Re: [PATCH] iommu/vt-d: remove redundant variable no_platform_optin

[Zhenzhong Duan]

Hi Baolu,

On Thu, Nov 5, 2020 at 9:47 AM Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote:
>
> Hi Zhenzhong,
>
> On 11/4/20 4:19 PM, Zhenzhong Duan wrote:
> > no_platform_optin is redundant with dmar_disabled and it's only used in
> > platform_optin_force_iommu(), remove it and use dmar_disabled instead.
>
> It's actually not.
>
> If CONFIG_INTEL_IOMMU_DEFAULT_ON is not set, we will get "dmar_disable =
> 1" and "no_platform_optin = 0". In this case, we must force the iommu on
> and set dmar_disable = 0.
>
> The real use case: if a kernel built with [CONFIG_INTEL_IOMMU_DEFAULT_ON
> = n] running on a platform with thunderbolt ports, we must force IOMMU
> on so that the system could be protected from possible malicious
> peripherals.

Thanks for your explanation, clear now and sorry for the noise.

Regards
Zhenzhong