linux-kernel - Re: [PATCH 2/2] iommu: Use the user PGD for SVA if PTI is enabled

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Message-ID: <3aa28716-9d91-321a-0e52-58ae425ac598@linux.intel.com>
Date:   Wed, 31 Aug 2022 08:57:05 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>, iommu@...ts.linux.dev,
        x86@...nel.org, Joerg Roedel <joro@...tes.org>
Cc:     baolu.lu@...ux.intel.com, Raj Ashok <ashok.raj@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...el.com>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
        "Tian, Kevin" <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>
Subject: Re: [PATCH 2/2] iommu: Use the user PGD for SVA if PTI is enabled

On 8/23/22 4:12 AM, Jacob Pan wrote:
> With page table isolation, the kernel manages two sets of page tables
> for each process: one for user one for kernel. When enabling SVA, the
> current x86 IOMMU drivers bind device and PASID with the kernel copy
> of the process page table.
> 
> While there is no known "Meltdown" type of DMA attack, exposing
> kernel mapping to DMA intended for userspace makes the system vulnerable
> unnecessarily. It also breaks the intention of PTI.
> 
> This patch replaces kernel page table PGD with the user counterpart,
> thus fulfill the promise of PTI on the DMA side.
> 
> Signed-off-by: Jacob Pan<jacob.jun.pan@...ux.intel.com>

Reviewed-by: Lu Baolu <baolu.lu@...ux.intel.com>

Best regards,
baolu