Messages in this thread |  | | Subject | Re: [PATCH 34/35] x86/kvm: Add IBPB support | From | Paolo Bonzini <> | Date | Fri, 19 Jan 2018 17:48:15 +0100 |
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On 19/01/2018 17:08, David Woodhouse wrote: > On Fri, 2018-01-19 at 16:25 +0100, Paolo Bonzini wrote: >> Without retpolines, KVM userspace is not protected from the guest >> poisoning the BTB, because there is no IBRS-barrier on the vmexit >> path. >> So there are two more IBPBs that are needed if retpolines are >> enabled: >> >> 1) in kvm_sched_out >> >> 2) at the end of vcpu_run > > Hm, yes. That does seem reasonable. Can we make it conditional so it > only happens *if* we end up back in userspace, and not for a VM-> > kernel->VM transition?
We can/want/must. It's actually kvm_arch_vcpu_ioctl_run, not vcpu_run. Sorry.
> And can I have a patch against > http://git.infradead.org/users/dwmw2/linux-retpoline.git/shortlog/refs/heads/ibpb-upstream > please (see the XX in that top commit too). > > I'm still putting that together, and the IBRS bits on top; getting on > an airplane to spend some more quality time with it now...
I'm completely lost with all the branches...
Paolo
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