linux-kernel - Re: [PATCH 4.19 067/306] KVM: nVMX: move check_vmentry_postreqs() call to nested_vmx_enter_non_root

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Message-ID: <bccbfccd-0e96-29c3-b2ba-2b1800364b08@redhat.com>
Date:   Mon, 2 Dec 2019 16:09:33 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jack Wang <jack.wang.usish@...il.com>
Cc:     linux-kernel@...r.kernel.org, stable <stable@...r.kernel.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Jim Mattson <jmattson@...gle.com>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 067/306] KVM: nVMX: move check_vmentry_postreqs()
 call to nested_vmx_enter_non_root_mode()

On 02/12/19 15:51, Greg Kroah-Hartman wrote:
> On Mon, Dec 02, 2019 at 03:40:04PM +0100, Jack Wang wrote:
>> Greg Kroah-Hartman <gregkh@...uxfoundation.org> 于2019年11月27日周三 下午10:30写道：
>>>
>>> From: Sean Christopherson <sean.j.christopherson@...el.com>
>>>
>>> [ Upstream commit 7671ce21b13b9596163a29f4712cb2451a9b97dc ]
>>>
>>> In preparation of supporting checkpoint/restore for nested state,
>>> commit ca0bde28f2ed ("kvm: nVMX: Split VMCS checks from nested_vmx_run()")
>>> modified check_vmentry_postreqs() to only perform the guest EFER
>>> consistency checks when nested_run_pending is true.  But, in the
>>> normal nested VMEntry flow, nested_run_pending is only set after
>>> check_vmentry_postreqs(), i.e. the consistency check is being skipped.
>>>
>>> Alternatively, nested_run_pending could be set prior to calling
>>> check_vmentry_postreqs() in nested_vmx_run(), but placing the
>>> consistency checks in nested_vmx_enter_non_root_mode() allows us
>>> to split prepare_vmcs02() and interleave the preparation with
>>> the consistency checks without having to change the call sites
>>> of nested_vmx_enter_non_root_mode().  In other words, the rest
>>> of the consistency check code in nested_vmx_run() will be joining
>>> the postreqs checks in future patches.
>>>
>>> Fixes: ca0bde28f2ed ("kvm: nVMX: Split VMCS checks from nested_vmx_run()")
>>> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
>>> Cc: Jim Mattson <jmattson@...gle.com>
>>> Reviewed-by: Jim Mattson <jmattson@...gle.com>
>>> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
>>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>>> ---
>>>  arch/x86/kvm/vmx.c | 10 +++-------
>>>  1 file changed, 3 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>>> index fe7fdd666f091..bdf019f322117 100644
>>> --- a/arch/x86/kvm/vmx.c
>>> +++ b/arch/x86/kvm/vmx.c
>>> @@ -12694,6 +12694,9 @@ static int enter_vmx_non_root_mode(struct kvm_vcpu *vcpu, u32 *exit_qual)
>>>         if (likely(!evaluate_pending_interrupts) && kvm_vcpu_apicv_active(vcpu))
>>>                 evaluate_pending_interrupts |= vmx_has_apicv_interrupt(vcpu);
>>>
>>> +       if (from_vmentry && check_vmentry_postreqs(vcpu, vmcs12, exit_qual))
>>> +               return EXIT_REASON_INVALID_STATE;
>>> +
>>>         enter_guest_mode(vcpu);
>>>
>>>         if (!(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_DEBUG_CONTROLS))
>>> @@ -12836,13 +12839,6 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
>>>          */
>>>         skip_emulated_instruction(vcpu);
>>>
>>> -       ret = check_vmentry_postreqs(vcpu, vmcs12, &exit_qual);
>>> -       if (ret) {
>>> -               nested_vmx_entry_failure(vcpu, vmcs12,
>>> -                                        EXIT_REASON_INVALID_STATE, exit_qual);
>>> -               return 1;
>>> -       }
>>> -
>>>         /*
>>>          * We're finally done with prerequisite checking, and can start with
>>>          * the nested entry.
>>> --
>>> 2.20.1
>>>
>>>
>>>
>> Hi all,
>>
>> This commit caused many kvm-unit-tests regression, cherry-pick
>> following commits from 4.20 fix the regression:
>> d63907dc7dd1 ("KVM: nVMX: rename enter_vmx_non_root_mode to
>> nested_vmx_enter_non_root_mode")
>> a633e41e7362 ("KVM: nVMX: assimilate nested_vmx_entry_failure() into
>> nested_vmx_enter_non_root_mode()")
> 
> Now queued up, thanks!
> 
> greg k-h
> 

Why was it backported anyway?  Can everybody please just stop applying
KVM patches to stable kernels unless CCed to stable@...r.kernel.org?

I thought I had already asked Sasha to opt out of the autoselect
nonsense after catching another bug that would have been introduced.

Paolo