On 05/03/17 13:01, Jan Beulich wrote: >>>> On 03.05.17 at 11:10, <rcojoc...@bitdefender.com> wrote: >> The introspection agent can reply to a vm_event faster than >> vmx_vmexit_handler() can complete in some cases, where it is then >> not safe for vm_event_set_registers() to modify v->arch.user_regs. >> In the test scenario, we were stepping over an INT3 breakpoint by >> setting RIP += 1. The quick reply tended to complete before the VCPU >> triggering the introspection event had properly paused and been >> descheduled. If the reply occurs before __context_switch() happens, >> __context_switch() clobbers the reply by overwriting >> v->arch.user_regs from the stack. If the reply occurs after >> __context_switch(), we don't pass through __context_switch() when >> transitioning to idle. > > This last sentence still looks to be wrong (and even self-contradictory). > The reply can't occur after __context_switch() if we don't make it there > in the first place. How about "If we don't pass through > __context_switch() (due to switching to the idle vCPU), reply data > wouldn't be picked up when switching back straight to the original > vCPU"?
Quite right, it's very convoluted. I'll update the comment. Thanks, Razvan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
