linux-kernel - Re: [BISECTED] KVM error with 5.0-rc

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Date:   Mon, 14 Jan 2019 10:33:19 -0800
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Harald Arnesen <harald@...gtun.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [BISECTED] KVM error with 5.0-rc

On Mon, Jan 14, 2019 at 06:04:27PM +0100, Harald Arnesen wrote:
> Qemu with KVM acceleration fails with kernel 5.0-rc1 and 5.0-rc2.
> It works fine with 4.20.

...

> Bisecting gives:
> 
> c73da3fcab43357feb68cac227194b13e998a8db is the first bad commit
> commit c73da3fcab43357feb68cac227194b13e998a8db
> Author: Sean Christopherson <sean.j.christopherson@...el.com>
> Date:   Mon Dec 3 13:53:00 2018 -0800
> 
>     KVM: VMX: Properly handle dynamic VM Entry/Exit controls
> 
>     EFER and PERF_GLOBAL_CTRL MSRs have dedicated VM Entry/Exit controls
>     that KVM dynamically toggles based on whether or not the guest's value
>     for each MSRs differs from the host.  Handle the dynamic behavior by
>     adding a helper that clears the dynamic bits so the bits aren't set
>     when initializing the VMCS field outside of the dynamic toggling flow.
>     This makes the handling consistent with similar behavior for other
>     controls, e.g. pin, exec and sec_exec.  More importantly, it eliminates
>     two global bools that are stealthily modified by setup_vmcs_config.
> 
>     Opportunistically clean up a comment and print related to errata for
>     IA32_PERF_GLOBAL_CTRL.
> 
>     Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
>     Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>

Can you test the attached patch?  Found a bug when re-inspecting the
guilty commit, the wrong VMCS field is being modifying when applying an
errata to disable VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL.  Your CPU is
listed as one of the models affected by the errata.  Compile tested only.

View attachment "0001-KVM-VMX-Use-the-correct-var-field-when-clearing-VM_E.patch" of type "text/x-diff" (1333 bytes)