tl;dr: We are fixing things as quickly as we can safely do so. The fixes will be ongoing, keep testing and installing new kernels as they appear! On Sat, Jan 6, 2018 at 1:32 PM, Chris Adams <linux@xxxxxxxxxxx> wrote: > Once upon a time, Adam Williamson <adamwill@xxxxxxxxxxxxxxxxx> said: >> * If the fix does cause problems on your hardware, you can disable it >> by booting with the kernel parameter 'nopti'. > > So, on RHEL/CentOS kernels, there are three new entries in > /sys/kernel/debug/x86; ibpb_enabled, ibrs_enabled, and pti_enabled. I > don't see these on the Fedora kernel. > > Are these variables something added by Red Hat to their kernel, > something that will be added to Fedora, etc.? They are useful to see > exactly what fix(es) are being applied, as well as to have a runtime way > to enable/disable them. These do not exist in Fedora yet. For KPTI, the feature is implemented, but there isn't a debugfs entry. Variant 2 Spectre mitigation has a couple of proposed solutions. IBRS and retpoline are both being discussed upstream, and the end result will likely be a combination of the 2. Unfortunately both have external requirements. Retpoline requires GCC patches, and microcode updates for some CPUs. IBRS requires microcode updates. While RHEL has done quite a bit of testing with IBRS in their kernels, Fedora moves a lot quicker and current Fedora kernels are substantially different from the current RHEL kernels. Additionally, while RHEL was given microcode to ship with these updates, Intel has not released them upstream (soon I am told). It is entirely possible that the patches floating around upstream have not been tested with the microcode that RHEL shipped. Given that variant 2 is difficult (not impossible) to attack, we have been waiting to see what we can ship, when microcode is available and GCC updates are available. I can assure you that I have spending pretty much all of my time tracking upstream, testing patch sets, and doing what I can to make sure we have mitigations for all 3 variants in place as quickly as possible. Today's build of rawhide contains mitigation for variant 1 of spectre and variant 3 (meltdown) for x86_64. Current stable Fedora kernels contain mitigation for meltdown on x86_64 as well. Wednesday should see a new kernel pushed to updates-testing with some bug fixes for the meltdown mitigation (KPTI), and some mitigation for variant 1. I am hoping to also get some meltdown coverage for other architectures in that update. While I would love to see some variant 2 coverage as well, it is unlikely in the Wednesday time frame. If it is possible, I will include those as well, but even then, it will not be the final solution. As soon as a solution is deemed ready, it will be pushed to Fedora. Justin _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx
