KVM: x86: fix failure of injecting exceptions inx86_emulate_instruction
A message that is not in the archive (sent off-list or not yet received): [email protected]
Paolo Bonzini
maintainerQuoted 4 lines · On 21/09/2018 04:08, [email protected] wrote:
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Quoted 4 lines
Unqueued, sorry. The hypercall test from kvm-unit-tests fails. A VMCALL on the "edge" of canonical address space, i.e. at
0x7ffffffffffd, raises a general protection fault before this patch and a double fault afterwards.
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Peng Hao submitted a very similar patch[1], the difference being that it also modified
x86_emulate_instruction()to ignore the result ofinject_emulated_exception(). I have no idea if that change is correct but it may be related to the aforementioned unit test failing.The return value of
inject_emulated_exceptionfor #PF represents whether in nested vcpu, not about the success or failure. Because we are not in nested vcpu,inject_emulated_exceptionmust return false. And for other exceptions,inject_emulated_exceptionjust return false. After propagating exceptions to guest, we just should return to guest mode and let guest handle.
Yes, your patch should work, and the x86_emulate_instruction code that is there now is clearly wrong (though I'm not sure how the double-fault comes up, #GP + #UD shouldn't generate one because #UD is a benign exception).
Peng Hao, do you have a testcase? Eduardo's kvm-unit-tests patch from Nov 2017 doesn't reproduce the bug anymore for me.
Thanks,
Paolo