On Sat, 11 Aug 2018, Thomas Gleixner wrote: > On Sat, 11 Aug 2018, Matthew Wilcox wrote: > > > On Sat, Aug 11, 2018 at 12:28:24PM +0500, Mikhail Gavrilov wrote: > > > Hi guys. > > > I am catched new bug. It occured when I start virtual machine. > > > Can anyone look? > > > > I'd suggest that st->lock should be taken with irqsave. Like this; > > please test. > > That should fix it, but that's suboptimal because that's an extra > safe/restore in switch_to(). So we better disable interrupts at the other > call site. Patch below. Which is wrong as well. The placement of the speculation update call in the SVM code should be moved, so just SVM is affected by a slightly larger irq disabled region and no overhead at all for all others. Revised patch below. Thanks, tglx 8<------------------ diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index f059a73f0fd0..9c9b976d1afd 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -5580,8 +5580,6 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu) clgi(); - local_irq_enable(); - /* * If this vCPU has touched SPEC_CTRL, restore the guest's value if * it's non-zero. Since vmentry is serialising on affected CPUs, there @@ -5590,6 +5588,8 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu) */ x86_spec_ctrl_set_guest(svm->spec_ctrl, svm->virt_spec_ctrl); + local_irq_enable(); + asm volatile ( "push %%" _ASM_BP "; \n\t" "mov %c[rbx](%[svm]), %%" _ASM_BX " \n\t"
