From: "Jan Beulich" <JBeulich@suse.com>
To: "David Vrabel" <david.vrabel@citrix.com>
Cc: <x86@kernel.org>, "Thomas Gleixner" <tglx@linutronix.de>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
<xen-devel@lists.xenproject.org>,
"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
"Ingo Molnar" <mingo@redhat.com>, <linux-kernel@vger.kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [Xen-devel] [PATCH 4/4] x86/xen: use the maximum MFN to calculate the required DMA mask
Date: Thu, 20 Nov 2014 12:21:23 +0100 [thread overview]
Message-ID: <546DDCC302000078000494C9@smtp.nue.novell.com> (raw)
In-Reply-To: <1416412921-23671-5-git-send-email-david.vrabel@citrix.com>
>>> On 19.11.14 at 17:02, <david.vrabel@citrix.com> wrote:
> On a Xen PV guest the DMA addresses and physical addresses are not 1:1
> (such as Xen PV guests) and the generic dma_get_required_mask() does
> not return the correct mask (since it uses max_pfn).
>
> Some device drivers (such as mptsas, mpt2sas) use
> dma_get_required_mask() to set the device's DMA mask to allow them to
> use only 32-bit DMA addresses in hardware structures. This results in
> unnecessary use of the SWIOTLB if DMA addresses are more than 32-bits,
> impacting performance significantly.
>
> Provide a get_required_mask op that uses the maximum MFN to calculate
> the DMA mask.
>
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
prev parent reply other threads:[~2014-11-20 11:41 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-19 16:01 [PATCHv3 0/4]: dma, x86, xen: reduce SWIOTLB usage in Xen guests David Vrabel
2014-11-19 16:01 ` [PATCH 1/4] dma: add dma_get_required_mask_from_max_pfn() David Vrabel
2014-11-19 16:01 ` [PATCH 2/4] ia64: use common dma_get_required_mask_from_pfn() David Vrabel
2014-11-19 17:33 ` Stefano Stabellini
2014-11-19 16:02 ` [PATCH 3/4] x86: allow dma_get_required_mask() to be overridden David Vrabel
2014-11-19 16:02 ` [PATCH 4/4] x86/xen: use the maximum MFN to calculate the required DMA mask David Vrabel
2014-11-19 17:51 ` [Xen-devel] " Stefano Stabellini
2014-11-20 11:42 ` David Vrabel
2014-11-20 11:21 ` Jan Beulich [this message]
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