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Date: Wed, 25 Feb 2026 16:47:46 -0600
From: Bjorn Helgaas <helgaas@kernel.org>
To: David Matlack <dmatlack@google.com>
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Subject: Re: [PATCH v2 03/22] PCI: Inherit bus numbers from previous kernel
 during Live Update
Message-ID: <20260225224746.GA3714478@bhelgaas>
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In-Reply-To: <20260129212510.967611-4-dmatlack@google.com>

On Thu, Jan 29, 2026 at 09:24:50PM +0000, David Matlack wrote:
> Inherit bus numbers from the previous kernel during a Live Update when
> one or more PCI devices are being preserved. This is necessary so that
> preserved devices can DMA through the IOMMU during a Live Update
> (changing bus numbers would break IOMMU translation).

I think changing bus numbers would break DMA regardless of whether an
IOMMU is involved.  Completions carrying the data for DMA reads are
routed back to the Requester ID of the read.