From: Vasant Hegde <vasant.hegde@amd.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Pranjal Shrivastava <praan@google.com>,
iommu@lists.linux.dev, linux-pci@vger.kernel.org,
linux-kernel@vger.kernel.org, Joerg Roedel <joro@8bytes.org>,
Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
Ankit Soni <ankit.soni@amd.com>,
Bjorn Helgaas <bhelgaas@google.com>,
Samiullah Khawaja <skhawaja@google.com>,
sashiko-bot@kernel.org
Subject: Re: [PATCH v3 2/5] iommu/amd: Fix DTE clearing and rename iommu_ignore_device()
Date: Fri, 4 Sep 2026 15:43:01 +0530 [thread overview]
Message-ID: <399db967-050d-48dc-afb5-5c77ee9cce65@amd.com> (raw)
In-Reply-To: <20260828115331.GC3922654@nvidia.com>
Jason,
On 8/28/2026 5:23 PM, Jason Gunthorpe wrote:
> On Fri, Aug 28, 2026 at 10:46:48AM +0530, Vasant Hegde wrote:
>>> Having the driver boot up with all DTEs programmed to identity (eg
>>> 0'd) and then try to fix them to blocking after the iommu probes
>>> devices is security backwards.
>>
>> During boot, it only sets dte.v bit.
>
> First it clears it to fully 0, what does 0 do in HW?
IF DTE is fully zero, then all requests are blocked for that devid.
>
> It doesn't make sense that you'd pass over the DTEs after
> probing if the original 0'd DTE was actually blocking?
During boot, it sets certain default values includ dte.v. It doesn't clear
everything. In probe path, if probe fails then its clearing it entirely.
May be we should just remove ignore_device() completely? as
- normal boot, its not yet configured, so no DMA is allowed
- kdump boot, old DTE is still valid and let it continue?
-Vasant
next prev parent reply other threads:[~2026-09-04 10:13 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-24 12:23 [PATCH v3 0/5] iommu/amd: Refactors for ATS robustness Pranjal Shrivastava
2026-08-24 12:23 ` [PATCH v3 1/5] iommu/amd: Refactor device probe and capability initialization Pranjal Shrivastava
2026-08-24 18:13 ` Jason Gunthorpe
2026-08-25 10:24 ` Pranjal Shrivastava
2026-08-25 11:50 ` Jason Gunthorpe
2026-08-25 6:59 ` Vasant Hegde
2026-08-25 10:25 ` Pranjal Shrivastava
2026-08-24 12:23 ` [PATCH v3 2/5] iommu/amd: Fix DTE clearing and rename iommu_ignore_device() Pranjal Shrivastava
2026-08-24 18:13 ` Jason Gunthorpe
2026-08-25 10:32 ` Pranjal Shrivastava
2026-08-25 11:49 ` Jason Gunthorpe
2026-08-25 17:29 ` Pranjal Shrivastava
2026-08-25 17:53 ` Jason Gunthorpe
2026-08-25 19:08 ` Pranjal Shrivastava
2026-08-26 11:28 ` Vasant Hegde
2026-08-26 12:21 ` Jason Gunthorpe
2026-08-28 5:16 ` Vasant Hegde
2026-08-28 11:53 ` Jason Gunthorpe
2026-09-04 10:13 ` Vasant Hegde [this message]
2026-09-04 14:25 ` Jason Gunthorpe
2026-08-24 21:47 ` Samiullah Khawaja
2026-08-25 7:01 ` Vasant Hegde
2026-08-24 12:23 ` [PATCH v3 3/5] iommu/amd: Split probe error paths to preserve IRQ remapping Pranjal Shrivastava
2026-08-24 18:13 ` Jason Gunthorpe
2026-08-25 10:34 ` Pranjal Shrivastava
2026-08-24 12:23 ` [PATCH v3 4/5] iommu/amd: Fail probe on ATS configuration failure Pranjal Shrivastava
2026-08-24 18:13 ` Jason Gunthorpe
2026-08-24 21:46 ` Samiullah Khawaja
2026-08-24 12:23 ` [PATCH v3 5/5] PCI/ATS: Mandate checking pci_ats_supported() before pci_prepare_ats() Pranjal Shrivastava
2026-08-24 18:13 ` Jason Gunthorpe
2026-08-24 18:13 ` [PATCH v3 0/5] iommu/amd: Refactors for ATS robustness Jason Gunthorpe
2026-08-25 10:39 ` Pranjal Shrivastava
2026-08-25 11:51 ` Jason Gunthorpe
2026-08-25 7:06 ` Vasant Hegde
2026-08-25 10:37 ` Pranjal Shrivastava
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