linux-kernel - Re: [PATCH v2] iommu/dma: Add config for PCI SAC address trick

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Message-ID: <653fba02-7eef-5f0d-66dd-7599af84db86@arm.com>
Date:   Thu, 23 Jun 2022 12:41:00 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     will@...nel.org, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, hch@....de, john.garry@...wei.com
Subject: Re: [PATCH v2] iommu/dma: Add config for PCI SAC address trick

On 2022-06-23 12:33, Joerg Roedel wrote:
> On Wed, Jun 22, 2022 at 02:12:39PM +0100, Robin Murphy wrote:
>> Thanks for your bravery!
> 
> It already starts, with that patch I am getting:
> 
> 	xhci_hcd 0000:02:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x000f address=0xff00ffffffefe000 flags=0x0000]
> 
> In my kernel log. The device is an AMD XHCI controller and seems to
> funciton normally after boot. The message disappears with
> iommu.forcedac=0.
> 
> Need to look more into that...

Given how amd_iommu_domain_alloc() sets the domain aperture, presumably 
the DMA address allocated was 0xffffffffffefe000? Odd that it gets bits 
punched out in the middle rather than simply truncated off the top as I 
would have expected :/

Robin.