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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Date:   Wed, 4 Dec 2019 11:50:33 -0600
From:   Dan Rue <dan.rue@...aro.org>
To:     Jack Wang <jack.wang.usish@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable <stable@...r.kernel.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Jim Mattson <jmattson@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.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 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:

Hi Jack - can you be more specific about the failing tests? What type of
environment and which tests failed, which version of kvm-unit-tests? Do
you have any logs available? I ask because we do run kvm-unit-tests on
x86 and arm64 but we did not see these regressions.

Thanks,
Dan

> 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()")
> 
> Regards,
> Jack Wang
> 1 & 1 IONOS SE

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