linux-kernel - Re: [PATCH] KVM: x86: dump_vmcs should not assume GUEST_IA32

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Message-ID: <13461f99-09a3-6e9a-d015-2658a46b628a@redhat.com>
Date:   Thu, 18 Feb 2021 19:04:03 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Jim Mattson <jmattson@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     David Edmondson <dme@....org>, LKML <linux-kernel@...r.kernel.org>,
        Borislav Petkov <bp@...en8.de>,
        Wanpeng Li <wanpengli@...cent.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, kvm list <kvm@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH] KVM: x86: dump_vmcs should not assume GUEST_IA32_EFER is
 valid

On 18/02/21 18:55, Jim Mattson wrote:
>>> Got it now.  It would sort of help, because while dumping the MSR load/store
>>> area you could get hold of the real EFER, and use it to decide whether to
>>> dump the PDPTRs.
>> EFER isn't guaranteed to be in the load list, either, e.g. if guest and host
>> have the same desired value.
>>
>> The proper way to retrieve the effective EFER is to reuse the logic in
>> nested_vmx_calc_efer(), i.e. look at VM_ENTRY_IA32E_MODE if EFER isn't being
>> loaded via VMCS.
>
> Shouldn't dump_vmcs() simply dump the contents of the VMCS, in its
> entirety? What does it matter what the value of EFER is?

Currently it has some conditionals, but it wouldn't be a problem indeed 
to remove them.

The MSR load list is missing state that dump_vmcs should print though.

Paolo