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

[Vitaly Kuznetsov <vkuznets@redhat.com>]

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,

hv_inject_synthetic_vmexit_post_tlb_flush()

seems to be accurate.

-- 
Vitaly