From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: David Woodhouse <dwmw2@infradead.org>
Cc: KarimAllah Ahmed <karahmed@amazon.de>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
x86@kernel.org, Ashok Raj <ashok.raj@intel.com>,
Asit Mallick <asit.k.mallick@intel.com>,
Dave Hansen <dave.hansen@intel.com>,
Arjan Van De Ven <arjan.van.de.ven@intel.com>,
Tim Chen <tim.c.chen@linux.intel.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Andi Kleen <ak@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Dan Williams <dan.j.williams@intel.com>,
Jun Nakajima <jun.nakajima@intel.com>,
Andy Lutomirski <luto@kernel.org>,
Greg KH <gregkh@linuxfoundation.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v6 2/5] KVM: x86: Add IBPB support
Date: Fri, 2 Feb 2018 15:52:20 -0500 [thread overview]
Message-ID: <20180202205220.GA2516@char.us.oracle.com> (raw)
In-Reply-To: <1517603487.31953.76.camel@infradead.org>
On Fri, Feb 02, 2018 at 08:31:27PM +0000, David Woodhouse wrote:
> On Fri, 2018-02-02 at 15:28 -0500, Konrad Rzeszutek Wilk wrote:
> >
> > >
> > > No. The AMD feature bits give us more fine-grained support for exposing
> > > IBPB or IBRS alone, so we expose those bits on Intel too.
> >
> > But but.. that runs smack against the idea of exposing a platform that
> > is as close to emulating the real hardware as possible.
> >
> > As in I would never expect an Intel CPU to expose the IBPB on the 0x8000_0008
> > leaf. Hence KVM (nor any hypervisor) should not do it either.
> >
> > Unless Intel is doing it? Did I miss a new spec update?
>
> Are you telling me there's no way you can infer from CPUID that you're
> running in a hypervisor?
That is not what I am saying. The CPUIDs 0x40000000 ... 0x400000ff
are reserved for hypervisor usage. The SDM is pretty clear about it.
The Intel SDM and the AMD equivalant are pretty clear about what the
other leafs should have on its platform.
[5 minutes later]
And I am eating my words here.
CPUID.80000008 shows how MAXPHYSADDR is used (on the Intel SDM).
Never mind the noise.
next prev parent reply other threads:[~2018-02-02 20:53 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-01 21:59 [PATCH v6 0/5] KVM: Expose speculation control feature to guests KarimAllah Ahmed
2018-02-01 21:59 ` [PATCH v6 1/5] KVM: x86: Update the reverse_cpuid list to include CPUID_7_EDX KarimAllah Ahmed
2018-02-02 17:37 ` Jim Mattson
2018-02-01 21:59 ` [PATCH v6 2/5] KVM: x86: Add IBPB support KarimAllah Ahmed
2018-02-02 17:49 ` Konrad Rzeszutek Wilk
2018-02-02 18:02 ` David Woodhouse
2018-02-02 19:56 ` Konrad Rzeszutek Wilk
2018-02-02 20:16 ` David Woodhouse
2018-02-02 20:28 ` Konrad Rzeszutek Wilk
2018-02-02 20:31 ` David Woodhouse
2018-02-02 20:52 ` Konrad Rzeszutek Wilk [this message]
2018-02-02 20:52 ` Alan Cox
2018-02-05 19:22 ` Paolo Bonzini
2018-02-05 19:24 ` Paolo Bonzini
2018-02-16 3:44 ` Jim Mattson
2018-02-16 4:22 ` Andi Kleen
2018-05-03 1:27 ` Wanpeng Li
2018-05-03 9:19 ` Paolo Bonzini
2018-05-03 12:01 ` Wanpeng Li
2018-05-03 12:46 ` Tian, Kevin
2018-02-01 21:59 ` [PATCH v6 3/5] KVM: VMX: Emulate MSR_IA32_ARCH_CAPABILITIES KarimAllah Ahmed
2018-02-02 10:53 ` Darren Kenny
2018-02-02 17:35 ` Jim Mattson
2018-02-02 17:51 ` Konrad Rzeszutek Wilk
2018-02-01 21:59 ` [PATCH v6 4/5] KVM: VMX: Allow direct access to MSR_IA32_SPEC_CTRL KarimAllah Ahmed
2018-02-02 11:03 ` Darren Kenny
2018-02-02 11:27 ` David Woodhouse
2018-02-02 17:53 ` Konrad Rzeszutek Wilk
2018-02-02 18:05 ` David Woodhouse
2018-02-02 18:19 ` Konrad Rzeszutek Wilk
2018-02-02 17:57 ` Jim Mattson
2018-02-01 21:59 ` [PATCH v6 5/5] KVM: SVM: " KarimAllah Ahmed
2018-02-02 11:06 ` Darren Kenny
2018-02-02 18:02 ` Konrad Rzeszutek Wilk
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