Re: [PATCH v3 0/9] KVM: nSVM: fixes for CR3/MMU switch upon nested guest entry/exit

Paolo Bonzini
2020-07-09T18:01:14Z

On 09/07/20 16:53, Vitaly Kuznetsov wrote:
> This is a successor of "[PATCH v2 0/3] KVM: nSVM: fix #TF from CR3 switch
> when entering guest" and "[PATCH] KVM: x86: drop erroneous mmu_check_root()
> from fast_pgd_switch()".
>
> The snowball is growing fast! It all started with an intention to fix
> the particular 'tripple fault' issue (now fixed by PATCH7) but now we
> also get rid of unconditional kvm_mmu_reset_context() upon nested guest
> entry/exit and make the code resemble nVMX. There is still a huge room
> for further improvement (proper error propagation, removing unconditional
> MMU sync/TLB flush,...) but at least we're making some progress.
>
> Tested with kvm selftests/kvm-unit-tests and by running nested Hyper-V
> on KVM. The series doesn't seem to introduce any new issues.

Looks like a v4 is needed but we're converging at least, it won't have
27 patches. :)

> Vitaly Kuznetsov (9):
> KVM: nSVM: split kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu()
> KVM: nSVM: stop dereferencing vcpu->arch.mmu to get the context in
> kvm_init_shadow{,_npt}_mmu()
> KVM: nSVM: reset nested_run_pending upon nested_svm_vmrun_msrpm()
> failure
> KVM: nSVM: prepare to handle errors from enter_svm_guest_mode()
> KVM: nSVM: introduce nested_svm_load_cr3()
> KVM: nSVM: move kvm_set_cr3() after nested_svm_uninit_mmu_context()
> KVM: nSVM: implement nested_svm_load_cr3() and use it for host->guest
> switch
> KVM: nSVM: use nested_svm_load_cr3() on guest->host switch
> KVM: x86: drop superfluous mmu_check_root() from fast_pgd_switch()
>
> arch/x86/kvm/mmu.h | 3 +-
> arch/x86/kvm/mmu/mmu.c | 39 ++++++++++----
> arch/x86/kvm/svm/nested.c | 108 ++++++++++++++++++++++++++++----------
> arch/x86/kvm/svm/svm.c | 6 ++-
> arch/x86/kvm/svm/svm.h | 4 +-
> 5 files changed, 116 insertions(+), 44 deletions(-)
>