2010-08-17 23:46:55

by Jin Dongming

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 <[email protected]>
---
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

2010-08-18 04:17:10

by Huang, Ying

Subject: Re: [PATCH 1/2] [Patch-next -v2] ACPI, APEI Fix the return value(==NULL) of acpi_pre_map().

On Wed, 2010-08-18 at 07:46 +0800, Jin Dongming wrote:
> 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 <[email protected]>
Acked-by: Huang Ying <[email protected]>

Best Regards,
Huang Ying