From mboxrd@z Thu Jan 1 00:00:00 1970 From: guohanjun@huawei.com (Hanjun Guo) Date: Fri, 2 Feb 2018 11:43:49 +0800 Subject: [PATCH v2 16/16] arm64: Add ARM_SMCCC_ARCH_WORKAROUND_1 BP hardening support In-Reply-To: <8183e28a-39e7-e4f0-d704-35a0beb14ef0@arm.com> References: <20180129174559.1866-1-marc.zyngier@arm.com> <20180129174559.1866-17-marc.zyngier@arm.com> <476d111e-6fb0-9bef-2448-a94d0cc03f45@huawei.com> <49853e5e-f093-2e79-1cfb-182f51fcd6a0@arm.com> <501451b6-cc84-e8d3-b7b6-49a7de953976@arm.com> <8183e28a-39e7-e4f0-d704-35a0beb14ef0@arm.com> Message-ID: <7e62d00e-df3b-1fb8-8e5e-83e1cf0e86bf@huawei.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 2018/2/1 16:53, Marc Zyngier wrote: [...] >>>> ... and actually, perhaps it makes sense for the >>>> SMCCC_ARCH_WORKAROUND_1 check to be completely independent of MIDR >>>> based errata matching? >>>> >>>> I.e., if SMCCC v1.1 and SMCCC_ARCH_WORKAROUND_1 are both implemented, >>>> we should probably invoke it even if the MIDR is not known to belong >>>> to an affected implementation. >>> >>> This would have an impact on big-little systems, for which there is >>> often a bunch of unaffected CPUs. >> >> I think it's what we are doing now, SMCCC v1.1 didn't provide the ability >> to report per-cpu SMCCC_ARCH_WORKAROUND_1, and it said: >> - The discovery call must return the same result on all PEs in the system. >> - In heterogeneous systems with some PEs that require mitigation and others >> that do not, the firmware must provide a safe implementation of this >> function on all PEs. >> >> So from the spec that it's the firmware to take care of unaffected CPUs, >> to the kernel it's the same. > > The spec makes it safe. The MIDR list makes it fast. Got it, thank you for clarifying this. Thanks Hanjun