From: David Woodhouse <dwmw2@infradead.org>
To: Jim Mattson <jmattson@google.com>, KarimAllah Ahmed <karahmed@amazon.de>
Cc: kvm list <kvm@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
the arch/x86 maintainers <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 v5 2/5] KVM: x86: Add IBPB support
Date: Wed, 31 Jan 2018 19:53:18 +0000 [thread overview]
Message-ID: <1517428398.18619.197.camel@infradead.org> (raw)
In-Reply-To: <CALMp9eTNyjrQLViYkopsHp57saQwjNRnMTJt_pZVsaFvaUS9tQ@mail.gmail.com>
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On Wed, 2018-01-31 at 11:45 -0800, Jim Mattson wrote:
> On Wed, Jan 31, 2018 at 11:37 AM, KarimAllah Ahmed wrote:
>
> > + nested_vmx_disable_intercept_for_msr(msr_bitmap_l1, msr_bitmap_l0,
> > + MSR_IA32_PRED_CMD,
> > + MSR_TYPE_W);
> > +
>
> I still think this should be predicated on L1 having
> guest_cpuid_has(vcpu, X86_FEATURE_IBPB) or guest_cpuid_has(vcpu,
> X86_FEATURE_SPEC_CTRL), because of the potential impact to the
> hypertwin. If L0 denies the feature to L1 by clearing those CPUID
> bits, L1 shouldn't be able to bypass that restriction by launching L2.
Rather than doing the expensive guest_cpu_has() every time (which is
worse now as we realised we need two of them) perhaps we should
introduce a local flag for that too?
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next prev parent reply other threads:[~2018-01-31 19:53 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-31 19:37 [PATCH v5 0/5] KVM: Expose speculation control feature to guests KarimAllah Ahmed
2018-01-31 19:37 ` [PATCH v5 1/5] KVM: x86: Update the reverse_cpuid list to include CPUID_7_EDX KarimAllah Ahmed
2018-01-31 20:22 ` Konrad Rzeszutek Wilk
2018-01-31 19:37 ` [PATCH v5 2/5] KVM: x86: Add IBPB support KarimAllah Ahmed
2018-01-31 19:45 ` Jim Mattson
2018-01-31 19:53 ` David Woodhouse [this message]
2018-01-31 19:55 ` Jim Mattson
2018-02-01 0:27 ` KarimAllah Ahmed
2018-01-31 20:28 ` Konrad Rzeszutek Wilk
2018-01-31 20:36 ` KarimAllah Ahmed
2018-02-01 4:54 ` Tom Lendacky
2018-02-01 17:00 ` Raj, Ashok
2018-01-31 19:37 ` [PATCH v5 3/5] KVM: VMX: Emulate MSR_IA32_ARCH_CAPABILITIES KarimAllah Ahmed
2018-01-31 19:37 ` [PATCH v5 4/5] KVM: VMX: Allow direct access to MSR_IA32_SPEC_CTRL KarimAllah Ahmed
2018-01-31 19:53 ` Jim Mattson
2018-01-31 20:00 ` David Woodhouse
2018-01-31 20:01 ` KarimAllah Ahmed
2018-01-31 20:18 ` Jim Mattson
2018-01-31 20:21 ` David Woodhouse
2018-01-31 21:18 ` Jim Mattson
2018-01-31 22:05 ` David Woodhouse
2018-01-31 20:34 ` Paolo Bonzini
2018-01-31 20:54 ` Jim Mattson
2018-01-31 21:00 ` Paolo Bonzini
2018-01-31 21:05 ` Jim Mattson
2018-01-31 21:17 ` Woodhouse, David
2018-01-31 21:42 ` Paolo Bonzini
2018-01-31 21:53 ` Jim Mattson
2018-01-31 21:59 ` Paolo Bonzini
2018-01-31 21:59 ` David Woodhouse
2018-01-31 22:06 ` Jim Mattson
2018-01-31 22:10 ` David Woodhouse
2018-01-31 22:21 ` Linus Torvalds
2018-01-31 22:53 ` Andy Lutomirski
2018-02-01 14:09 ` Paolo Bonzini
2018-01-31 22:52 ` KarimAllah Ahmed
2018-02-01 0:24 ` KarimAllah Ahmed
2018-02-01 4:26 ` Konrad Rzeszutek Wilk
2018-02-01 13:25 ` David Woodhouse
2018-02-01 17:37 ` KarimAllah Ahmed
2018-02-01 17:46 ` KarimAllah Ahmed
2018-02-01 14:19 ` Konrad Rzeszutek Wilk
2018-02-01 14:28 ` KarimAllah Ahmed
2018-01-31 22:56 ` Raj, Ashok
2018-01-31 19:37 ` [PATCH v5 5/5] KVM: SVM: " KarimAllah Ahmed
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