Messages in this thread Patch in this message | | | Date | Tue, 05 May 2020 15:41:25 +0200 | From | Thomas Gleixner <> | Subject | [patch V4 part 2 13/18] x86/kvm: Move context tracking where it belongs |
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Context tracking for KVM happens way too early in the vcpu_run() code. Anything after guest_enter_irqoff() and before guest_exit_irqoff() cannot use RCU and should also be not instrumented.
The current way of doing this covers way too much code. Move it closer to the actual vmenter/exit code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Sean Christopherson <sean.j.christopherson@intel.com> --- arch/x86/kvm/svm/svm.c | 16 ++++++++++++++++ arch/x86/kvm/vmx/vmx.c | 10 ++++++++++ arch/x86/kvm/x86.c | 2 -- 3 files changed, 26 insertions(+), 2 deletions(-)
--- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -3330,6 +3330,14 @@ static void svm_vcpu_run(struct kvm_vcpu */ x86_spec_ctrl_set_guest(svm->spec_ctrl, svm->virt_spec_ctrl); + /* + * Tell context tracking that this CPU is about to enter guest + * mode. This has to be after x86_spec_ctrl_set_guest() because + * that can take locks (lockdep needs RCU) and calls into world and + * some more. + */ + guest_enter_irqoff(); + __svm_vcpu_run(svm->vmcb_pa, (unsigned long *)&svm->vcpu.arch.regs); #ifdef CONFIG_X86_64 @@ -3340,6 +3348,14 @@ static void svm_vcpu_run(struct kvm_vcpu loadsegment(gs, svm->host.gs); #endif #endif + /* + * Tell context tracking that this CPU is back. + * + * This needs to be done before the below as native_read_msr() + * contains a tracepoint and x86_spec_ctrl_restore_host() calls + * into world and some more. + */ + guest_exit_irqoff(); /* * We do not use IBRS in the kernel. If this vCPU has used the --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6603,6 +6603,11 @@ static void vmx_vcpu_run(struct kvm_vcpu */ x86_spec_ctrl_set_guest(vmx->spec_ctrl, 0); + /* + * Tell context tracking that this CPU is about to enter guest mode. + */ + guest_enter_irqoff(); + /* L1D Flush includes CPU buffer clear to mitigate MDS */ if (static_branch_unlikely(&vmx_l1d_should_flush)) vmx_l1d_flush(vcpu); @@ -6618,6 +6623,11 @@ static void vmx_vcpu_run(struct kvm_vcpu vcpu->arch.cr2 = read_cr2(); /* + * Tell context tracking that this CPU is back. + */ + guest_exit_irqoff(); + + /* * We do not use IBRS in the kernel. If this vCPU has used the * SPEC_CTRL MSR it may have left it on; save the value and * turn it off. This is much more efficient than blindly adding --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8404,7 +8404,6 @@ static int vcpu_enter_guest(struct kvm_v } trace_kvm_entry(vcpu->vcpu_id); - guest_enter_irqoff(); fpregs_assert_state_consistent(); if (test_thread_flag(TIF_NEED_FPU_LOAD)) @@ -8467,7 +8466,6 @@ static int vcpu_enter_guest(struct kvm_v local_irq_disable(); kvm_after_interrupt(vcpu); - guest_exit_irqoff(); if (lapic_in_kernel(vcpu)) { s64 delta = vcpu->arch.apic->lapic_timer.advance_expire_delta; if (delta != S64_MIN) {
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