On Wed, Feb 20, 2013 at 4:46 AM, Zhang, Yang Z <yang.z.zhang@xxxxxxxxx> wrote:
>>>
>>> +static void vmx_handle_external_intr(struct kvm_vcpu *vcpu) +{ +
>>> u32 exit_intr_info = vmcs_read32(VM_EXIT_INTR_INFO); + + /* +
>>> * If external interrupt exists, IF bit is set in rflags/eflags on
>>> the + * interrupt stack frame, and interrupt will be enabled on
>>> a return + * from interrupt handler. + */ + if
>>> ((exit_intr_info & (INTR_INFO_VALID_MASK | INTR_INFO_INTR_TYPE_MASK)) +
>>> == (INTR_INFO_VALID_MASK | INTR_TYPE_EXT_INTR)) {
>>> + unsigned int vector; + unsigned long
>>> entry; + gate_desc *desc; + struct vcpu_vmx
>>> *vmx = to_vmx(vcpu); + + vector = exit_intr_info &
>>> INTR_INFO_VECTOR_MASK; +#ifdef CONFIG_X86_64 + desc =
>>> (void *)vmx->host_idt_base + vector * 16; +#else + desc =
>>> (void *)vmx->host_idt_base + vector * 8; +#endif + +
>>> entry = gate_offset(*desc); + asm( +
>>> "mov %0, %%" _ASM_DX " \n\t" +#ifdef CONFIG_X86_64 +
>>> "mov %%" _ASM_SP ", %%" _ASM_BX " \n\t" +
>>> "and $0xfffffffffffffff0, %%" _ASM_SP " \n\t" +
>>> "mov %%ss, %%" _ASM_AX " \n\t" + "push %%"
>>> _ASM_AX " \n\t" + "push %%" _ASM_BX " \n\t"
>>> +#endif
>>
>> Are we sure no interrupts are using the IST feature? I guess it's unlikely.
> Linux uses IST for NMI, stack fault, machine-check, double fault and debug interrupt . No external interrupt will use it.
> This feature is only for external interrupt. So we don't need to check it here.
Ok, thanks for checking.
>
>>
>>> + "pushf \n\t"
>>> + "pop %%" _ASM_AX " \n\t"
>>> + "or $0x200, %%" _ASM_AX " \n\t"
>>> + "push %%" _ASM_AX " \n\t"
>>
>> Can simplify to pushf; orl $0x200, %%rsp.
> Sure.
>
>>> + "mov %%cs, %%" _ASM_AX " \n\t"
>>> + "push %%" _ASM_AX " \n\t"
>>
>> push %%cs
> "push %%cs" is invalid in x86_64.
Oops. 'push[lq] $__KERNEL_CS' then.
>
>>> + "push intr_return \n\t"
>>
>> push $1f. Or even combine with the next instruction, and call %rdx.
> Which is faster? jmp or call?
Actually it doesn't matter, the processor is clever enough to minimize
the difference. But the code is simpler and shorter with 'call'.
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