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 whether I/O remapping is successful or not, the function returns
NULL always.
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 has never been remapped, the return value of
acpi_pre_map will be NULL always.
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
On Tue, 2010-08-17 at 08:56 +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 whether I/O remapping is successful or not, the function returns
> NULL always.
No. NULL is returned for error path only. Please check the code again.
> 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 has never been remapped, the return value of
> acpi_pre_map will be NULL always.
>
> 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)) {
pre_map is not performance critical, so "unlikely" here helps little.
> 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;
When will vaddr != map->vaddr?
Best Regards,
Huang Ying
(2010/08/17 10:37), Huang Ying wrote:
> On Tue, 2010-08-17 at 08:56 +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 whether I/O remapping is successful or not, the function returns
>> NULL always.
>
> No. NULL is returned for error path only. Please check the code again.
There three places used the local variable vaddr in acpi_pre_map() in next-tree.
1. 115 vaddr = __acpi_try_ioremap(paddr, size);
2. 122 vaddr = ioremap(pg_off, pg_sz);
3. 135 vaddr = __acpi_try_ioremap(paddr, size);
Let's think about the following statement.
Assumption: the physical address has never been remapped.
Step:
1. vaddr == NULL
Because the physical address is not registered in the acpi_iomaps,
it should be returned NULL from __acpi_try_ioremap().
2. vaddr == the virtual address of the physical address.
Here if ioremap is successful, the value of vaddr should be
the virtual address returned from ioremap().
3. vaddr == NULL <== IMPORTANT
Here it is because the physical address has not been registered
in the acpi_iomaps yet, it still return NULL from __acpi_try_ioremap().
So it is why vaddr == NULL, even if the physical address has never
been remapped.
Result: vaddr == NULL.
And if the vaddr is not NULL, it could not be added into acpi_iomaps.
Codes in acpi_pre_map() is like following.
134 spin_lock_irqsave(&acpi_iomaps_lock, flags);
135 vaddr = __acpi_try_ioremap(paddr, size); <== the 3rd step
136 if (vaddr) {
137 spin_unlock_irqrestore(&acpi_iomaps_lock, flags);
138 iounmap(map->vaddr);
139 kfree(map);
140 return vaddr;
141 }
142 list_add_tail_rcu(&map->list, &acpi_iomaps); <== add into acpi_iomaps.
143 spin_unlock_irqrestore(&acpi_iomaps_lock, flags);
>
>> 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 has never been remapped, the return value of
>> acpi_pre_map will be NULL always.
>>
>> 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)) {
>
> pre_map is not performance critical, so "unlikely" here helps little.
>
>> 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;
>
> When will vaddr != map->vaddr?
>
> Best Regards,
> Huang Ying
>
>
>
>
On Tue, 2010-08-17 at 10:43 +0800, Jin Dongming wrote:
> (2010/08/17 10:37), Huang Ying wrote:
> > On Tue, 2010-08-17 at 08:56 +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 whether I/O remapping is successful or not, the function returns
> >> NULL always.
> >
> > No. NULL is returned for error path only. Please check the code again.
>
> There three places used the local variable vaddr in acpi_pre_map() in next-tree.
> 1. 115 vaddr = __acpi_try_ioremap(paddr, size);
> 2. 122 vaddr = ioremap(pg_off, pg_sz);
> 3. 135 vaddr = __acpi_try_ioremap(paddr, size);
>
> Let's think about the following statement.
> Assumption: the physical address has never been remapped.
> Step:
> 1. vaddr == NULL
> Because the physical address is not registered in the acpi_iomaps,
> it should be returned NULL from __acpi_try_ioremap().
>
> 2. vaddr == the virtual address of the physical address.
> Here if ioremap is successful, the value of vaddr should be
> the virtual address returned from ioremap().
>
> 3. vaddr == NULL <== IMPORTANT
> Here it is because the physical address has not been registered
> in the acpi_iomaps yet, it still return NULL from __acpi_try_ioremap().
> So it is why vaddr == NULL, even if the physical address has never
> been remapped.
>
> Result: vaddr == NULL.
return vaddr + (paddr - pg_off), is not NULL for common cases.
> And if the vaddr is not NULL, it could not be added into acpi_iomaps.
> Codes in acpi_pre_map() is like following.
>
> 134 spin_lock_irqsave(&acpi_iomaps_lock, flags);
> 135 vaddr = __acpi_try_ioremap(paddr, size); <== the 3rd step
> 136 if (vaddr) {
> 137 spin_unlock_irqrestore(&acpi_iomaps_lock, flags);
> 138 iounmap(map->vaddr);
> 139 kfree(map);
> 140 return vaddr;
> 141 }
> 142 list_add_tail_rcu(&map->list, &acpi_iomaps); <== add into acpi_iomaps.
> 143 spin_unlock_irqrestore(&acpi_iomaps_lock, flags);
Oops, this is a bug, and your patch really fix it. But I think you
should change the patch description. NULL is not returned in almost all
cases. Because (paddr - pg_off) is not zero in common cases.
Best Regards,
Huang Ying
(2010/08/17 13:15), Huang Ying wrote:
> On Tue, 2010-08-17 at 10:43 +0800, Jin Dongming wrote:
>> (2010/08/17 10:37), Huang Ying wrote:
>>> On Tue, 2010-08-17 at 08:56 +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 whether I/O remapping is successful or not, the function returns
>>>> NULL always.
>>>
>>> No. NULL is returned for error path only. Please check the code again.
>>
>> There three places used the local variable vaddr in acpi_pre_map() in next-tree.
>> 1. 115 vaddr = __acpi_try_ioremap(paddr, size);
>> 2. 122 vaddr = ioremap(pg_off, pg_sz);
>> 3. 135 vaddr = __acpi_try_ioremap(paddr, size);
>>
>> Let's think about the following statement.
>> Assumption: the physical address has never been remapped.
>> Step:
>> 1. vaddr == NULL
>> Because the physical address is not registered in the acpi_iomaps,
>> it should be returned NULL from __acpi_try_ioremap().
>>
>> 2. vaddr == the virtual address of the physical address.
>> Here if ioremap is successful, the value of vaddr should be
>> the virtual address returned from ioremap().
>>
>> 3. vaddr == NULL <== IMPORTANT
>> Here it is because the physical address has not been registered
>> in the acpi_iomaps yet, it still return NULL from __acpi_try_ioremap().
>> So it is why vaddr == NULL, even if the physical address has never
>> been remapped.
>>
>> Result: vaddr == NULL.
>
> return vaddr + (paddr - pg_off), is not NULL for common cases.
>
>> And if the vaddr is not NULL, it could not be added into acpi_iomaps.
>> Codes in acpi_pre_map() is like following.
>>
>> 134 spin_lock_irqsave(&acpi_iomaps_lock, flags);
>> 135 vaddr = __acpi_try_ioremap(paddr, size); <== the 3rd step
>> 136 if (vaddr) {
>> 137 spin_unlock_irqrestore(&acpi_iomaps_lock, flags);
>> 138 iounmap(map->vaddr);
>> 139 kfree(map);
>> 140 return vaddr;
>> 141 }
>> 142 list_add_tail_rcu(&map->list, &acpi_iomaps); <== add into acpi_iomaps.
>> 143 spin_unlock_irqrestore(&acpi_iomaps_lock, flags);
>
> Oops, this is a bug, and your patch really fix it. But I think you
> should change the patch description. NULL is not returned in almost all
> cases. Because (paddr - pg_off) is not zero in common cases.
>
> Best Regards,
> Huang Ying
>
OK. I will modify the description of this patch and resend it.
Best Regards,
Jin Dongming
>
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