From 06dad664d4eae136e8dfa9eea955b154213f3f2e Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 10 Aug 2021 07:45:26 -0700 Subject: [PATCH] KVM: nVMX: Unconditionally clear nested.pi_pending on nested VM-Enter commit f7782bb8d818d8f47c26b22079db10599922787a upstream. Clear nested.pi_pending on nested VM-Enter even if L2 will run without posted interrupts enabled. If nested.pi_pending is left set from a previous L2, vmx_complete_nested_posted_interrupt() will pick up the stale flag and exit to userspace with an "internal emulation error" due the new L2 not having a valid nested.pi_desc. Arguably, vmx_complete_nested_posted_interrupt() should first check for posted interrupts being enabled, but it's also completely reasonable that KVM wouldn't screw up a fundamental flag. Not to mention that the mere existence of nested.pi_pending is a long-standing bug as KVM shouldn't move the posted interrupt out of the IRR until it's actually processed, e.g. KVM effectively drops an interrupt when it performs a nested VM-Exit with a "pending" posted interrupt. Fixing the mess is a future problem. Prior to vmx_complete_nested_posted_interrupt() interpreting a null PI descriptor as an error, this was a benign bug as the null PI descriptor effectively served as a check on PI not being enabled. Even then, the new flow did not become problematic until KVM started checking the result of kvm_check_nested_events(). Fixes: 705699a13994 ("KVM: nVMX: Enable nested posted interrupt processing") Fixes: 966eefb89657 ("KVM: nVMX: Disable vmcs02 posted interrupts if vmcs12 PID isn't mappable") Fixes: 47d3530f86c0 ("KVM: x86: Exit to userspace when kvm_check_nested_events fails") Cc: stable@vger.kernel.org Cc: Jim Mattson Signed-off-by: Sean Christopherson Message-Id: <20210810144526.2662272-1-seanjc@google.com> Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/vmx/nested.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 023bd3e1aa0d..3041015b05f7 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -2057,12 +2057,11 @@ static void prepare_vmcs02_early(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12) ~PIN_BASED_VMX_PREEMPTION_TIMER); /* Posted interrupts setting is only taken from vmcs12. */ - if (nested_cpu_has_posted_intr(vmcs12)) { + vmx->nested.pi_pending = false; + if (nested_cpu_has_posted_intr(vmcs12)) vmx->nested.posted_intr_nv = vmcs12->posted_intr_nv; - vmx->nested.pi_pending = false; - } else { + else exec_control &= ~PIN_BASED_POSTED_INTR; - } pin_controls_set(vmx, exec_control); /*