On 05/29/2018 08:11 AM, Marc Zyngier wrote: > This patch series implements the Linux kernel side of the "Spectre-v4" > (CVE-2018-3639) mitigation known as "Speculative Store Bypass Disable" > (SSBD). Looks good, with the exception of the naming in patch 5, and a question about how you're handling live migration of VMs (which needs to preserve mitigation state). Once those are answered I think it's good. > For all released Arm Cortex-A CPUs that are affected by this issue, then > the preferred mitigation is simply to set a chicken bit in the firmware > during CPU initialisation and therefore no change to Linux is required. > Other CPUs may require the chicken bit to be toggled dynamically (for > example, when switching between user-mode and kernel-mode) and this is > achieved by calling into EL3 via an SMC which has been published as part > of the latest SMCCC specification: We're asking (server) silicon vendors that can do so inexpensively to implement both a firmware knob to control the chicken bit and the ATF interface. This allows some users to disable the mitigation if they want to, for example in closed lab environments doing CONFIG_BENCHMARKING comparisons to other arches which might have mitigations disabled. Not that I like that, but I want Arm to be on an equal footing at least ;) Jon. _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
