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3a7c8fafd1
The async page fault injection into kernel space creates more problems than it solves. The host has absolutely no knowledge about the state of the guest if the fault happens in CPL0. The only restriction for the host is interrupt disabled state. If interrupts are enabled in the guest then the exception can hit arbitrary code. The HALT based wait in non-preemotible code is a hacky replacement for a proper hypercall. For the ongoing work to restrict instrumentation and make the RCU idle interaction well defined the required extra work for supporting async pagefault in CPL0 is just not justified and creates complexity for a dubious benefit. The CPL3 injection is well defined and does not cause any issues as it is more or less the same as a regular page fault from CPL3. Suggested-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com> Acked-by: Paolo Bonzini <pbonzini@redhat.com> Acked-by: Peter Zijlstra <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200505134059.369802541@linutronix.de |
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