On 09/01/2018 13:03, Thomas Gleixner wrote: > On Tue, 9 Jan 2018, Paolo Bonzini wrote: >> On 09/01/2018 11:15, Thomas Gleixner wrote: >>> On Mon, 8 Jan 2018, Paolo Bonzini wrote: >>> >>>> This series allows guests to use the MSR_IA32_SPEC_CTRL and >>>> MSR_IA32_PRED_CMD model specific registers that were added as mitigations >>>> for CVE-2017-5715. >>>> >>>> These are only the KVM specific parts of the fix. It does *not* yet >>>> include any protection for reading host memory from the guest, because >>>> that would be done in the same way as the rest of Linux. So there is no >>>> IBRS *usage* here, no retpolines, no stuffing of the return stack buffer. >>>> (KVM already includes a fix to clear all registers on vmexit, which is >>>> enough to block Google Project Zero's PoC exploit). >>>> >>>> However, I am including the changes to use IBPB (indirect branch >>>> predictor barrier) if available. That occurs only when there is a VCPU >>>> switch on a physical CPU, thus it has a small impact on performance. >>>> >>>> The patches are a bit hackish because the relevant cpufeatures have >>>> not been included yet, and because I wanted to make the patches easier >>>> to backport to distro kernels if desired, but I would still like to >>>> have them in 4.16. > > We really want to coordinate that proper with the ongoing integration of > the IB** for bare metal. Yes, this can get merged to master together with the bare-metal parts. If, as I expect, the -rc rules will be be bent a bit for IB** (and perhaps retpolines too) in 4.16, we have some time to sort it out. Thanks, Paolo > And that stuff really does not need to be hackish at all. We've spent a lot > of effort keeping all of it clean _AND_ available for 4.14 stable > consumption. Everything before 4.9 is a big fricking and incompatible mess > anyway.
