This series removes X86_FEATURE_USE_IBPB, and fixes a KVM nVMX bug in the process. The motivation is mostly the confusing name of X86_FEATURE_USE_IBPB, which sounds like it controls IBPBs in general, but it only controls IBPBs for spectre_v2_mitigation. A side effect of this confusion is the nVMX bug, where virtualizing IBRS correctly depends on the spectre_v2_user mitigation. The feature bit is mostly redundant, except in controlling the IBPB in the vCPU load path. For that, a separate static branch is introduced, similar to switch_mm_*_ibpb. We should also unify indirect_branch_prediction_barrier() with entry_ibpb() to have a single IBPB primitive that always stuffs the RSB if needed. Josh will be sending follow up changes for that. v1 -> v2: - Collected Ack/Review tags (thanks everyone!). - Combined the if statements in vmx_vcpu_load_vmcs() and moved the static branch check ahead (Sean Christopherson). - Renamed the static branch to switch_vcpu_ibpb (Sean Christopherson). - Fixed a typo in the commit message (Jim Mattson). Yosry Ahmed (6): x86/bugs: Move the X86_FEATURE_USE_IBPB check into callers x86/mm: Remove X86_FEATURE_USE_IBPB checks in cond_mitigation() x86/bugs: Remove the X86_FEATURE_USE_IBPB check in ib_prctl_set() x86/bugs: Use a static branch to guard IBPB on vCPU switch KVM: nVMX: Always use IBPB to properly virtualize IBRS x86/bugs: Remove X86_FEATURE_USE_IBPB arch/x86/include/asm/cpufeatures.h | 1 - arch/x86/include/asm/nospec-branch.h | 4 +++- arch/x86/kernel/cpu/bugs.c | 6 +++++- arch/x86/kvm/svm/svm.c | 3 ++- arch/x86/kvm/vmx/vmx.c | 3 ++- arch/x86/mm/tlb.c | 3 +-- tools/arch/x86/include/asm/cpufeatures.h | 1 - 7 files changed, 13 insertions(+), 8 deletions(-) -- 2.48.1.658.g4767266eb4-goog
