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Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel…
…/git/x86/linux-2.6-x86
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/x86/linux-2.6-x86: (613 commits)
x86: standalone trampoline code
x86: move suspend wakeup code to C
x86: coding style fixes to arch/x86/kernel/acpi/sleep.c
x86: setup_trampoline() - fix section mismatch warning
x86: section mismatch fixes, #1
x86: fix paranoia about using BIOS quickboot mechanism.
x86: print out buggy mptable
x86: use cpu_online()
x86: use cpumask_of_cpu()
x86: remove unnecessary tmp local variable
x86: remove unnecessary memset()
x86: use ioapic_read_entry() and ioapic_write_entry()
x86: avoid redundant loop in io_apic_level_ack_pending()
x86: remove superfluous initialisation in boot code.
x86: merge mpparse_{32,64}.c
x86: unify mp_register_gsi
x86: unify mp_config_acpi_legacy_irqs
x86: unify mp_register_ioapic
x86: unify uniq_io_apic_id
x86: unify smp_scan_config
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,100 @@ | ||
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| PAT (Page Attribute Table) | ||
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| x86 Page Attribute Table (PAT) allows for setting the memory attribute at the | ||
| page level granularity. PAT is complementary to the MTRR settings which allows | ||
| for setting of memory types over physical address ranges. However, PAT is | ||
| more flexible than MTRR due to its capability to set attributes at page level | ||
| and also due to the fact that there are no hardware limitations on number of | ||
| such attribute settings allowed. Added flexibility comes with guidelines for | ||
| not having memory type aliasing for the same physical memory with multiple | ||
| virtual addresses. | ||
|
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| PAT allows for different types of memory attributes. The most commonly used | ||
| ones that will be supported at this time are Write-back, Uncached, | ||
| Write-combined and Uncached Minus. | ||
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| There are many different APIs in the kernel that allows setting of memory | ||
| attributes at the page level. In order to avoid aliasing, these interfaces | ||
| should be used thoughtfully. Below is a table of interfaces available, | ||
| their intended usage and their memory attribute relationships. Internally, | ||
| these APIs use a reserve_memtype()/free_memtype() interface on the physical | ||
| address range to avoid any aliasing. | ||
|
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||
|
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| ------------------------------------------------------------------- | ||
| API | RAM | ACPI,... | Reserved/Holes | | ||
| -----------------------|----------|------------|------------------| | ||
| | | | | | ||
| ioremap | -- | UC | UC | | ||
| | | | | | ||
| ioremap_cache | -- | WB | WB | | ||
| | | | | | ||
| ioremap_nocache | -- | UC | UC | | ||
| | | | | | ||
| ioremap_wc | -- | -- | WC | | ||
| | | | | | ||
| set_memory_uc | UC | -- | -- | | ||
| set_memory_wb | | | | | ||
| | | | | | ||
| set_memory_wc | WC | -- | -- | | ||
| set_memory_wb | | | | | ||
| | | | | | ||
| pci sysfs resource | -- | -- | UC | | ||
| | | | | | ||
| pci sysfs resource_wc | -- | -- | WC | | ||
| is IORESOURCE_PREFETCH| | | | | ||
| | | | | | ||
| pci proc | -- | -- | UC | | ||
| !PCIIOC_WRITE_COMBINE | | | | | ||
| | | | | | ||
| pci proc | -- | -- | WC | | ||
| PCIIOC_WRITE_COMBINE | | | | | ||
| | | | | | ||
| /dev/mem | -- | UC | UC | | ||
| read-write | | | | | ||
| | | | | | ||
| /dev/mem | -- | UC | UC | | ||
| mmap SYNC flag | | | | | ||
| | | | | | ||
| /dev/mem | -- | WB/WC/UC | WB/WC/UC | | ||
| mmap !SYNC flag | |(from exist-| (from exist- | | ||
| and | | ing alias)| ing alias) | | ||
| any alias to this area| | | | | ||
| | | | | | ||
| /dev/mem | -- | WB | WB | | ||
| mmap !SYNC flag | | | | | ||
| no alias to this area | | | | | ||
| and | | | | | ||
| MTRR says WB | | | | | ||
| | | | | | ||
| /dev/mem | -- | -- | UC_MINUS | | ||
| mmap !SYNC flag | | | | | ||
| no alias to this area | | | | | ||
| and | | | | | ||
| MTRR says !WB | | | | | ||
| | | | | | ||
| ------------------------------------------------------------------- | ||
|
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||
| Notes: | ||
|
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| -- in the above table mean "Not suggested usage for the API". Some of the --'s | ||
| are strictly enforced by the kernel. Some others are not really enforced | ||
| today, but may be enforced in future. | ||
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| For ioremap and pci access through /sys or /proc - The actual type returned | ||
| can be more restrictive, in case of any existing aliasing for that address. | ||
| For example: If there is an existing uncached mapping, a new ioremap_wc can | ||
| return uncached mapping in place of write-combine requested. | ||
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| set_memory_[uc|wc] and set_memory_wb should be used in pairs, where driver will | ||
| first make a region uc or wc and switch it back to wb after use. | ||
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| Over time writes to /proc/mtrr will be deprecated in favor of using PAT based | ||
| interfaces. Users writing to /proc/mtrr are suggested to use above interfaces. | ||
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| Drivers should use ioremap_[uc|wc] to access PCI BARs with [uc|wc] access | ||
| types. | ||
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| Drivers should use set_memory_[uc|wc] to set access type for RAM ranges. | ||
|
|
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