Messages in this thread Patch in this message |  | | Subject | Re: [PATCH v6 4/4] KVM: nSVM: implement on demand allocation of the nested state | From | Maxim Levitsky <> | Date | Wed, 30 Sep 2020 18:35:40 +0300 |
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On Mon, 2020-09-28 at 22:15 -0700, Sean Christopherson wrote: > On Wed, Sep 23, 2020 at 12:10:25AM +0300, Maxim Levitsky wrote: > > This way we don't waste memory on VMs which don't use nesting > > virtualization even when the host enabled it for them. > > > > Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> > > --- > > arch/x86/kvm/svm/nested.c | 42 ++++++++++++++++++++++++++++++ > > arch/x86/kvm/svm/svm.c | 55 ++++++++++++++++++++++----------------- > > arch/x86/kvm/svm/svm.h | 6 +++++ > > 3 files changed, 79 insertions(+), 24 deletions(-) > > > > diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c > > index 09417f5197410..dd13856818a03 100644 > > --- a/arch/x86/kvm/svm/nested.c > > +++ b/arch/x86/kvm/svm/nested.c > > @@ -467,6 +467,9 @@ int nested_svm_vmrun(struct vcpu_svm *svm) > > > > vmcb12 = map.hva; > > > > + if (WARN_ON(!svm->nested.initialized)) > > Probably should use WARN_ON_ONCE, if this is somehow it, userspace could > easily spam the kernel. Makes sense.
> > Side topic, do we actually need 'initialized'? Wouldn't checking for a > valid nested.msrpm or nested.hsave suffice?
It a matter of taste - I prefer to have a single variable controlling this, rather than two. a WARN_ON(svm->nested.initialized && !svm->nested.msrpm || !svm->nested.hsave)) would probably be nice to have. IMHO I rather leave this like it is if you don't object.
> > > + return 1; > > + > > if (!nested_vmcb_checks(svm, vmcb12)) { > > vmcb12->control.exit_code = SVM_EXIT_ERR; > > vmcb12->control.exit_code_hi = 0; > > @@ -684,6 +687,45 @@ int nested_svm_vmexit(struct vcpu_svm *svm) > > return 0; > > }
Best regards, Maxim Levitsky
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