From: "Raj, Ashok" <ashok.raj@intel.com>
To: KarimAllah Ahmed <karahmed@amazon.de>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
x86@kernel.org, Asit Mallick <asit.k.mallick@intel.com>,
Arjan Van De Ven <arjan.van.de.ven@intel.com>,
Dave Hansen <dave.hansen@intel.com>,
Andi Kleen <ak@linux.intel.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Tim Chen <tim.c.chen@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Dan Williams <dan.j.williams@intel.com>,
Jun Nakajima <jun.nakajima@intel.com>,
Paolo Bonzini <pbonzini@redhat.com>,
David Woodhouse <dwmw@amazon.co.uk>,
Greg KH <gregkh@linuxfoundation.org>,
Andy Lutomirski <luto@kernel.org>,
Ashok Raj <ashok.raj@intel.com>
Subject: Re: [PATCH v5 4/5] KVM: VMX: Allow direct access to MSR_IA32_SPEC_CTRL
Date: Wed, 31 Jan 2018 14:56:42 -0800 [thread overview]
Message-ID: <20180131225642.GA39829@otc-nc-03> (raw)
In-Reply-To: <1517427467-28567-5-git-send-email-karahmed@amazon.de>
Hi Karim
On Wed, Jan 31, 2018 at 08:37:46PM +0100, KarimAllah Ahmed wrote:
> [ Based on a patch from Ashok Raj <ashok.raj@intel.com> ]
>
> Add direct access to MSR_IA32_SPEC_CTRL for guests. This is needed for
> guests that will only mitigate Spectre V2 through IBRS+IBPB and will not
> be using a retpoline+IBPB based approach.
With these changes SPEC_CTRL is properly exposed to the guest when using
latest Qemu.
>
> To avoid the overhead of atomically saving and restoring the
> MSR_IA32_SPEC_CTRL for guests that do not actually use the MSR, only
> add_atomic_switch_msr when a non-zero is written to it.
>
> No attempt is made to handle STIBP here, intentionally. Filtering STIBP
> may be added in a future patch, which may require trapping all writes
> if we don't want to pass it through directly to the guest.
>
> [dwmw2: Clean up CPUID bits, save/restore manually, handle reset]
>
next prev parent reply other threads:[~2018-01-31 22:56 UTC|newest]
Thread overview: 51+ 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 ` 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
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 21:17 ` 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
2018-01-31 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 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 14:19 ` Konrad Rzeszutek Wilk
2018-02-01 14:28 ` KarimAllah Ahmed
2018-02-01 14:28 ` KarimAllah Ahmed
2018-01-31 22:56 ` Raj, Ashok [this message]
2018-01-31 19:37 ` [PATCH v5 5/5] KVM: SVM: " KarimAllah Ahmed
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