linux-kernel - Re: [PATCH 3/4] Intel pci: Limit dmar_init_reserved

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Message-ID: <4D94FC21.6040601@sgi.com>
Date:	Thu, 31 Mar 2011 15:11:45 -0700
From:	Mike Travis <travis@....com>
To:	David Woodhouse <dwmw2@...radead.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Chris Wright <chrisw@...s-sol.org>
Cc:	Mike Habeck <habeck@....com>, iommu@...ts.linux-foundation.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] Intel pci: Limit dmar_init_reserved_ranges

Chris - did you have any comment on this patch?

David/Jesse - should I resubmit the entire series for consideration?  We
have a number of customers that have encountered this problem.

Thanks,
Mike

Mike Travis wrote:
>     dmar_init_reserved_ranges() reserves the card's MMIO ranges to
>     prevent handing out a DMA map that would overlap with the MMIO range.
>     The problem while the Nvidia GPU has 64bit BARs, it's capable of
>     receiving > 40bit PIOs, but can't generate > 40bit DMAs.
> 
>     So when the iommu code reserves these MMIO ranges a > 40bit
>     entry ends up getting in the rbtree.  On a UV test system with
>     the Nvidia cards, the BARs are:
> 
>       0001:36:00.0 VGA compatible controller: nVidia Corporation GT200GL 
> 	  Region 0: Memory at 92000000 (32-bit, non-prefetchable) [size=16M]
> 	  Region 1: Memory at f8200000000 (64-bit, prefetchable) [size=256M]
> 	  Region 3: Memory at 90000000 (64-bit, non-prefetchable) [size=32M]
> 
>     So this 44bit MMIO address 0xf8200000000 ends up in the rbtree.  As DMA
>     maps get added and deleted from the rbtree we can end up getting a cached
>     entry to this 0xf8200000000 entry... this is what results in the code
>     handing out the invalid DMA map of 0xf81fffff000:
> 
> 	    [ 0xf8200000000-1 >> PAGE_SIZE << PAGE_SIZE ]
> 
>     The IOVA code needs to better honor the "limit_pfn" when allocating
>     these maps.
> 
> Signed-off-by: Mike Travis <travis@....com>
> Reviewed-by: Mike Habeck <habeck@....com>
> ---
>  drivers/pci/intel-iommu.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> --- linux.orig/drivers/pci/intel-iommu.c
> +++ linux/drivers/pci/intel-iommu.c
> @@ -1323,7 +1323,8 @@ static void dmar_init_reserved_ranges(vo
>  
>  		for (i = 0; i < PCI_NUM_RESOURCES; i++) {
>  			r = &pdev->resource[i];
> -			if (!r->flags || !(r->flags & IORESOURCE_MEM))
> +			if (!r->flags || !(r->flags & IORESOURCE_MEM) ||
> +			    r->start > pdev->dma_mask)
>  				continue;
>  			iova = reserve_iova(&reserved_iova_list,
>  					    IOVA_PFN(r->start),
> 
--
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