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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Message-ID: <86efm46bcf.wl-marc.zyngier@arm.com>
Date:   Thu, 01 Feb 2018 14:20:00 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
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 Thu, 01 Feb 2018 13:59:45 +0000,
Ard Biesheuvel wrote:
> 
> 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>

Awesome, thanks Ard.

	M.

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