Re: [PATCH 24/30] nVMX: Correct handling of idt vectoring info

[Avi Kivity <avi@redhat.com>]

On 05/08/2011 11:27 AM, Nadav Har'El wrote:
> This patch adds correct handling of IDT_VECTORING_INFO_FIELD for the nested
> case.
>
> When a guest exits while handling an interrupt or exception, we get this
> information in IDT_VECTORING_INFO_FIELD in the VMCS. When L2 exits to L1,
> there's nothing we need to do, because L1 will see this field in vmcs12, and
> handle it itself. However, when L2 exits and L0 handles the exit itself and
> plans to return to L2, L0 must inject this event to L2.
>
> In the normal non-nested case, the idt_vectoring_info case is discovered after
> the exit, and the decision to inject (though not the injection itself) is made
> at that point. However, in the nested case a decision of whether to return
> to L2 or L1 also happens during the injection phase (see the previous
> patches), so in the nested case we can only decide what to do about the
> idt_vectoring_info right after the injection, i.e., in the beginning of
> vmx_vcpu_run, which is the first time we know for sure if we're staying in
> L2 (i.e., nested_mode is true).
>
> +static void nested_handle_valid_idt_vectoring_info(struct vcpu_vmx *vmx)
> +{
> +	int irq  = vmx->idt_vectoring_info&  VECTORING_INFO_VECTOR_MASK;
> +	int type = vmx->idt_vectoring_info&  VECTORING_INFO_TYPE_MASK;
> +	int errCodeValid = vmx->idt_vectoring_info&
> +		VECTORING_INFO_DELIVER_CODE_MASK;

Innovative coding style.

> +	vmcs_write32(VM_ENTRY_INTR_INFO_FIELD,
> +		irq | type | INTR_INFO_VALID_MASK | errCodeValid);
> +

Why not do a 1:1 copy?

> +	vmcs_write32(VM_ENTRY_INSTRUCTION_LEN,
> +		vmx->nested.vm_exit_instruction_len);
> +	if (errCodeValid)
> +		vmcs_write32(VM_ENTRY_EXCEPTION_ERROR_CODE,
> +			vmx->nested.idt_vectoring_error_code);
> +}
> +
>   #ifdef CONFIG_X86_64
>   #define R "r"
>   #define Q "q"

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.