linux-kernel - Re: [PATCH] KVM: nVMX: Fix exception injection

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Date:   Mon, 24 Jul 2017 15:02:31 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Jim Mattson <jmattson@...gle.com>, Wanpeng Li <kernellwp@...il.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        kvm <kvm@...r.kernel.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>
Subject: Re: [PATCH] KVM: nVMX: Fix exception injection

On 23/07/2017 03:11, Jim Mattson wrote:
>>> In the situation you describe, the #PF causes a synthesized VM-exit
>>> from L2 to L1 directly, not indirectly. From the SDM:
>>>
>>>    An exception causes a VM exit directly if the bit corresponding to
>>> that exception is set in the exception bitmap.
>>>
>>> Hence, CR2 should not be set yet.
>>
>> Any idea how to synthesize exit qualification for page fault and debug
>> exception?
>
> I think the ancillary data for #DB and #PF should be added to
> kvm_queued_exception and plumbed through to where it's needed. Vector
> number and error code are not sufficient to describe a #DB or #PF.

It's more complicated than that, because you'd have to copy it out to
userspace in KVM_GET_VCPU_EVENTS.  But I agree it's the way to go: CR2
and DR6 should be only by inject_pending_event.

Paolo