[Xen-devel] SVM Trap Flag exiting?

[Cutter 409 <cutter409@xxxxxxxxx>]

I'm having a really hard time trying to accomplish something that seems generally simple. I want to single step some code in an SVM guest.

My current method essentially does the following:

From a domctl:

   * Pause the target VCPU
   * vmcb_set_exception_intercepts(vmcb, vmcb_get_exception_intercepts(vmcb) | (1U << TRAP_debug) );
   * v->arch.guest_context.user_regs.rflags |= X86_EFLAGS_TF;
   * I've also tried vmcb->rflags |= X86_EFLAGS_TF;
   * Unpause the VCPU

But the VMEXIT_EXCEPTION_DB case doesn't ever seem to get called. Is there something I'm missing here?
I've also tried setting both versions of rflags in svm_do_resume() but it doesn't make a difference.The guest doesn't crash either, so I'm assuming TF is just not getting set.

Any thoughts would be greatly appreciated.

Thanks!


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