Re: [PATCH] KVM: VMX: Remove proprietary handling of unexpected exit-reasons

[Vitaly Kuznetsov <vkuznets@redhat.com>]

Liran Alon <liran.alon@oracle.com> writes:

> Commit bf653b78f960 ("KVM: vmx: Introduce handle_unexpected_vmexit
> and handle WAITPKG vmexit") introduced proprietary handling of
> specific exit-reasons that should not be raised by CPU because
> KVM configures VMCS such that they should never be raised.
>
> However, since commit 7396d337cfad ("KVM: x86: Return to userspace
> with internal error on unexpected exit reason"), VMX & SVM
> exit handlers were modified to generically handle all unexpected
> exit-reasons by returning to userspace with internal error.
>
> Therefore, there is no need for proprietary handling of specific
> unexpected exit-reasons (This proprietary handling also introduced
> inconsistency for these exit-reasons to silently skip guest instruction
> instead of return to userspace on internal-error).
>
> Fixes: bf653b78f960 ("KVM: vmx: Introduce handle_unexpected_vmexit and handle WAITPKG vmexit")
>
> Signed-off-by: Liran Alon <liran.alon@oracle.com>

(It's been awhile since in software world the word 'proprietary' became
an opposite of free/open-source to me so I have to admit your subject
line really got me interested :-)

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>

> ---
>  arch/x86/kvm/vmx/vmx.c | 12 ------------
>  1 file changed, 12 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index d4575ffb3cec..e31317fc8c95 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -5538,14 +5538,6 @@ static int handle_encls(struct kvm_vcpu *vcpu)
>  	return 1;
>  }
>  
> -static int handle_unexpected_vmexit(struct kvm_vcpu *vcpu)
> -{
> -	kvm_skip_emulated_instruction(vcpu);
> -	WARN_ONCE(1, "Unexpected VM-Exit Reason = 0x%x",
> -		vmcs_read32(VM_EXIT_REASON));
> -	return 1;
> -}
> -
>  /*
>   * The exit handlers return 1 if the exit was handled fully and guest execution
>   * may resume.  Otherwise they set the kvm_run parameter to indicate what needs
> @@ -5597,15 +5589,11 @@ static int (*kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = {
>  	[EXIT_REASON_INVVPID]                 = handle_vmx_instruction,
>  	[EXIT_REASON_RDRAND]                  = handle_invalid_op,
>  	[EXIT_REASON_RDSEED]                  = handle_invalid_op,
> -	[EXIT_REASON_XSAVES]                  = handle_unexpected_vmexit,
> -	[EXIT_REASON_XRSTORS]                 = handle_unexpected_vmexit,
>  	[EXIT_REASON_PML_FULL]		      = handle_pml_full,
>  	[EXIT_REASON_INVPCID]                 = handle_invpcid,
>  	[EXIT_REASON_VMFUNC]		      = handle_vmx_instruction,
>  	[EXIT_REASON_PREEMPTION_TIMER]	      = handle_preemption_timer,
>  	[EXIT_REASON_ENCLS]		      = handle_encls,
> -	[EXIT_REASON_UMWAIT]                  = handle_unexpected_vmexit,
> -	[EXIT_REASON_TPAUSE]                  = handle_unexpected_vmexit,
>  };
>  
>  static const int kvm_vmx_max_exit_handlers =

-- 
Vitaly