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| Started by | "Williams, Dan J" <dan.j.williams@intel.com> |
|---|---|
| First post | 2015-11-01 21:30 +0100 |
| Last post | 2015-11-01 22:00 +0100 |
| Articles | 3 — 3 participants |
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[GIT PULL] memremap fix for 4.3 (v2) "Williams, Dan J" <dan.j.williams@intel.com> - 2015-11-01 21:30 +0100
Re: [GIT PULL] memremap fix for 4.3 (v2) Russell King - ARM Linux <linux@arm.linux.org.uk> - 2015-11-01 21:40 +0100
Re: [GIT PULL] memremap fix for 4.3 (v2) Dan Williams <dan.j.williams@intel.com> - 2015-11-01 22:00 +0100
| From | "Williams, Dan J" <dan.j.williams@intel.com> |
|---|---|
| Date | 2015-11-01 21:30 +0100 |
| Subject | [GIT PULL] memremap fix for 4.3 (v2) |
| Message-ID | <qq7qh-4uL-1@gated-at.bofh.it> |
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| From | Russell King - ARM Linux <linux@arm.linux.org.uk> |
|---|---|
| Date | 2015-11-01 21:40 +0100 |
| Message-ID | <qq7zX-4y5-7@gated-at.bofh.it> |
| In reply to | #1260229 |
On Sun, Nov 01, 2015 at 08:24:25PM +0000, Williams, Dan J wrote:
> diff --git a/kernel/memremap.c b/kernel/memremap.c
> index 72b0c66628b6..9d6b55587eaa 100644
> --- a/kernel/memremap.c
> +++ b/kernel/memremap.c
> @@ -24,6 +24,16 @@ __weak void __iomem *ioremap_cache(resource_size_t offset, unsigned long size)
> }
> #endif
>
> +static void *try_ram_remap(resource_size_t offset, size_t size)
> +{
> + struct page *page = pfn_to_page(offset >> PAGE_SHIFT);
> +
> + /* In the simple case just return the existing linear address */
> + if (!PageHighMem(page))
> + return __va(offset);
> + return NULL; /* fallback to ioremap_cache */
Right, so a highmem page results in this returning NULL, which will...
> @@ -66,8 +76,8 @@ void *memremap(resource_size_t offset, size_t size, unsigned long flags)
> * the requested range is potentially in "System RAM"
> */
> if (is_ram == REGION_INTERSECTS)
> - addr = __va(offset);
> - else
> + addr = try_ram_remap(offset, size);
> + if (!addr)
> addr = ioremap_cache(offset, size);
cause ioremap_cache() to be called. That falls through on ARM to:
__arm_ioremap_pfn_caller()
and we will hit this (as I've mentioned before through explanation
rather than quoting code):
/*
* Don't allow RAM to be mapped - this causes problems with ARMv6+
*/
if (WARN_ON(pfn_valid(pfn)))
return NULL;
--
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
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| From | Dan Williams <dan.j.williams@intel.com> |
|---|---|
| Date | 2015-11-01 22:00 +0100 |
| Message-ID | <qq7Tj-4F2-9@gated-at.bofh.it> |
| In reply to | #1260233 |
On Sun, Nov 1, 2015 at 12:36 PM, Russell King - ARM Linux
<linux@arm.linux.org.uk> wrote:
> On Sun, Nov 01, 2015 at 08:24:25PM +0000, Williams, Dan J wrote:
>> diff --git a/kernel/memremap.c b/kernel/memremap.c
>> index 72b0c66628b6..9d6b55587eaa 100644
>> --- a/kernel/memremap.c
>> +++ b/kernel/memremap.c
>> @@ -24,6 +24,16 @@ __weak void __iomem *ioremap_cache(resource_size_t offset, unsigned long size)
>> }
>> #endif
>>
>> +static void *try_ram_remap(resource_size_t offset, size_t size)
>> +{
>> + struct page *page = pfn_to_page(offset >> PAGE_SHIFT);
>> +
>> + /* In the simple case just return the existing linear address */
>> + if (!PageHighMem(page))
>> + return __va(offset);
>> + return NULL; /* fallback to ioremap_cache */
>
> Right, so a highmem page results in this returning NULL, which will...
>
>> @@ -66,8 +76,8 @@ void *memremap(resource_size_t offset, size_t size, unsigned long flags)
>> * the requested range is potentially in "System RAM"
>> */
>> if (is_ram == REGION_INTERSECTS)
>> - addr = __va(offset);
>> - else
>> + addr = try_ram_remap(offset, size);
>> + if (!addr)
>> addr = ioremap_cache(offset, size);
>
> cause ioremap_cache() to be called. That falls through on ARM to:
>
> __arm_ioremap_pfn_caller()
>
> and we will hit this (as I've mentioned before through explanation
> rather than quoting code):
>
> /*
> * Don't allow RAM to be mapped - this causes problems with ARMv6+
> */
> if (WARN_ON(pfn_valid(pfn)))
> return NULL;
>
Right, which means the caller is broken and shouldn't be using
memremap, same as misuse of ioremap_cache today.
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