    +
    + if (level == 1 || (level == 2 && (spte & (1ULL << 7)))) {
    + u64 ept_mem_type = (spte & 0x38) >> 3;
    +
    + if (ept_mem_type == 2 || ept_mem_type == 3 ||
    + ept_mem_type == 7) {
    + printk(KERN_ERR "%s: ept_mem_type=0x%llx\n",
    + __func__, ept_mem_type);
    + WARN_ON(1);
    + }
    + }
    + }
    +}
    +
    +static int handle_ept_misconfig(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
    +{
    + u64 sptes[4];
    + int nr_sptes, i;
    + gpa_t gpa;
    +
    + gpa = vmcs_read64(GUEST_PHYSICAL_ADDRESS);
    +
    + printk(KERN_ERR "EPT: Misconfiguration.\n");
    + printk(KERN_ERR "EPT: GPA: 0x%llx\n", gpa);
    +
    + nr_sptes = kvm_mmu_get_spte_hierarchy(vcpu, gpa, sptes);
    +
    + for (i = PT64_ROOT_LEVEL; i > PT64_ROOT_LEVEL - nr_sptes; --i)
    + ept_misconfig_inspect_spte(vcpu, sptes[i-1], i);
    +
    + kvm_run->exit_reason = KVM_EXIT_UNKNOWN;
    + kvm_run->hw.hardware_exit_reason = EXIT_REASON_EPT_MISCONFIG;
    +
    + return 0;
    +}
    +
    static int handle_nmi_window(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
    {
    u32 cpu_based_vm_exec_control;
    @@ -3306,8 +3389,9 @@ static int (*kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu,
    [EXIT_REASON_APIC_ACCESS] = handle_apic_access,
    [EXIT_REASON_WBINVD] = handle_wbinvd,
    [EXIT_REASON_TASK_SWITCH] = handle_task_switch,
    - [EXIT_REASON_EPT_VIOLATION] = handle_ept_violation,
    [EXIT_REASON_MCE_DURING_VMENTRY] = handle_machine_check,
    + [EXIT_REASON_EPT_VIOLATION] = handle_ept_violation,
    + [EXIT_REASON_EPT_MISCONFIG] = handle_ept_misconfig,
    };

    static const int kvm_vmx_max_exit_handlers =
    --
    1.6.3.3


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