This patch series implements multiple mitigations for the speculative execution findings: 1. The definition of the gmb() barrier as currently used by the distributions, we may have to find a better name for it 2. The architecture code for the nospec interfaces, the macros for nospec_ptr and nospec_load just use the gmb() barrier 3. The enablement for firmware features to switch between different branch prediction modes. It comes with a config option CONFIG_KERNEL_NOBP, two new kernel parameters "nobp=[0|1]" and "nospec", and a new system call s390_modify_bp. With CONFIG_KERNEL_NOBP=y the new branch prediction mode is active for the kernel code by default and can be switched off with "nospec" or "nobp=0". With CONFIG_KERNEL_NOBP=n the new mode is inactive for kernel code unless "nobp=1" is specified. User space code can use the trapdoor system call s390_modify_bp to set the new TIF_NOBP bit. This switches to the new branch prediction mode for the lifetime of the task, any children of the task will inherit this attribute. The vCPU of a KVM guest will run with the new branch prediction mode if either the associated qemu task has TIF_NOBP set or if the KVM kernel code sets TIF_NOBP_GUEST. The later will require a small update to KVM backend. 4. Transport channel reduction by clearing registers on interrupts, system calls and KVM guest exits. We are working on an equivalent for retpoline, stay tuned. @Greg: I have started with the backports for the stable kernel releases, but unless the interface for gmp/nospec_ptr/nospec_load is cast in stone does it make sense to send them? Christian Borntraeger (1): KVM: s390: wire up seb feature Martin Schwidefsky (5): s390/alternative: use a copy of the facility bit mask s390: implement nospec_[load|ptr] s390: add options to change branch prediction behaviour for the kernel s390: add system call to run tasks with modified branch prediction s390: scrub registers on kernel entry and KVM exit arch/s390/Kconfig | 17 +++++ arch/s390/include/asm/barrier.h | 38 ++++++++++ arch/s390/include/asm/facility.h | 18 +++++ arch/s390/include/asm/kvm_host.h | 3 +- arch/s390/include/asm/lowcore.h | 3 +- arch/s390/include/asm/processor.h | 1 + arch/s390/include/asm/thread_info.h | 4 ++ arch/s390/include/uapi/asm/kvm.h | 4 +- arch/s390/include/uapi/asm/unistd.h | 3 +- arch/s390/kernel/alternative.c | 33 ++++++++- arch/s390/kernel/early.c | 5 ++ arch/s390/kernel/entry.S | 134 +++++++++++++++++++++++++++++++++++- arch/s390/kernel/ipl.c | 1 + arch/s390/kernel/setup.c | 4 +- arch/s390/kernel/smp.c | 6 +- arch/s390/kernel/sys_s390.c | 8 +++ arch/s390/kernel/syscalls.S | 1 + arch/s390/kvm/kvm-s390.c | 11 +++ arch/s390/kvm/vsie.c | 8 +++ include/uapi/linux/kvm.h | 1 + 20 files changed, 294 insertions(+), 9 deletions(-) -- 2.7.4
