linux-kernel - Re: [PATCH 2/6] iommu/vt-d: move up no_iommu and dmar

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Message-ID: <20140704090640.GS26537@8bytes.org>
Date:	Fri, 4 Jul 2014 11:06:40 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	Yijing Wang <wangyijing@...wei.com>
Cc:	David Woodhouse <dwmw2@...radead.org>,
	iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/6] iommu/vt-d: move up no_iommu and dmar_disabled check

On Tue, May 20, 2014 at 08:37:48PM +0800, Yijing Wang wrote:
> Move up the no_iommu and dmar_disabled check, avoid the
> useless initialization for dmar.
> 
> Signed-off-by: Yijing Wang <wangyijing@...wei.com>
> ---
>  drivers/iommu/intel-iommu.c |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index e020dcf..6b71608 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -3948,6 +3948,9 @@ int __init intel_iommu_init(void)
>  	/* VT-d is required for a TXT/tboot launch, so enforce that */
>  	force_on = tboot_force_iommu();
>  
> +	if (no_iommu || dmar_disabled)
> +		return ret;
> +
>  	if (iommu_init_mempool()) {
>  		if (force_on)
>  			panic("tboot: Failed to initialize iommu memory\n");
> @@ -3974,9 +3977,6 @@ int __init intel_iommu_init(void)
>  		goto out_free_dmar;
>  	}
>  
> -	if (no_iommu || dmar_disabled)
> -		goto out_free_dmar;
> -
>  	if (list_empty(&dmar_rmrr_units))
>  		printk(KERN_INFO "DMAR: No RMRR found\n");

This breaks the kexec case were the old kernel had VT-d enabled and the
new one disabled. In this case the new kernel might need to disable the
IOMMUs.


	Joerg


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