Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
To:     Jim Mattson <jmattson@google.com>,
        Sean Christopherson <seanjc@google.com>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>, Joerg Roedel <joro@8bytes.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        kvm list <kvm@vger.kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Vitaly Kuznetsov <vkuznets@redhat.com>
Subject: Re: [PATCH v2 1/3] KVM: x86: dump_vmcs should not assume
 GUEST_IA32_EFER is valid
In-Reply-To: <CALMp9eQ5HQqRRBu0HJbuTOJwKSUA950JWSHrLkXz7cHWKt+ymg@mail.gmail.com>
References: <20210219144632.2288189-1-david.edmondson@oracle.com>
 <20210219144632.2288189-2-david.edmondson@oracle.com>
 <YDWG51Io0VJEBHGg@google.com>
 <CALMp9eQ5HQqRRBu0HJbuTOJwKSUA950JWSHrLkXz7cHWKt+ymg@mail.gmail.com>
From:   David Edmondson <dme@dme.org>
Date:   Wed, 24 Feb 2021 13:30:23 +0000
Message-ID: <m235xlfv9s.fsf@dme.org>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On Tuesday, 2021-02-23 at 15:13:54 -08, Jim Mattson wrote:

> On Tue, Feb 23, 2021 at 2:51 PM Sean Christopherson <seanjc@google.com> wrote:
>>
>> On Fri, Feb 19, 2021, David Edmondson wrote:
>> > If the VM entry/exit controls for loading/saving MSR_EFER are either
>> > not available (an older processor or explicitly disabled) or not
>> > used (host and guest values are the same), reading GUEST_IA32_EFER
>> > from the VMCS returns an inaccurate value.
>> >
>> > Because of this, in dump_vmcs() don't use GUEST_IA32_EFER to decide
>> > whether to print the PDPTRs - do so if the EPT is in use and CR4.PAE
>> > is set.
>>
>> This isn't necessarily correct either.  In a way, it's less correct as PDPTRs
>> are more likely to be printed when they shouldn't, assuming most guests are
>> 64-bit guests.  It's annoying to calculate the effective guest EFER, but so
>> awful that it's worth risking confusion over PDTPRs.
>
> I still prefer a dump_vmcs that always dumps every VMCS field.

v3 now always shows the PDPTRs if they exist.

dme.
-- 
I've got a little black book with my poems in.