linux-kernel - [PATCH 1/2] [Patch-next -v2] ACPI, APEI Fix the return value(==NULL) of acpi_pre

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Message-ID: <4C6B1F63.9050703@np.css.fujitsu.com>
Date:	Wed, 18 Aug 2010 08:46:43 +0900
From:	Jin Dongming <jin.dongming@...css.fujitsu.com>
To:	Huang Ying <ying.huang@...el.com>
CC:	Randy Dunlap <randy.dunlap@...cle.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Andi Kleen <andi@...stfloor.org>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	LKLM <linux-kernel@...r.kernel.org>,
	ACPI <linux-acpi@...r.kernel.org>
Subject: [PATCH 1/2] [Patch-next -v2] ACPI, APEI Fix the return value(==NULL)
 of acpi_pre_map().

acpi_pre_map() is used for remapping the physical address of I/O, so
it should be return NULL or remapped virtual address. The problem is
that when (paddr - pg_off) equals 0, no matter whether I/O remapping is
successful or not, the function returns NULL.

In acpi_pre_map(), after the physical address is remapped sucessfully,
it will check whether the physical address has been added into acpi_iomaps
list again.
   - If the physical address has beed added into acpi_iomaps, the virtual
     address will be saved in vaddr.
   - Otherwise, NULL be saved in vaddr.

So if the physical address is the first time to be remapped, vaddr will be
NULL always.

In many cases, (paddr - pg_off) may not equal 0. So the function could work
well. In our machine, (paddr - pg_off) equals 0, so the return value of
acpi_pre_map() is NULL.

This patch fixed it and I confirmed it on x86_64 next-tree.

Signed-off-by: Jin Dongming <jin.dongming@...css.fujitsu.com>
---
 drivers/acpi/atomicio.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/atomicio.c b/drivers/acpi/atomicio.c
index 8f8bd73..1bc2614 100644
--- a/drivers/acpi/atomicio.c
+++ b/drivers/acpi/atomicio.c
@@ -133,7 +133,7 @@ static void __iomem *acpi_pre_map(phys_addr_t paddr,
 
 	spin_lock_irqsave(&acpi_iomaps_lock, flags);
 	vaddr = __acpi_try_ioremap(paddr, size);
-	if (vaddr) {
+	if (unlikely(vaddr)) {
 		spin_unlock_irqrestore(&acpi_iomaps_lock, flags);
 		iounmap(map->vaddr);
 		kfree(map);
@@ -142,7 +142,7 @@ static void __iomem *acpi_pre_map(phys_addr_t paddr,
 	list_add_tail_rcu(&map->list, &acpi_iomaps);
 	spin_unlock_irqrestore(&acpi_iomaps_lock, flags);
 
-	return vaddr + (paddr - pg_off);
+	return map->vaddr + (paddr - pg_off);
 err_unmap:
 	iounmap(vaddr);
 	return NULL;
-- 
1.7.1.1

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