In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Unconditionally recompute CR8 intercept on PPR update The TPR_THRESHOLD field in the VMCS is used by VMX to induce VM exits when the guest's virtual TPR falls under the specified threshold, allowing KVM to inject previously masked interrupts. KVM handles these VM exits in handle_tpr_below_threshold(). Commit eb90f3417a0c ("KVM: vmx: speed up TPR below threshold vmexits") optimized this function by calling apic_update_ppr() instead of raising KVM_REQ_EVENT. apic_update_ppr() then raises KVM_REQ_EVENT if there is a pending, deliverable interrupt. However, if there are no new interrupts pending, apic_update_ppr() does not issue the request. Thus, kvm_lapic_update_cr8_intercept() and vmx_update_cr8_intercept() are not called before VM entry, which results in a high, stale TPR_THRESHOLD. This is problematic due to the following sentence in 28.2.1.1 "VM-Execution Control Fields" in the SDM: The following check i...

A flaw was found in the Linux kernel's Kernel-based Virtual Machine (KVM) for x86 architectures. When the `apic_update_ppr()` function does not find a deliverable interrupt, it fails to recompute the CR8 intercept, leading to a stale Task Priority Register Threshold (TPR_THRESHOLD). This issue can cause a virtual machine (VM) entry failure with a hardware error (0x7) on older platforms or in nested virtualization environments that do not support virtual-interrupt delivery, such as Hyper-V.

In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Unconditionally recompute CR8 intercept on PPR update The TPR_THRESHOLD field in the VMCS is used by VMX to induce VM exits when the guest's virtual TPR falls under the specified threshold, allowing KVM to inject previously masked interrupts. KVM handles these VM exits in handle_tpr_below_threshold(). Commit eb90f3417a0c ("KVM: vmx: speed up TPR below threshold vmexits") optimized this function by calling apic_update_ppr() instead of raising KVM_REQ_EVENT. apic_update_ppr() then raises KVM_REQ_EVENT if there is a pending, deliverable interrupt. However, if there are no new interrupts pending, apic_update_ppr() does not issue the request. Thus, kvm_lapic_update_cr8_intercept() and vmx_update_cr8_intercept() are not called before VM entry, which results in a high, stale TPR_THRESHOLD. This is problematic due to the following sentence in 28.2.1.1 "VM-Execution Control Fields" in the SDM: The following che

KVM: x86: Unconditionally recompute CR8 intercept on PPR update

In the Linux kernel, the following vulnerability has been resolved: K ...

In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Unconditionally recompute CR8 intercept on PPR update The TPR_THRESHOLD field in the VMCS is used by VMX to induce VM exits when the guest's virtual TPR falls under the specified threshold, allowing KVM to inject previously masked interrupts. KVM handles these VM exits in handle_tpr_below_threshold(). Commit eb90f3417a0c ("KVM: vmx: speed up TPR below threshold vmexits") optimized this function by calling apic_update_ppr() instead of raising KVM_REQ_EVENT. apic_update_ppr() then raises KVM_REQ_EVENT if there is a pending, deliverable interrupt. However, if there are no new interrupts pending, apic_update_ppr() does not issue the request. Thus, kvm_lapic_update_cr8_intercept() and vmx_update_cr8_intercept() are not called before VM entry, which results in a high, stale TPR_THRESHOLD. This is problematic due to the following sentence in 28.2.1.1 "VM-Execution Control Fields" in the SDM: The following ...