From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756427AbaKSSC3 (ORCPT ); Wed, 19 Nov 2014 13:02:29 -0500 Received: from smtp02.citrix.com ([66.165.176.63]:33029 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755520AbaKSSC2 (ORCPT ); Wed, 19 Nov 2014 13:02:28 -0500 X-IronPort-AV: E=Sophos;i="5.07,418,1413244800"; d="scan'208";a="194487346" Date: Wed, 19 Nov 2014 17:51:02 +0000 From: Stefano Stabellini X-X-Sender: sstabellini@kaball.uk.xensource.com To: David Vrabel CC: , Greg Kroah-Hartman , , Ingo Molnar , "H. Peter Anvin" , , Thomas Gleixner , Boris Ostrovsky Subject: Re: [Xen-devel] [PATCH 4/4] x86/xen: use the maximum MFN to calculate the required DMA mask In-Reply-To: <1416412921-23671-5-git-send-email-david.vrabel@citrix.com> Message-ID: References: <1416412921-23671-1-git-send-email-david.vrabel@citrix.com> <1416412921-23671-5-git-send-email-david.vrabel@citrix.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" X-DLP: MIA1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 19 Nov 2014, David Vrabel 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 > --- > arch/x86/xen/pci-swiotlb-xen.c | 1 + > drivers/xen/swiotlb-xen.c | 13 +++++++++++++ > include/xen/swiotlb-xen.h | 4 ++++ > 3 files changed, 18 insertions(+) > > diff --git a/arch/x86/xen/pci-swiotlb-xen.c b/arch/x86/xen/pci-swiotlb-xen.c > index 0e98e5d..a5d180a 100644 > --- a/arch/x86/xen/pci-swiotlb-xen.c > +++ b/arch/x86/xen/pci-swiotlb-xen.c > @@ -31,6 +31,7 @@ static struct dma_map_ops xen_swiotlb_dma_ops = { > .map_page = xen_swiotlb_map_page, > .unmap_page = xen_swiotlb_unmap_page, > .dma_supported = xen_swiotlb_dma_supported, > + .get_required_mask = xen_swiotlb_get_required_mask, > }; > > /* > diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c > index ebd8f21..654587d 100644 > --- a/drivers/xen/swiotlb-xen.c > +++ b/drivers/xen/swiotlb-xen.c > @@ -42,9 +42,11 @@ > #include > #include > #include > +#include > > #include > #include > +#include > > #include > /* > @@ -683,3 +685,14 @@ xen_swiotlb_set_dma_mask(struct device *dev, u64 dma_mask) > return 0; > } > EXPORT_SYMBOL_GPL(xen_swiotlb_set_dma_mask); > + > +u64 > +xen_swiotlb_get_required_mask(struct device *dev) > +{ > + unsigned long max_mfn; > + > + max_mfn = HYPERVISOR_memory_op(XENMEM_maximum_ram_page, NULL); As Jan pointed out, I think you need to change the prototype of HYPERVISOR_memory_op to return long. Please do consistently across all relevant archs. > + return DMA_BIT_MASK(fls_long(max_mfn - 1) + PAGE_SHIFT); > +} > +EXPORT_SYMBOL_GPL(xen_swiotlb_get_required_mask); > diff --git a/include/xen/swiotlb-xen.h b/include/xen/swiotlb-xen.h > index 8b2eb93..6408888 100644 > --- a/include/xen/swiotlb-xen.h > +++ b/include/xen/swiotlb-xen.h > @@ -58,4 +58,8 @@ xen_swiotlb_dma_supported(struct device *hwdev, u64 mask); > > extern int > xen_swiotlb_set_dma_mask(struct device *dev, u64 dma_mask); > + > +extern u64 > +xen_swiotlb_get_required_mask(struct device *dev); > + > #endif /* __LINUX_SWIOTLB_XEN_H */ > -- > 1.7.10.4 > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > http://lists.xen.org/xen-devel >