Re: [PATCH RFC] KVM: async_pf: fix async_pf exception injection

From	Paolo Bonzini <pbonzini@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH RFC] KVM: async_pf: fix async_pf exception injection
Date	2017-06-08 14:50 +0200
Message-ID	<tQ52X-4l3-31@gated-at.bofh.it> (permalink)
References	<tQ255-2wu-33@gated-at.bofh.it> <tQ4gy-3MZ-15@gated-at.bofh.it> <tQ4Tg-4hK-21@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 08/06/2017 14:32, Wanpeng Li wrote:
>>> I change the
>>> condition to "nr == PF_VECTOR && error_code == 0" to intercept async_pf, however,
>>> the below bug will be splatted:
>> Right, because error_code == 0 is a valid error code.
>>
>> For stable releases, this should be enough:
> 
> We should also take care PAGE_READY async_pfs injection. I will send a
> patch to avoid async pf injection stuff in guest mode for stable
> release.

Right, the simplest thing to do here is another is_guest_mode check in
kvm_arch_can_inject_async_page_present.  That would delay the signaling
of ready pages while L2 runs, but hopefully we're under memory pressure
so L2 will get a page fault too.		

In fact, kvm_arch_can_inject_async_page_present should just be

        if (!(vcpu->arch.apf.msr_val & KVM_ASYNC_PF_ENABLED))
                return true;
        else
                return can_do_async_pf(vcpu);

where can_do_async_pf becomes nonstatic.
Paolo

Thread

[PATCH RFC] KVM: async_pf: fix async_pf exception injection Wanpeng Li <kernellwp@gmail.com> - 2017-06-08 11:40 +0200
  Re: [PATCH RFC] KVM: async_pf: fix async_pf exception injection Paolo Bonzini <pbonzini@redhat.com> - 2017-06-08 14:00 +0200
    Re: [PATCH RFC] KVM: async_pf: fix async_pf exception injection Wanpeng Li <kernellwp@gmail.com> - 2017-06-08 14:40 +0200
      Re: [PATCH RFC] KVM: async_pf: fix async_pf exception injection Paolo Bonzini <pbonzini@redhat.com> - 2017-06-08 14:50 +0200
    Re: [PATCH RFC] KVM: async_pf: fix async_pf exception injection Wanpeng Li <kernellwp@gmail.com> - 2017-06-09 07:40 +0200
      Re: [PATCH RFC] KVM: async_pf: fix async_pf exception injection Paolo Bonzini <pbonzini@redhat.com> - 2017-06-09 13:40 +0200

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