Messages in this thread | | | Date | Wed, 15 Jul 2020 11:13:37 +0200 | From | Joerg Roedel <> | Subject | Re: [PATCH v4 63/75] x86/sev-es: Handle #DB Events |
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On Wed, Jul 15, 2020 at 10:47:52AM +0200, Peter Zijlstra wrote: > On Tue, Jul 14, 2020 at 02:09:05PM +0200, Joerg Roedel wrote: > > > @@ -1028,6 +1036,16 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication) > > struct ghcb *ghcb; > > > > lockdep_assert_irqs_disabled(); > > + > > + /* > > + * #DB is special and needs to be handled outside of the intrumentation_begin()/end(). > > + * Otherwise the #VC handler could be raised recursivly. > > + */ > > + if (error_code == SVM_EXIT_EXCP_BASE + X86_TRAP_DB) { > > + vc_handle_trap_db(regs); > > + return; > > + } > > + > > instrumentation_begin(); > > Wait what?! That makes no sense what so ever.
Then my understanding of intrumentation_begin/end() is wrong, I thought that the kernel will forbid setting breakpoints before instrumentation_begin(), which is necessary here because a break-point in the #VC handler might cause recursive #VC-exceptions when #DB is intercepted. Maybe you can elaborate on why this makes no sense?
Regards,
Joerg
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