On 30/01/2018 12:45, Thomas Gleixner wrote: > On Tue, 30 Jan 2018, David Woodhouse wrote: > >> On Tue, 2018-01-30 at 08:57 -0800, Jim Mattson wrote: >>> It's really hard to tell which patches are being proposed for which >>> repositories, but assuming that everything else is correct, I don't >>> think your condition is adequate. What if the physical CPU and the >>> virtual CPU both have CPUID.(EAX=7H,ECX=0):EDX[26], but only the >>> physical CPU has CPUID.(EAX=7H,ECX=0):EDX[27]? If the guest has write >>> access to MSR_IA32_SPEC_CTRL, it can set MSR_IA32_SPEC_CTRL[1] >>> (STIBP), even though setting that bit in the guest should raise #GP. >> >> Everything we're talking about here is for tip/x86/pti. Which I note >> has just updated to be 4.15-based, although I thought it was going to >> stay on 4.14 for now. So I've updated my tree at >> http://git.infradead.org/linux-retpoline.git/shortlog/refs/heads/ibpb >> accordingly. > > Yes, we tried to stay on 4.14 base but this started to created nasty merge > conflicts for no value. Merging in v4.15 turned out to resolve those issues > while still serving as the feed branch for Gregs stable work. For the time > being we try to make stable backporting at least for 4.14/15 as painless as > possible. Great, then the "per-VCPU MSR bitmaps" branch (git://git.kernel.org/pub/scm/virt/kvm/kvm.git refs/heads/msr-bitmaps) that I created last weekend can be pulled directly in tip/x86/pti. It cherry-picks directly to both 4.14 so it will be fine for Greg too. Paolo
