linux-kernel - Re: [PATCH 09/21] KVM: VMX: Modify NMI and INTR handlers to take intr

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Date: Tue, 12 Mar 2024 14:43:07 +1300
From: "Huang, Kai" <kai.huang@...el.com>
To: Paolo Bonzini <pbonzini@...hat.com>, <linux-kernel@...r.kernel.org>,
	<kvm@...r.kernel.org>
CC: <seanjc@...gle.com>, <michael.roth@....com>, <isaku.yamahata@...el.com>,
	<thomas.lendacky@....com>
Subject: Re: [PATCH 09/21] KVM: VMX: Modify NMI and INTR handlers to take
 intr_info as function argument



On 28/02/2024 12:20 pm, Paolo Bonzini wrote:
> From: Sean Christopherson <seanjc@...gle.com>
> 
> TDX uses different ABI to get information about VM exit.  Pass intr_info to
> the NMI and INTR handlers instead of pulling it from vcpu_vmx in
> preparation for sharing the bulk of the handlers with TDX.
> 
> When the guest TD exits to VMM, RAX holds status and exit reason, RCX holds
> exit qualification etc rather than the VMCS fields because VMM doesn't have
> access to the VMCS.  

IMHO this can be simpler:

TDX conveys VM exit information via GPRs while normal VMX does via VMCS 
fields.

The eventual code will be
> 
> VMX:
>    - get exit reason, intr_info, exit_qualification, and etc from VMCS
>    - call NMI/INTR handlers (common code)
> 
> TDX:
>    - get exit reason, intr_info, exit_qualification, and etc from guest
>      registers
>    - call NMI/INTR handlers (common code)

It's kinda nicer to mention why to change handle_exception_irqoff()'s 
first argument from @vmx to @vcpu.

Anyway, doesn't matter ...

> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>
> Message-Id: <0396a9ae70d293c9d0b060349dae385a8a4fbcec.1705965635.git.isaku.yamahata@...el.com>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>

.. Acked-by: Kai Huang <kai.huang@...el.com>

> ---
>   arch/x86/kvm/vmx/vmx.c | 16 +++++++---------
>   1 file changed, 7 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 3d8a7e4c8e37..8aedfe0fd78c 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7000,24 +7000,22 @@ static void handle_nm_fault_irqoff(struct kvm_vcpu *vcpu)
>   		rdmsrl(MSR_IA32_XFD_ERR, vcpu->arch.guest_fpu.xfd_err);
>   }
>   
> -static void handle_exception_irqoff(struct vcpu_vmx *vmx)
> +static void handle_exception_irqoff(struct kvm_vcpu *vcpu, u32 intr_info)
>   {
> -	u32 intr_info = vmx_get_intr_info(&vmx->vcpu);
> -
>   	/* if exit due to PF check for async PF */
>   	if (is_page_fault(intr_info))
> -		vmx->vcpu.arch.apf.host_apf_flags = kvm_read_and_reset_apf_flags();
> +		vcpu->arch.apf.host_apf_flags = kvm_read_and_reset_apf_flags();
>   	/* if exit due to NM, handle before interrupts are enabled */
>   	else if (is_nm_fault(intr_info))
> -		handle_nm_fault_irqoff(&vmx->vcpu);
> +		handle_nm_fault_irqoff(vcpu);
>   	/* Handle machine checks before interrupts are enabled */
>   	else if (is_machine_check(intr_info))
>   		kvm_machine_check();
>   }
>   
> -static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu)
> +static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu,
> +					     u32 intr_info)
>   {
> -	u32 intr_info = vmx_get_intr_info(vcpu);
>   	unsigned int vector = intr_info & INTR_INFO_VECTOR_MASK;
>   	gate_desc *desc = (gate_desc *)host_idt_base + vector;
>   
> @@ -7040,9 +7038,9 @@ void vmx_handle_exit_irqoff(struct kvm_vcpu *vcpu)
>   		return;
>   
>   	if (vmx->exit_reason.basic == EXIT_REASON_EXTERNAL_INTERRUPT)
> -		handle_external_interrupt_irqoff(vcpu);
> +		handle_external_interrupt_irqoff(vcpu, vmx_get_intr_info(vcpu));
>   	else if (vmx->exit_reason.basic == EXIT_REASON_EXCEPTION_NMI)
> -		handle_exception_irqoff(vmx);
> +		handle_exception_irqoff(vcpu, vmx_get_intr_info(vcpu));
>   }
>   
>   /*