Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756678AbaKTLvh (ORCPT ); Thu, 20 Nov 2014 06:51:37 -0500 Received: from smtp02.citrix.com ([66.165.176.63]:55564 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751894AbaKTLuf (ORCPT ); Thu, 20 Nov 2014 06:50:35 -0500 X-IronPort-AV: E=Sophos;i="5.07,423,1413244800"; d="scan'208";a="194755370" From: David Vrabel To: CC: David Vrabel , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , , , "Konrad Rzeszutek Wilk" , Boris Ostrovsky , Greg Kroah-Hartman Subject: [PATCH 4/4] x86/xen: assume a 64-bit DMA mask is required Date: Thu, 20 Nov 2014 11:50:25 +0000 Message-ID: <1416484225-28054-5-git-send-email-david.vrabel@citrix.com> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1416484225-28054-1-git-send-email-david.vrabel@citrix.com> References: <1416484225-28054-1-git-send-email-david.vrabel@citrix.com> MIME-Version: 1.0 Content-Type: text/plain X-DLP: MIA1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. We could base the DMA mask on the maximum MFN but: a) The hypercall op to get the maximum MFN (XENMEM_maximum_ram_page) will truncate the result to an int in 32-bit guests. b) Future uses of the IOMMU in Xen may map frames at bus addresses above the end of RAM. So, just assume a 64-bit DMA mask is always required. Signed-off-by: David Vrabel --- arch/x86/xen/pci-swiotlb-xen.c | 1 + drivers/xen/swiotlb-xen.c | 9 +++++++++ include/xen/swiotlb-xen.h | 4 ++++ 3 files changed, 14 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..767d048 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 +685,10 @@ 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) +{ + return DMA_BIT_MASK(64); +} +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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/