linux-kernel - [PATCH v8 18/19] swiotlb-xen: no need to do execute two bus_to

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Message-ID: <1382031814-8782-18-git-send-email-stefano.stabellini@eu.citrix.com>
Date:	Thu, 17 Oct 2013 18:43:33 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	<xen-devel@...ts.xensource.com>
CC:	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <konrad.wilk@...cle.com>,
	<Stefano.Stabellini@...citrix.com>, <Ian.Campbell@...rix.com>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>
Subject: [PATCH v8 18/19] swiotlb-xen: no need to do execute two bus_to_phys translations in a row

xen_unmap_single calls xen_bus_to_phys, then passes dev_addr to
is_xen_swiotlb_buffer that calls xen_bus_to_phys again.
xen_bus_to_phys is potentially a slow operation that might involve
walking a tree.
We can avoid calling xen_bus_to_phys twice by removing the
is_xen_swiotlb_buffer call and doing the check directly in
xen_unmap_single using the physical address.

Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
---
 drivers/xen/swiotlb-xen.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 4d50058..6d9ca61 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -426,8 +426,8 @@ static void xen_unmap_single(struct device *hwdev, dma_addr_t dev_addr,
 
 	xen_dma_unmap_page(hwdev, paddr, size, dir, attrs);
 
-	/* NOTE: We use dev_addr here, not paddr! */
-	if (is_xen_swiotlb_buffer(dev_addr)) {
+	if (paddr >= virt_to_phys(xen_io_tlb_start) &&
+		paddr < virt_to_phys(xen_io_tlb_end)) {
 		swiotlb_tbl_unmap_single(hwdev, paddr, size, dir);
 		return;
 	}
-- 
1.7.2.5

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