From: Marc Zyngier <marc.zyngier@arm.com> To: Hanjun Guo <guohanjun@huawei.com>, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu Cc: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will.deacon@arm.com>, Peter Maydell <peter.maydell@linaro.org>, Christoffer Dall <christoffer.dall@linaro.org>, Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>, Mark Rutland <mark.rutland@arm.com>, Robin Murphy <robin.murphy@arm.com>, Ard Biesheuvel <ard.biesheuvel@linaro.org>, Jon Masters <jcm@redhat.com> Subject: Re: [PATCH v2 16/16] arm64: Add ARM_SMCCC_ARCH_WORKAROUND_1 BP hardening support Date: Wed, 31 Jan 2018 14:11:06 +0000 [thread overview] Message-ID: <49853e5e-f093-2e79-1cfb-182f51fcd6a0@arm.com> (raw) In-Reply-To: <476d111e-6fb0-9bef-2448-a94d0cc03f45@huawei.com> On 31/01/18 13:56, Hanjun Guo wrote: > Hi Marc, > > On 2018/1/30 1:45, Marc Zyngier wrote: >> static int enable_psci_bp_hardening(void *data) >> { >> const struct arm64_cpu_capabilities *entry = data; >> >> - if (psci_ops.get_version) >> + if (psci_ops.get_version) { >> + if (check_smccc_arch_workaround_1(entry)) >> + return 0; > > If I'm using the new version SMCCC, the firmware have the choice to decide > whether this machine needs the workaround, even if the CPU is vulnerable > for CVE-2017-5715, but.. > >> + >> install_bp_hardening_cb(entry, >> (bp_hardening_cb_t)psci_ops.get_version, >> __psci_hyp_bp_inval_start, >> __psci_hyp_bp_inval_end); > > ..the code above seems will enable get_psci_version() for CPU and will > trap to trust firmware even the new version of firmware didn't say > we need the workaround, did I understand it correctly? Well, you only get there if we've established that your CPU is affected (it has an entry matching its MIDR with the HARDEN_BRANCH_PREDICTOR capability), and that entry points to enable_psci_bp_hardening. It is not the firmware that decides whether we need hardening, but the kernel. The firmware merely provides a facility to apply the hardening. > I'm ask this because some platform will not expose to users to > take advantage of CVE-2017-5715, and we can use different firmware > to report we need such workaround or not, then use a single kernel > image for both vulnerable platforms and no vulnerable ones. You cannot have your cake and eat it. If you don't want to workaround the issue, you can disable the hardening. But asking for the same kernel to do both depending on what the firmware reports doesn't make much sense to me. Thanks, M. -- Jazz is not dead. It just smells funny...
WARNING: multiple messages have this Message-ID (diff)
From: marc.zyngier@arm.com (Marc Zyngier) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v2 16/16] arm64: Add ARM_SMCCC_ARCH_WORKAROUND_1 BP hardening support Date: Wed, 31 Jan 2018 14:11:06 +0000 [thread overview] Message-ID: <49853e5e-f093-2e79-1cfb-182f51fcd6a0@arm.com> (raw) In-Reply-To: <476d111e-6fb0-9bef-2448-a94d0cc03f45@huawei.com> On 31/01/18 13:56, Hanjun Guo wrote: > Hi Marc, > > On 2018/1/30 1:45, Marc Zyngier wrote: >> static int enable_psci_bp_hardening(void *data) >> { >> const struct arm64_cpu_capabilities *entry = data; >> >> - if (psci_ops.get_version) >> + if (psci_ops.get_version) { >> + if (check_smccc_arch_workaround_1(entry)) >> + return 0; > > If I'm using the new version SMCCC, the firmware have the choice to decide > whether this machine needs the workaround, even if the CPU is vulnerable > for CVE-2017-5715, but.. > >> + >> install_bp_hardening_cb(entry, >> (bp_hardening_cb_t)psci_ops.get_version, >> __psci_hyp_bp_inval_start, >> __psci_hyp_bp_inval_end); > > ..the code above seems will enable get_psci_version() for CPU and will > trap to trust firmware even the new version of firmware didn't say > we need the workaround, did I understand it correctly? Well, you only get there if we've established that your CPU is affected (it has an entry matching its MIDR with the HARDEN_BRANCH_PREDICTOR capability), and that entry points to enable_psci_bp_hardening. It is not the firmware that decides whether we need hardening, but the kernel. The firmware merely provides a facility to apply the hardening. > I'm ask this because some platform will not expose to users to > take advantage of CVE-2017-5715, and we can use different firmware > to report we need such workaround or not, then use a single kernel > image for both vulnerable platforms and no vulnerable ones. You cannot have your cake and eat it. If you don't want to workaround the issue, you can disable the hardening. But asking for the same kernel to do both depending on what the firmware reports doesn't make much sense to me. Thanks, M. -- Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2018-01-31 14:11 UTC|newest] Thread overview: 116+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-01-29 17:45 [PATCH v2 00/16] arm64: Add SMCCC v1.1 support and CVE-2017-5715 (Spectre variant 2) mitigation Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 17:45 ` [PATCH v2 01/16] arm64: KVM: Fix SMCCC handling of unimplemented SMC/HVC calls Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 17:45 ` [PATCH v2 02/16] arm: " Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 17:45 ` [PATCH v2 03/16] arm/arm64: KVM: Consolidate the PSCI include files Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 17:45 ` [PATCH v2 04/16] arm/arm64: KVM: Add PSCI_VERSION helper Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-30 13:15 ` Robin Murphy 2018-01-30 13:15 ` Robin Murphy 2018-01-30 14:52 ` Marc Zyngier 2018-01-30 14:52 ` Marc Zyngier 2018-01-29 17:45 ` [PATCH v2 05/16] arm/arm64: KVM: Add smccc accessors to PSCI code Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 17:45 ` [PATCH v2 06/16] arm/arm64: KVM: Implement PSCI 1.0 support Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 17:45 ` [PATCH v2 07/16] arm/arm64: KVM: Add PSCI version selection API Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-31 17:38 ` Andrew Jones 2018-01-31 17:38 ` Andrew Jones 2018-01-31 17:45 ` Marc Zyngier 2018-01-31 17:45 ` Marc Zyngier 2018-01-31 18:03 ` Andrew Jones 2018-01-31 18:03 ` Andrew Jones 2018-01-31 18:03 ` Andrew Jones 2018-01-31 18:36 ` Marc Zyngier 2018-01-31 18:36 ` Marc Zyngier 2018-01-31 19:15 ` Andrew Jones 2018-01-31 19:15 ` Andrew Jones 2018-01-31 18:11 ` kbuild test robot 2018-01-31 18:11 ` kbuild test robot 2018-01-29 17:45 ` [PATCH v2 08/16] arm/arm64: KVM: Advertise SMCCC v1.1 Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-30 0:23 ` Russell King - ARM Linux 2018-01-30 0:23 ` Russell King - ARM Linux 2018-01-30 12:28 ` Marc Zyngier 2018-01-30 12:28 ` Marc Zyngier 2018-01-30 12:28 ` Marc Zyngier 2018-01-29 17:45 ` [PATCH v2 09/16] arm/arm64: KVM: Turn kvm_psci_version into a static inline Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 17:45 ` [PATCH v2 10/16] arm64: KVM: Report SMCCC_ARCH_WORKAROUND_1 BP hardening support Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-30 12:38 ` Robin Murphy 2018-01-30 12:38 ` Robin Murphy 2018-01-29 17:45 ` [PATCH v2 11/16] arm64: KVM: Add SMCCC_ARCH_WORKAROUND_1 fast handling Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 17:45 ` [PATCH v2 12/16] firmware/psci: Expose PSCI conduit Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 17:55 ` Lorenzo Pieralisi 2018-01-29 17:55 ` Lorenzo Pieralisi 2018-01-29 17:45 ` [PATCH v2 13/16] firmware/psci: Expose SMCCC version through psci_ops Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 18:39 ` Lorenzo Pieralisi 2018-01-29 18:39 ` Lorenzo Pieralisi 2018-01-30 12:09 ` Marc Zyngier 2018-01-30 12:09 ` Marc Zyngier 2018-01-30 12:55 ` Robin Murphy 2018-01-30 12:55 ` Robin Murphy 2018-01-30 13:51 ` Marc Zyngier 2018-01-30 13:51 ` Marc Zyngier 2018-01-29 17:45 ` [PATCH v2 14/16] arm/arm64: smccc: Make function identifiers an unsigned quantity Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 17:45 ` [PATCH v2 15/16] arm/arm64: smccc: Implement SMCCC v1.1 inline primitive Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 19:07 ` Robin Murphy 2018-01-29 19:07 ` Robin Murphy 2018-01-30 8:54 ` Marc Zyngier 2018-01-30 8:54 ` Marc Zyngier 2018-01-29 21:45 ` Ard Biesheuvel 2018-01-29 21:45 ` Ard Biesheuvel 2018-01-30 12:27 ` Marc Zyngier 2018-01-30 12:27 ` Marc Zyngier 2018-01-30 12:29 ` Ard Biesheuvel 2018-01-30 12:29 ` Ard Biesheuvel 2018-01-30 12:29 ` Ard Biesheuvel 2018-01-29 17:45 ` [PATCH v2 16/16] arm64: Add ARM_SMCCC_ARCH_WORKAROUND_1 BP hardening support Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 17:45 ` Marc Zyngier 2018-01-29 19:41 ` Ard Biesheuvel 2018-01-29 19:41 ` Ard Biesheuvel 2018-01-30 12:10 ` Marc Zyngier 2018-01-30 12:10 ` Marc Zyngier 2018-01-31 13:56 ` Hanjun Guo 2018-01-31 13:56 ` Hanjun Guo 2018-01-31 13:56 ` Hanjun Guo 2018-01-31 14:11 ` Marc Zyngier [this message] 2018-01-31 14:11 ` Marc Zyngier 2018-01-31 14:35 ` Ard Biesheuvel 2018-01-31 14:35 ` Ard Biesheuvel 2018-01-31 14:38 ` Ard Biesheuvel 2018-01-31 14:38 ` Ard Biesheuvel 2018-01-31 15:05 ` Marc Zyngier 2018-01-31 15:05 ` Marc Zyngier 2018-02-01 2:40 ` Hanjun Guo 2018-02-01 2:40 ` Hanjun Guo 2018-02-01 6:52 ` Hanjun Guo 2018-02-01 6:52 ` Hanjun Guo 2018-02-01 6:52 ` Hanjun Guo 2018-02-01 8:53 ` Marc Zyngier 2018-02-01 8:53 ` Marc Zyngier 2018-02-02 3:43 ` Hanjun Guo 2018-02-02 3:43 ` Hanjun Guo 2018-06-09 13:22 ` [PATCH v2 00/16] arm64: Add SMCCC v1.1 support and CVE-2017-5715 (Spectre variant 2) mitigation Jon Masters 2018-06-09 13:22 ` Jon Masters 2018-06-09 14:06 ` Marc Zyngier 2018-06-09 14:06 ` Marc Zyngier 2018-06-09 14:06 ` Marc Zyngier
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