KVM: SVM: fix random segfaults with NPT enabled

(cherry picked from commit 44874f84918e37b64bec6df1587e5fe2fdf6ab62)

This patch introduces a guest TLB flush on every NPF exit in KVM. This fixes
random segfaults and #UD exceptions in the guest seen under some workloads
(e.g. long running compile workloads or tbench). A kernbench run with and
without that fix showed that it has a slowdown lower than 0.5%

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@qumranet.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 7d6071d11eb89c8ee310024d907711e4c2038a38..fe88513a329606749e1433d8abf749880c051e5b 100644 (file)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -60,6 +60,7 @@ static int npt = 1;
 module_param(npt, int, S_IRUGO);
 
 static void kvm_reput_irq(struct vcpu_svm *svm);
+static void svm_flush_tlb(struct kvm_vcpu *vcpu);
 
 static inline struct vcpu_svm *to_svm(struct kvm_vcpu *vcpu)
 {
@@ -1017,6 +1018,15 @@ static int pf_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run)
 
        fault_address  = svm->vmcb->control.exit_info_2;
        error_code = svm->vmcb->control.exit_info_1;
+
+       /*
+        * FIXME: Tis shouldn't be necessary here, but there is a flush
+        * missing in the MMU code. Until we find this bug, flush the
+        * complete TLB here on an NPF
+        */
+       if (npt_enabled)
+               svm_flush_tlb(&svm->vcpu);
+
        if (event_injection)
                kvm_mmu_unprotect_page_virt(&svm->vcpu, fault_address);
        return kvm_mmu_page_fault(&svm->vcpu, fault_address, error_code);