* Re: [PATCH] KVM: x86: fix failure of injecting exceptions inx86_emulate_instruction
[not found] <201809211008185136372@zte.com.cn>
@ 2018-09-21 5:13 ` Paolo Bonzini
0 siblings, 0 replies; only message in thread
From: Paolo Bonzini @ 2018-09-21 5:13 UTC (permalink / raw)
To: peng.hao2, sean.j.christopherson
Cc: wang.yi59, rkrcmar, tglx, mingo, hpa, x86, kvm, linux-kernel,
zhong.weidong, xu.xi8, jiang.biao2
On 21/09/2018 04:08, peng.hao2@zte.com.cn wrote:
>>> 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.
>> Peng Hao submitted a very similar patch[1], the difference being that
>> it also modified x86_emulate_instruction() to ignore the result of
>> inject_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_exception for #PF represents whether in nested vcpu,
> not about the success or failure. Because we are not in nested vcpu, inject_emulated_exception
> must return false. And for other exceptions, inject_emulated_exception just 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
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