On 3/21/23 19:22, Li, Xin3 wrote: >> If there is no other concrete reason other than overflowing for assigning NMI and >> #DB with a stack level > 0, #VE should also be assigned with a stack level > 0, and >> #BP too. #VE can happen anytime and anywhere, so it is subject to overflowing too. > With IDT, both #VE and #BP do not use IST, but NMI, #DB, #MC and #DF do. > > Let's keep this "secret" logic for now, i.e., not change the stack levels > for #VE and #BP at this point. We can do "optimization", i.e., change them > later 😄. #VE also can't happen anywhere. There is some documentation about it in here: https://docs.kernel.org/x86/tdx.html#linux-ve-handler But, basically, the only halfway sane thing a guest might do to hit a #VE is touch some "MMIO". The host can *not* cause them in arbitrary places because of the SEPT_VE_DISABLE attribute. #VE's also can't nest until after the guest retrieves the "VE info". That means that the #VE handler at _least_ reaches C code before it's subject to another #VE and that second one would still need to be induced by something the guest does explicitly.
