linux-kernel - Re: [PATCH v5 18/19] KVM:nVMX: Refine error code injection to nested VM

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Date:   Fri, 4 Aug 2023 14:38:04 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Yang Weijiang <weijiang.yang@...el.com>
Cc:     pbonzini@...hat.com, peterz@...radead.org, john.allen@....com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        rick.p.edgecombe@...el.com, chao.gao@...el.com,
        binbin.wu@...ux.intel.com
Subject: Re: [PATCH v5 18/19] KVM:nVMX: Refine error code injection to nested VM

This is not "refinement", this is full on supporting a new nVMX feature.  Please
phrase the shortlog accordingly, e.g. something like this (it's not very good,
but it's a start).

  KVM: nVMX: Add support for exposing "No PM H/W error code checks" to L1

Regarding shortlog, please update all of them in this series to put a space after
the colon, i.e. "KVM: VMX:" and "KVM: x86:", not "KVM:x86:".

>  static void nested_vmx_setup_cr_fixed(struct nested_vmx_msrs *msrs)
> diff --git a/arch/x86/kvm/vmx/nested.h b/arch/x86/kvm/vmx/nested.h
> index 96952263b029..1884628294e4 100644
> --- a/arch/x86/kvm/vmx/nested.h
> +++ b/arch/x86/kvm/vmx/nested.h
> @@ -284,6 +284,13 @@ static inline bool nested_cr4_valid(struct kvm_vcpu *vcpu, unsigned long val)
>  	       __kvm_is_valid_cr4(vcpu, val);
>  }
>  
> +static inline bool nested_cpu_has_no_hw_errcode(struct kvm_vcpu *vcpu)
> +{
> +	struct vcpu_vmx *vmx = to_vmx(vcpu);
> +
> +	return vmx->nested.msrs.basic & VMX_BASIC_NO_HW_ERROR_CODE;

The "CC" part of my suggestion is critical to this being sane.  As is, this reads
"nested CPU has no hardware error code", which is not even remotely close to the
truth.

static inline bool nested_cpu_has_no_hw_errcode_cc(struct kvm_vcpu *vcpu)
{
	return to_vmx(vcpu)->nested.msrs.basic & VMX_BASIC_NO_HW_ERROR_CODE_CC;
}

[*] https://lore.kernel.org/all/ZJ7vyBw1nbTBOfuf@google.com