linux-kernel - Re: [PATCH v3 00/18] arm64: Add SMCCC v1.1 support and CVE-2017-5715 (Spectre variant 2) mitigation

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Date:   Thu, 1 Feb 2018 13:59:45 +0000
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        kvmarm <kvmarm@...ts.cs.columbia.edu>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Peter Maydell <peter.maydell@...aro.org>,
        Christoffer Dall <christoffer.dall@...aro.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Mark Rutland <mark.rutland@....com>,
        Robin Murphy <robin.murphy@....com>,
        Andrew Jones <drjones@...hat.com>,
        Hanjun Guo <guohanjun@...wei.com>,
        Jayachandran C <jnair@...iumnetworks.com>,
        Jon Masters <jcm@...hat.com>,
        Russell King - ARM Linux <linux@...linux.org.uk>
Subject: Re: [PATCH v3 00/18] arm64: Add SMCCC v1.1 support and CVE-2017-5715
 (Spectre variant 2) mitigation

On 1 February 2018 at 11:46, Marc Zyngier <marc.zyngier@....com> wrote:
> ARM has recently published a SMC Calling Convention (SMCCC)
> specification update[1] that provides an optimised calling convention
> and optional, discoverable support for mitigating CVE-2017-5715. ARM
> Trusted Firmware (ATF) has already gained such an implementation[2].
>
> This series addresses a few things:
>
> - It provides a KVM implementation of PSCI v1.0, which is a
>   prerequisite for being able to discover SMCCC v1.1, together with a
>   new userspace API to control the PSCI revision number that the guest
>   sees.
>
> - It allows KVM to advertise SMCCC v1.1, which is de-facto supported
>   already (it never corrupts any of the guest registers).
>
> - It implements KVM support for the ARCH_WORKAROUND_1 function that is
>   used to mitigate CVE-2017-5715 in a guest (if such mitigation is
>   available on the host).
>
> - It implements SMCCC v1.1 and ARCH_WORKAROUND_1 discovery support in
>   the kernel itself.
>
> - It finally provides firmware callbacks for CVE-2017-5715 for both
>   kernel and KVM and drop the initial PSCI_GET_VERSION based
>   mitigation.
>
> Patch 1 is already merged, and included here for reference. Patches on
> top of arm64/for-next/core. Tested on Seattle and Juno, the latter
> with ATF implementing SMCCC v1.1.
>
> [1]: https://developer.arm.com/support/security-update/downloads/
>
> [2]: https://github.com/ARM-software/arm-trusted-firmware/pull/1240
>
> * From v2:
>   - Fixed SMC handling in KVM
>   - PSCI fixes and tidying up
>   - SMCCC primitive rework for better code generation (both efficiency
>   and correctness)
>   - Remove PSCI_GET_VERSION as a mitigation vector
>
> * From v1:
>   - Fixed 32bit build
>   - Fix function number sign extension (Ard)
>   - Inline SMCCC v1.1 primitives (cpp soup)
>   - Prevent SMCCC spamming on feature probing
>   - Random fixes and tidying up
>
> Marc Zyngier (18):
>   arm64: KVM: Fix SMCCC handling of unimplemented SMC/HVC calls
>   arm: KVM: Fix SMCCC handling of unimplemented SMC/HVC calls
>   arm64: KVM: Increment PC after handling an SMC trap
>   arm/arm64: KVM: Consolidate the PSCI include files
>   arm/arm64: KVM: Add PSCI_VERSION helper
>   arm/arm64: KVM: Add smccc accessors to PSCI code
>   arm/arm64: KVM: Implement PSCI 1.0 support
>   arm/arm64: KVM: Add PSCI version selection API
>   arm/arm64: KVM: Advertise SMCCC v1.1
>   arm/arm64: KVM: Turn kvm_psci_version into a static inline
>   arm64: KVM: Report SMCCC_ARCH_WORKAROUND_1 BP hardening support
>   arm64: KVM: Add SMCCC_ARCH_WORKAROUND_1 fast handling
>   firmware/psci: Expose PSCI conduit
>   firmware/psci: Expose SMCCC version through psci_ops
>   arm/arm64: smccc: Make function identifiers an unsigned quantity
>   arm/arm64: smccc: Implement SMCCC v1.1 inline primitive
>   arm64: Add ARM_SMCCC_ARCH_WORKAROUND_1 BP hardening support
>   arm64: Kill PSCI_GET_VERSION as a variant-2 workaround
>

I have given this a spin on my Overdrive, and everything seems to work
as expected, both in the host and in the guest (I single stepped
through the guest to ensure that it gets the expected answer from the
SMCCC feature info call)

Tested-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>