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: <CA+res+SffBsmmeEBYfoDwyLHvL8nqW+O=ZKedWCxccmQ9X6itA@mail.gmail.com>
Date:   Tue, 3 Dec 2019 10:21:35 +0100
From:   Jack Wang <jack.wang.usish@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.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>,
        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()

Paolo Bonzini <pbonzini@...hat.com> 于2019年12月2日周一 下午4:09写道：
>
> 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
>
Hi Paolo,

Should we simply revert the patch, maybe also
9fe573d539a8 ("KVM: nVMX: reset cache/shadows when switching loaded VMCS")

Both of them are from one big patchset:
https://patchwork.kernel.org/cover/10616179/

Revert both patches recover the regression I see on kvm-unit-tests.

Thanks,
Jack Wang