linux-kernel - Re: [PATCH 2/2] iommu/vt-d: Fix checks in pgtable

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Message-ID: <f6d109cd-9a7e-416f-87d7-429e584e3b3e@linux.intel.com>
Date: Wed, 23 Oct 2024 15:41:37 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: "Duan, Zhenzhong" <zhenzhong.duan@...el.com>,
 "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc: baolu.lu@...ux.intel.com, "dwmw2@...radead.org" <dwmw2@...radead.org>,
 "joro@...tes.org" <joro@...tes.org>, "will@...nel.org" <will@...nel.org>,
 "robin.murphy@....com" <robin.murphy@....com>,
 "Peng, Chao P" <chao.p.peng@...el.com>,
 Kyung Min Park <kyung.min.park@...el.com>
Subject: Re: [PATCH 2/2] iommu/vt-d: Fix checks in pgtable_walk()

On 2024/10/23 13:16, Duan, Zhenzhong wrote:
>> -----Original Message-----
>> From: Baolu Lu<baolu.lu@...ux.intel.com>
>> Sent: Wednesday, October 23, 2024 12:50 PM
>> Subject: Re: [PATCH 2/2] iommu/vt-d: Fix checks in pgtable_walk()
>>
>> On 2024/10/22 17:50, Zhenzhong Duan wrote:
>>> It's not accurate to dump super page as non-present page,
>>> meanwhile bit7 in first level page table entry is PAT bit,
>> Can you please explain how the 'bit7 in first level page table entry' is
>> relevant to the changes made in this patch?
> When iterate to level 1, it is leaf page table entry, bit 7 is PAT bit instead of PS bit.
> dma_pte_superpage(pte) may return true, then " PTE not present at level 1" may
> be printed out.

I see. Thank you!

If you have a new version, can you please make it a bit clearer? My
understanding is that dma_pte_superpage(pte) should not check against
the leaf page table entries, right?

Thanks,
baolu