From: Zhenzhong Duan <zhenzhong.duan@gmail.com>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
iommu@lists.linux-foundation.org
Subject: Re: [PATCH] iommu/vt-d: remove redundant variable no_platform_optin
Date: Thu, 5 Nov 2020 10:19:36 +0800 [thread overview]
Message-ID: <CAFH1YnO4xas=YnUSYR3MjxRkFPvezHe7Rt4cdgZU4knvvQqzEA@mail.gmail.com> (raw)
In-Reply-To: <67fd98a2-23a9-b69a-4d60-a0698e243a85@linux.intel.com>
Hi Baolu,
On Thu, Nov 5, 2020 at 9:47 AM Lu Baolu <baolu.lu@linux.intel.com> 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
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prev parent reply other threads:[~2020-11-05 2:20 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-04 8:19 [PATCH] iommu/vt-d: remove redundant variable no_platform_optin Zhenzhong Duan
2020-11-05 1:40 ` Lu Baolu
2020-11-05 2:19 ` Zhenzhong Duan [this message]
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