Messages in this thread | | | Subject | Re: [PATCH v2] KVM: Expose the split lock detection feature to guest VM | From | Paolo Bonzini <> | Date | Wed, 4 Jul 2018 18:21:01 +0200 |
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On 04/07/2018 16:51, Thomas Gleixner wrote: > There is no rush for this to be in KVM/QEMU now because all what exists for > this new split lock thing is 'silicon' running on an emulator. And w/o > support in the kernel proper this is completely useless.
That's good. I assumed it was IceLake, in which case the feature would block the definition of a standard IceLake CPU model in QEMU.
> So this needs the following things: > > 1) Proper enumeration via CPUID or MISC_FEATURES. The current detection > hack is just broken.
Yes please.
> 2) A proper host side implementation, which then automatically makes the > stuff usable in a guest once it is exposed.
If the CPUID bit or MISC_FEATURES is added, you don't even need the host side for the guests to use it. It's only needed now because of the ugly MSR-based detection.
> 3) A proper way how to expose MSR_TEST_CTL to the guest, but surely not > with extra split_lock_ctrl voodoo. It's an MSR nothing else. KVM/QEMU > have standartized ways to deal with MSRs and the required selective > bitwise access control.
That part is pretty much standard, I'm not worried about it. We have one variable in struct kvm_vcpu_arch for each MSR (or set of MSRs) that we expose, so that's the split_lock_ctrl voodoo. :)
Once the detection is sorted out, KVM is easy.
Paolo
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