linux-kernel - Re: [lkp] [iommu/vt] 571dbbd4d04: DMAR-IR: Failed to copy IR table for dmar1 from previous kernel

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Date:	Thu, 2 Jul 2015 08:39:25 +0200
From:	Joerg Roedel <jroedel@...e.de>
To:	Huang Ying <ying.huang@...el.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, LKP ML <lkp@...org>
Subject: Re: [lkp] [iommu/vt] 571dbbd4d04: DMAR-IR: Failed to copy IR table
 for dmar1 from previous kernel

On Thu, Jul 02, 2015 at 01:14:18PM +0800, Huang Ying wrote:
> FYI, we noticed the below changes on
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> commit 571dbbd4d044e11c78bc077acb3ccef4c77b096e ("iommu/vt-d: Don't disable IR when it was previously enabled")
> 
> The following new message in kernel log may make end user confusing.
> 
> [    0.503764] DMAR-IR: IRQ remapping was enabled on dmar0 but we are not in kdump mode
> [    0.512418] DMAR-IR: Failed to copy IR table for dmar0 from previous kernel
> [    0.520501] DMAR-IR: IRQ remapping was enabled on dmar1 but we are not in kdump mode
> [    0.529154] DMAR-IR: Failed to copy IR table for dmar1 from previous kernel
> [    0.537077] DMAR-IR: Enabled IRQ remapping in x2apic mode

This is not a problem, the kernel detected that the IOMMU was already
enabled, but it is not booting into a kdump kernel so it is not trying
to copy over translation tables. The messages for this case are indeed a
bit misleading, it looks like the kernel tried to copy the translation
tables, but it didn't. I'll fix this.

What were you doing to trigger this, it is quite uncommon to find the
IOMMU enabled on a normal kernel boot. Did you boot with kexec into a
new kernel?


	Joerg

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