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From: David Vrabel <david.vrabel@citrix.com>
To: Stefano Panella <stefano.panella@citrix.com>
Cc: <linux-kernel@vger.kernel.org>, <konrad.wilk@oracle.com>,
	<xen-devel@lists.xensource.com>
Subject: Re: [Xen-devel] [PATCH 1/1] XEN: Use correct masking in	xen_swiotlb_alloc_coherent.
Date: Fri, 31 Aug 2012 13:47:05 +0100	[thread overview]
Message-ID: <5040B249.4000306@citrix.com> (raw)
In-Reply-To: <1346407072-6405-1-git-send-email-stefano.panella@citrix.com>

On 31/08/12 10:57, Stefano Panella wrote:
> When running 32-bit pvops-dom0 and a driver tries to allocate a coherent
> DMA-memory the xen swiotlb-implementation returned memory beyond 4GB.
> 
> This caused for example not working sound on a system with 4 GB and a 64-bit
> compatible sound-card with sets the DMA-mask to 64bit.
> 
> On bare-metal and the forward-ported xen-dom0 patches from OpenSuse a coherent
> DMA-memory is always allocated inside the 32-bit address-range by calling
> dma_alloc_coherent_mask.

We should have the same behaviour under Xen as bare metal so:

Acked-By: David Vrabel <david.vrabel@citrix.com>

This does limit the DMA mask to 32-bits by passing it through an
unsigned long, which seems a bit sneaky...

Presumably the sound card is capable of handling 64 bit physical
addresses (or it would break under 64-bit kernels) so it's not clear why
this sound driver requires this restriction.

Is there a bug in the sound driver or sound subsystem where it's
truncating a dma_addr_t by assigning it to an unsigned long or similar?

> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -232,7 +232,7 @@ xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
>  		return ret;
>  
>  	if (hwdev && hwdev->coherent_dma_mask)
> -		dma_mask = hwdev->coherent_dma_mask;
> +		dma_mask = dma_alloc_coherent_mask(hwdev, flags);

Suggest

    if (hwdev)
        dma_mask = dma_alloc_coherent_mask(hwdev, flags)

>  	phys = virt_to_phys(ret);
>  	dev_addr = xen_phys_to_bus(phys);

David

  reply	other threads:[~2012-08-31 12:47 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-08-31  9:57 Stefano Panella
2012-08-31 12:47 ` David Vrabel [this message]
2012-08-31 16:40   ` [Xen-devel] " Konrad Rzeszutek Wilk
2012-09-04 14:07     ` Stefano Panella
2012-09-04 14:37       ` Konrad Rzeszutek Wilk
2012-09-04 14:55         ` David Vrabel
2012-09-04 15:12           ` Stefano Panella
2012-09-04 16:44             ` David Vrabel
2012-09-04 16:40               ` Konrad Rzeszutek Wilk
2012-09-05 13:13                 ` Stefano Panella
2012-09-05 14:33       ` Konrad Rzeszutek Wilk

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