From: Jim Mattson <jmattson@google.com>
To: Sean Christopherson <seanjc@google.com>
Cc: David Edmondson <david.edmondson@oracle.com>,
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
Date: Tue, 23 Feb 2021 15:13:54 -0800 [thread overview]
Message-ID: <CALMp9eQ5HQqRRBu0HJbuTOJwKSUA950JWSHrLkXz7cHWKt+ymg@mail.gmail.com> (raw)
In-Reply-To: <YDWG51Io0VJEBHGg@google.com>
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. But if
you really want to skip printing the PDPTEs when they're irrelevant,
can't you just use the "IA-32e mode guest" VM-entry control as a proxy
for EFER.LMA?
next prev parent reply other threads:[~2021-02-23 23:19 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-19 14:46 [PATCH v2 0/3] KVM: x86: dump_vmcs: don't assume GUEST_IA32_EFER, show MSR autoloads/autosaves David Edmondson
2021-02-19 14:46 ` [PATCH v2 1/3] KVM: x86: dump_vmcs should not assume GUEST_IA32_EFER is valid David Edmondson
2021-02-23 22:51 ` Sean Christopherson
2021-02-23 23:13 ` Jim Mattson [this message]
2021-02-23 23:41 ` Sean Christopherson
2021-02-24 13:30 ` David Edmondson
2021-02-23 23:18 ` Jim Mattson
2021-02-19 14:46 ` [PATCH v2 2/3] KVM: x86: dump_vmcs should not conflate EFER and PAT presence in VMCS David Edmondson
2021-02-23 22:58 ` Sean Christopherson
2021-02-24 13:31 ` David Edmondson
2021-02-19 14:46 ` [PATCH v2 3/3] KVM: x86: dump_vmcs should include the autoload/autostore MSR lists David Edmondson
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