Re: [PATCH v3 14/34] KVM: x86: Introduce .post_hv_l2_tlb_flush() nested hook

Maxim Levitsky
2022-05-18T12:50:02Z

On Wed, 2022-05-18 at 14:43 +0200, Vitaly Kuznetsov wrote:
> Maxim Levitsky <mlevitsk@redhat.com> writes:
>
> > On Thu, 2022-04-14 at 15:19 +0200, Vitaly Kuznetsov wrote:
> > > Hyper-V supports injecting synthetic L2->L1 exit after performing
> > > L2 TLB flush operation but the procedure is vendor specific.
> > > Introduce .post_hv_l2_tlb_flush() nested hook for it.
> > >
> > > Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> > > ---
> > > arch/x86/include/asm/kvm_host.h | 1 +
> > > arch/x86/kvm/Makefile | 3 ++-
> > > arch/x86/kvm/svm/hyperv.c | 11 +++++++++++
> > > arch/x86/kvm/svm/hyperv.h | 2 ++
> > > arch/x86/kvm/svm/nested.c | 1 +
> > > arch/x86/kvm/vmx/evmcs.c | 4 ++++
> > > arch/x86/kvm/vmx/evmcs.h | 1 +
> > > arch/x86/kvm/vmx/nested.c | 1 +
> > > 8 files changed, 23 insertions(+), 1 deletion(-)
> > > create mode 100644 arch/x86/kvm/svm/hyperv.c
> > >
> > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > > index 8b2a52bf26c0..ce62fde5f4ff 100644
> > > --- a/arch/x86/include/asm/kvm_host.h
> > > +++ b/arch/x86/include/asm/kvm_host.h
> > > @@ -1558,6 +1558,7 @@ struct kvm_x86_nested_ops {
> > > int (*enable_evmcs)(struct kvm_vcpu *vcpu,
> > > uint16_t *vmcs_version);
> > > uint16_t (*get_evmcs_version)(struct kvm_vcpu *vcpu);
> > > + void (*post_hv_l2_tlb_flush)(struct kvm_vcpu *vcpu);
> > > };
> > >
> > > struct kvm_x86_init_ops {
> > > diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
> > > index 30f244b64523..b6d53b045692 100644
> > > --- a/arch/x86/kvm/Makefile
> > > +++ b/arch/x86/kvm/Makefile
> > > @@ -25,7 +25,8 @@ kvm-intel-y += vmx/vmx.o vmx/vmenter.o vmx/pmu_intel.o vmx/vmcs12.o \
> > > vmx/evmcs.o vmx/nested.o vmx/posted_intr.o
> > > kvm-intel-$(CONFIG_X86_SGX_KVM) += vmx/sgx.o
> > >
> > > -kvm-amd-y += svm/svm.o svm/vmenter.o svm/pmu.o svm/nested.o svm/avic.o svm/sev.o
> > > +kvm-amd-y += svm/svm.o svm/vmenter.o svm/pmu.o svm/nested.o svm/avic.o \
> > > + svm/sev.o svm/hyperv.o
> > >
> > > ifdef CONFIG_HYPERV
> > > kvm-amd-y += svm/svm_onhyperv.o
> > > diff --git a/arch/x86/kvm/svm/hyperv.c b/arch/x86/kvm/svm/hyperv.c
> > > new file mode 100644
> > > index 000000000000..c0749fc282fe
> > > --- /dev/null
> > > +++ b/arch/x86/kvm/svm/hyperv.c
> > > @@ -0,0 +1,11 @@
> > > +// SPDX-License-Identifier: GPL-2.0-only
> > > +/*
> > > + * AMD SVM specific code for Hyper-V on KVM.
> > > + *
> > > + * Copyright 2022 Red Hat, Inc. and/or its affiliates.
> > > + */
> > > +#include "hyperv.h"
> > > +
> > > +void svm_post_hv_l2_tlb_flush(struct kvm_vcpu *vcpu)
> > > +{
> > > +}
> > > diff --git a/arch/x86/kvm/svm/hyperv.h b/arch/x86/kvm/svm/hyperv.h
> > > index 8cf702fed7e5..a2b0d7580b0d 100644
> > > --- a/arch/x86/kvm/svm/hyperv.h
> > > +++ b/arch/x86/kvm/svm/hyperv.h
> > > @@ -48,4 +48,6 @@ static inline void nested_svm_hv_update_vm_vp_ids(struct kvm_vcpu *vcpu)
> > > hv_vcpu->nested.vp_id = hve->hv_vp_id;
> > > }
> > >
> > > +void svm_post_hv_l2_tlb_flush(struct kvm_vcpu *vcpu);
> > > +
> > > #endif /* __ARCH_X86_KVM_SVM_HYPERV_H__ */
> > > diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> > > index 2d1a76343404..de3f27301b5c 100644
> > > --- a/arch/x86/kvm/svm/nested.c
> > > +++ b/arch/x86/kvm/svm/nested.c
> > > @@ -1665,4 +1665,5 @@ struct kvm_x86_nested_ops svm_nested_ops = {
> > > .get_nested_state_pages = svm_get_nested_state_pages,
> > > .get_state = svm_get_nested_state,
> > > .set_state = svm_set_nested_state,
> > > + .post_hv_l2_tlb_flush = svm_post_hv_l2_tlb_flush,
> > > };
> > > diff --git a/arch/x86/kvm/vmx/evmcs.c b/arch/x86/kvm/vmx/evmcs.c
> > > index 87e3dc10edf4..e390e67496df 100644
> > > --- a/arch/x86/kvm/vmx/evmcs.c
> > > +++ b/arch/x86/kvm/vmx/evmcs.c
> > > @@ -437,3 +437,7 @@ int nested_enable_evmcs(struct kvm_vcpu *vcpu,
> > >
> > > return 0;
> > > }
> > > +
> > > +void vmx_post_hv_l2_tlb_flush(struct kvm_vcpu *vcpu)
> > > +{
> > > +}
> > > diff --git a/arch/x86/kvm/vmx/evmcs.h b/arch/x86/kvm/vmx/evmcs.h
> > > index 8d70f9aea94b..b120b0ead4f3 100644
> > > --- a/arch/x86/kvm/vmx/evmcs.h
> > > +++ b/arch/x86/kvm/vmx/evmcs.h
> > > @@ -244,5 +244,6 @@ int nested_enable_evmcs(struct kvm_vcpu *vcpu,
> > > uint16_t *vmcs_version);
> > > void nested_evmcs_filter_control_msr(u32 msr_index, u64 *pdata);
> > > int nested_evmcs_check_controls(struct vmcs12 *vmcs12);
> > > +void vmx_post_hv_l2_tlb_flush(struct kvm_vcpu *vcpu);
> > >
> > > #endif /* __KVM_X86_VMX_EVMCS_H */
> > > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> > > index ee88921c6156..cc6c944b5815 100644
> > > --- a/arch/x86/kvm/vmx/nested.c
> > > +++ b/arch/x86/kvm/vmx/nested.c
> > > @@ -6850,4 +6850,5 @@ struct kvm_x86_nested_ops vmx_nested_ops = {
> > > .write_log_dirty = nested_vmx_write_pml_buffer,
> > > .enable_evmcs = nested_enable_evmcs,
> > > .get_evmcs_version = nested_get_evmcs_version,
> > > + .post_hv_l2_tlb_flush = vmx_post_hv_l2_tlb_flush,
> > > };
> >
> > I think that the name of the function is misleading, since it is not called
> > after each L2 HV tlb flush, but only after a flush which needs to inject
> > that synthetic VM exit.
> >
> > I think something like 'inject_synthetic_l2_hv_tlb_flush_vmexit'
> > (not a good name IMHO, but you get the idea) would be better.
> >
>
> Naming is hard indeed,

Indeed :-)

https://www.monkeyuser.com/2019/_/

>
> hv_inject_synthetic_vmexit_post_tlb_flush()

Looks great!

Best regards,
Maxim Levitsky

>
> seems to be accurate.
>