linux-kernel - [PATCH] x86, calgary: use 8M TCE table size by default

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Date:	Fri,  7 Mar 2014 16:10:16 +0800
From:	WANG Chao <chaowang@...hat.com>
To:	Muli Ben-Yehuda <muli@...technion.ac.il>,
	"Jon D. Mason" <jdmason@...zu.us>,
	"H. Peter Anvin" <hpa@...or.com>, Vivek Goyal <vgoyal@...hat.com>,
	Baoquan He <bhe@...hat.com>
Cc:	kexec@...ts.infradead.org, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] x86, calgary: use 8M TCE table size by default

kexec-tools wants to pass kdump kernel needed memmap via E820 directly,
instead of memmap=exactmap. That'll make saved_max_pfn totally useless.

Muli suggest to hard code TCE table size to max (8M) so that kdump
kernel could use this default size and kexec-tools doesn't need to pass
saved_max_pfn to kdump kernel in any way.

Signed-off-by: WANG Chao <chaowang@...hat.com>
---
 arch/x86/kernel/pci-calgary_64.c | 25 ++++++++-----------------
 1 file changed, 8 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kernel/pci-calgary_64.c b/arch/x86/kernel/pci-calgary_64.c
index 299d493..b26ab94 100644
--- a/arch/x86/kernel/pci-calgary_64.c
+++ b/arch/x86/kernel/pci-calgary_64.c
@@ -1207,25 +1207,17 @@ error:
 	return ret;
 }
 
-static inline int __init determine_tce_table_size(u64 ram)
+static inline int __init determine_tce_table_size(void)
 {
-	int ret;
-
 	if (specified_table_size != TCE_TABLE_SIZE_UNSPECIFIED)
 		return specified_table_size;
+	else
+		/*
+		 * Use 8M by default to get rid of saved_max_pfn,
+		 * suggested by Muli
+		 */
+		return TCE_TABLE_SIZE_8M;
 
-	/*
-	 * Table sizes are from 0 to 7 (TCE_TABLE_SIZE_64K to
-	 * TCE_TABLE_SIZE_8M). Table size 0 has 8K entries and each
-	 * larger table size has twice as many entries, so shift the
-	 * max ram address by 13 to divide by 8K and then look at the
-	 * order of the result to choose between 0-7.
-	 */
-	ret = get_order(ram >> 13);
-	if (ret > TCE_TABLE_SIZE_8M)
-		ret = TCE_TABLE_SIZE_8M;
-
-	return ret;
 }
 
 static int __init build_detail_arrays(void)
@@ -1418,8 +1410,7 @@ int __init detect_calgary(void)
 		return -ENOMEM;
 	}
 
-	specified_table_size = determine_tce_table_size((is_kdump_kernel() ?
-					saved_max_pfn : max_pfn) * PAGE_SIZE);
+	specified_table_size = determine_tce_table_size();
 
 	for (bus = 0; bus < MAX_PHB_BUS_NUM; bus++) {
 		struct calgary_bus_info *info = &bus_info[bus];
-- 
1.8.5.3

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