linux-kernel - Re: [PATCH 0/2] RFC: VMX: fix for disappearing L1->L2 event injection on L1 migration

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Date:   Wed, 6 Jan 2021 10:07:51 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>
Cc:     kvm@...r.kernel.org, Joerg Roedel <joro@...tes.org>,
        Wanpeng Li <wanpengli@...cent.com>,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@...r.kernel.org>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Jim Mattson <jmattson@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 0/2] RFC: VMX: fix for disappearing L1->L2 event
 injection on L1 migration

On Wed, Jan 06, 2021, Maxim Levitsky wrote:
> This is VMX version of the same issue as I reproduced on SVM.
> 
> Unlike SVM, this version has 2 pending issues to resolve.
> 
> 1. This seems to break 'vmx' kvm-unit-test in
> 'error code <-> (!URG || prot_mode) [+]' case.
> 
> The test basically tries to do nested vm entry with unrestricted guest disabled,
> real mode, and for some reason that works without patch 2 of this series and it
> doesn't cause the #GP to be injected, but with this patch the test complains
> about unexpected #GP.

An unexpected #GP for that test is very unlikely.  The various sub-tests under
vmx_controls_test() should never fully enter the guest as GUEST.RFLAGS is set to
an invalid value.  And, that specific test does VM-Enter with URG=0 and
CR0.PG/PE=0, which is also invalid.  The unit test uses test_vmx_valid_controls(),
which is a wee bit misleading, as the "early" consistency checks that cause
VM-Fail are expected to succeed, while the VM-Enter is still expected to "fail"
due to a consistency check VM-Exit.

> I suspect that this test case is broken, but this has to be investigated.
> 
> 2. L1 MTF injections are lost since kvm has no notion of them, this is TBD to
> be fixed.
> 
> This was lightly tested on my nested migration test which no VMX sadly still
> crashes and burns on an (likely) unrelated issue.
> 
> Best regards,
> 	Maxim Levitsky
> 
> Maxim Levitsky (2):
>   KVM: VMX: create vmx_process_injected_event
>   KVM: nVMX: fix for disappearing L1->L2 event injection on L1 migration
> 
>  arch/x86/kvm/vmx/nested.c | 12 ++++----
>  arch/x86/kvm/vmx/vmx.c    | 60 ++++++++++++++++++++++++---------------
>  arch/x86/kvm/vmx/vmx.h    |  4 +++
>  3 files changed, 47 insertions(+), 29 deletions(-)
> 
> -- 
> 2.26.2
> 
>