2018-03-23 09:34-0700, Sean Christopherson: > Exit to userspace with KVM_INTERNAL_ERROR_EMULATION if we encounter > an exception in Protected Mode while emulating guest due to invalid > guest state. Unlike Big RM, KVM doesn't support emulating exceptions > in PM, i.e. PM exceptions are always injected via the VMCS. Because > we will never do VMRESUME due to emulation_required, the exception is > never realized and we'll keep emulating the faulting instruction over > and over until we receive a signal. > > Exit to userspace iff there is a pending exception, i.e. don't exit > simply on a requested event. The purpose of this check and exit is to > aid in debugging a guest that is in all likelihood already doomed. > Invalid guest state in PM is extremely limited in normal operation, > e.g. it generally only occurs for a few instructions early in BIOS, > and any exception at this time is all but guaranteed to be fatal. > Non-vectored interrupts, e.g. INIT, SIPI and SMI, can be cleanly > handled/emulated, while checking for vectored interrupts, e.g. INTR > and NMI, without hitting false positives would add a fair amount of > complexity for almost no benefit (getting hit by lightning seems > more likely than encountering this specific scenario). > > Add a WARN_ON_ONCE to vmx_queue_exception() if we try to inject an > exception via the VMCS and emulation_required is true. > > Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> > --- Queued, thanks.
