Re: [PATCH] KVM: x86: dump_vmcs should not assume GUEST_IA32_EFER is valid

From: Paolo Bonzini <pbonzini@redhat.com>
To: Jim Mattson <jmattson@google.com>,
	Sean Christopherson <seanjc@google.com>
Cc: David Edmondson <dme@dme.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Borislav Petkov <bp@alien8.de>,
	Wanpeng Li <wanpengli@tencent.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	the arch/x86 maintainers <x86@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>, kvm list <kvm@vger.kernel.org>,
	Joerg Roedel <joro@8bytes.org>
Subject: Re: [PATCH] KVM: x86: dump_vmcs should not assume GUEST_IA32_EFER is valid
Date: Thu, 18 Feb 2021 19:04:03 +0100	[thread overview]
Message-ID: <13461f99-09a3-6e9a-d015-2658a46b628a@redhat.com> (raw)
In-Reply-To: <CALMp9eTX4Na2VTY2aU=-SUrGhst5aExdCB3f=4krKj1mFPgcqQ@mail.gmail.com>

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