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DEFINITIONS
This source file includes following definitions.
- pat_disable
- nopat
- pat_debug_setup
- pat_init
- cattr_name
- pat_x_mtrr_type
- chk_conflict
- reserve_ram_pages_type
- free_ram_pages_type
- reserve_memtype
- free_memtype
- phys_mem_access_prot
- range_is_allowed
- range_is_allowed
- phys_mem_access_prot_allowed
- map_devmem
- unmap_devmem
- memtype_get_idx
- memtype_seq_start
- memtype_seq_next
- memtype_seq_stop
- memtype_seq_show
- memtype_seq_open
- pat_memtype_list_init
/*
* Handle caching attributes in page tables (PAT)
*
* Authors: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
* Suresh B Siddha <suresh.b.siddha@intel.com>
*
* Loosely based on earlier PAT patchset from Eric Biederman and Andi Kleen.
*/
#include <linux/seq_file.h>
#include <linux/bootmem.h>
#include <linux/debugfs.h>
#include <linux/kernel.h>
#include <linux/gfp.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <asm/cacheflush.h>
#include <asm/processor.h>
#include <asm/tlbflush.h>
#include <asm/pgtable.h>
#include <asm/fcntl.h>
#include <asm/e820.h>
#include <asm/mtrr.h>
#include <asm/page.h>
#include <asm/msr.h>
#include <asm/pat.h>
#include <asm/io.h>
#ifdef CONFIG_X86_PAT
int __read_mostly pat_enabled = 1;
void __cpuinit pat_disable(char *reason)
{
pat_enabled = 0;
printk(KERN_INFO "%s\n", reason);
}
static int __init nopat(char *str)
{
pat_disable("PAT support disabled.");
return 0;
}
early_param("nopat", nopat);
#endif
static int debug_enable;
static int __init pat_debug_setup(char *str)
{
debug_enable = 1;
return 0;
}
__setup("debugpat", pat_debug_setup);
#define dprintk(fmt, arg...) \
do { if (debug_enable) printk(KERN_INFO fmt, ##arg); } while (0)
static u64 __read_mostly boot_pat_state;
enum {
PAT_UC = 0, /* uncached */
PAT_WC = 1, /* Write combining */
PAT_WT = 4, /* Write Through */
PAT_WP = 5, /* Write Protected */
PAT_WB = 6, /* Write Back (default) */
PAT_UC_MINUS = 7, /* UC, but can be overriden by MTRR */
};
#define PAT(x, y) ((u64)PAT_ ## y << ((x)*8))
void pat_init(void)
{
u64 pat;
if (!pat_enabled)
return;
/* Paranoia check. */
if (!cpu_has_pat && boot_pat_state) {
/*
* If this happens we are on a secondary CPU, but
* switched to PAT on the boot CPU. We have no way to
* undo PAT.
*/
printk(KERN_ERR "PAT enabled, "
"but not supported by secondary CPU\n");
BUG();
}
/* Set PWT to Write-Combining. All other bits stay the same */
/*
* PTE encoding used in Linux:
* PAT
* |PCD
* ||PWT
* |||
* 000 WB _PAGE_CACHE_WB
* 001 WC _PAGE_CACHE_WC
* 010 UC- _PAGE_CACHE_UC_MINUS
* 011 UC _PAGE_CACHE_UC
* PAT bit unused
*/
pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC);
/* Boot CPU check */
if (!boot_pat_state)
rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
wrmsrl(MSR_IA32_CR_PAT, pat);
printk(KERN_INFO "x86 PAT enabled: cpu %d, old 0x%Lx, new 0x%Lx\n",
smp_processor_id(), boot_pat_state, pat);
}
#undef PAT
static char *cattr_name(unsigned long flags)
{
switch (flags & _PAGE_CACHE_MASK) {
case _PAGE_CACHE_UC: return "uncached";
case _PAGE_CACHE_UC_MINUS: return "uncached-minus";
case _PAGE_CACHE_WB: return "write-back";
case _PAGE_CACHE_WC: return "write-combining";
default: return "broken";
}
}
/*
* The global memtype list keeps track of memory type for specific
* physical memory areas. Conflicting memory types in different
* mappings can cause CPU cache corruption. To avoid this we keep track.
*
* The list is sorted based on starting address and can contain multiple
* entries for each address (this allows reference counting for overlapping
* areas). All the aliases have the same cache attributes of course.
* Zero attributes are represented as holes.
*
* Currently the data structure is a list because the number of mappings
* are expected to be relatively small. If this should be a problem
* it could be changed to a rbtree or similar.
*
* memtype_lock protects the whole list.
*/
struct memtype {
u64 start;
u64 end;
unsigned long type;
struct list_head nd;
};
static LIST_HEAD(memtype_list);
static DEFINE_SPINLOCK(memtype_lock); /* protects memtype list */
/*
* Does intersection of PAT memory type and MTRR memory type and returns
* the resulting memory type as PAT understands it.
* (Type in pat and mtrr will not have same value)
* The intersection is based on "Effective Memory Type" tables in IA-32
* SDM vol 3a
*/
static unsigned long pat_x_mtrr_type(u64 start, u64 end, unsigned long req_type)
{
/*
* Look for MTRR hint to get the effective type in case where PAT
* request is for WB.
*/
if (req_type == _PAGE_CACHE_WB) {
u8 mtrr_type;
mtrr_type = mtrr_type_lookup(start, end);
if (mtrr_type == MTRR_TYPE_UNCACHABLE)
return _PAGE_CACHE_UC;
if (mtrr_type == MTRR_TYPE_WRCOMB)
return _PAGE_CACHE_WC;
}
return req_type;
}
static int
chk_conflict(struct memtype *new, struct memtype *entry, unsigned long *type)
{
if (new->type != entry->type) {
if (type) {
new->type = entry->type;
*type = entry->type;
} else
goto conflict;
}
/* check overlaps with more than one entry in the list */
list_for_each_entry_continue(entry, &memtype_list, nd) {
if (new->end <= entry->start)
break;
else if (new->type != entry->type)
goto conflict;
}
return 0;
conflict:
printk(KERN_INFO "%s:%d conflicting memory types "
"%Lx-%Lx %s<->%s\n", current->comm, current->pid, new->start,
new->end, cattr_name(new->type), cattr_name(entry->type));
return -EBUSY;
}
static struct memtype *cached_entry;
static u64 cached_start;
/*
* For RAM pages, mark the pages as non WB memory type using
* PageNonWB (PG_arch_1). We allow only one set_memory_uc() or
* set_memory_wc() on a RAM page at a time before marking it as WB again.
* This is ok, because only one driver will be owning the page and
* doing set_memory_*() calls.
*
* For now, we use PageNonWB to track that the RAM page is being mapped
* as non WB. In future, we will have to use one more flag
* (or some other mechanism in page_struct) to distinguish between
* UC and WC mapping.
*/
static int reserve_ram_pages_type(u64 start, u64 end, unsigned long req_type,
unsigned long *new_type)
{
struct page *page;
u64 pfn, end_pfn;
for (pfn = (start >> PAGE_SHIFT); pfn < (end >> PAGE_SHIFT); ++pfn) {
page = pfn_to_page(pfn);
if (page_mapped(page) || PageNonWB(page))
goto out;
SetPageNonWB(page);
}
return 0;
out:
end_pfn = pfn;
for (pfn = (start >> PAGE_SHIFT); pfn < end_pfn; ++pfn) {
page = pfn_to_page(pfn);
ClearPageNonWB(page);
}
return -EINVAL;
}
static int free_ram_pages_type(u64 start, u64 end)
{
struct page *page;
u64 pfn, end_pfn;
for (pfn = (start >> PAGE_SHIFT); pfn < (end >> PAGE_SHIFT); ++pfn) {
page = pfn_to_page(pfn);
if (page_mapped(page) || !PageNonWB(page))
goto out;
ClearPageNonWB(page);
}
return 0;
out:
end_pfn = pfn;
for (pfn = (start >> PAGE_SHIFT); pfn < end_pfn; ++pfn) {
page = pfn_to_page(pfn);
SetPageNonWB(page);
}
return -EINVAL;
}
/*
* req_type typically has one of the:
* - _PAGE_CACHE_WB
* - _PAGE_CACHE_WC
* - _PAGE_CACHE_UC_MINUS
* - _PAGE_CACHE_UC
*
* req_type will have a special case value '-1', when requester want to inherit
* the memory type from mtrr (if WB), existing PAT, defaulting to UC_MINUS.
*
* If new_type is NULL, function will return an error if it cannot reserve the
* region with req_type. If new_type is non-NULL, function will return
* available type in new_type in case of no error. In case of any error
* it will return a negative return value.
*/
int reserve_memtype(u64 start, u64 end, unsigned long req_type,
unsigned long *new_type)
{
struct memtype *new, *entry;
unsigned long actual_type;
struct list_head *where;
int is_range_ram;
int err = 0;
BUG_ON(start >= end); /* end is exclusive */
if (!pat_enabled) {
/* This is identical to page table setting without PAT */
if (new_type) {
if (req_type == -1)
*new_type = _PAGE_CACHE_WB;
else
*new_type = req_type & _PAGE_CACHE_MASK;
}
return 0;
}
/* Low ISA region is always mapped WB in page table. No need to track */
if (is_ISA_range(start, end - 1)) {
if (new_type)
*new_type = _PAGE_CACHE_WB;
return 0;
}
if (req_type == -1) {
/*
* Call mtrr_lookup to get the type hint. This is an
* optimization for /dev/mem mmap'ers into WB memory (BIOS
* tools and ACPI tools). Use WB request for WB memory and use
* UC_MINUS otherwise.
*/
u8 mtrr_type = mtrr_type_lookup(start, end);
if (mtrr_type == MTRR_TYPE_WRBACK)
actual_type = _PAGE_CACHE_WB;
else
actual_type = _PAGE_CACHE_UC_MINUS;
} else {
actual_type = pat_x_mtrr_type(start, end,
req_type & _PAGE_CACHE_MASK);
}
is_range_ram = pagerange_is_ram(start, end);
if (is_range_ram == 1)
return reserve_ram_pages_type(start, end, req_type, new_type);
else if (is_range_ram < 0)
return -EINVAL;
new = kmalloc(sizeof(struct memtype), GFP_KERNEL);
if (!new)
return -ENOMEM;
new->start = start;
new->end = end;
new->type = actual_type;
if (new_type)
*new_type = actual_type;
spin_lock(&memtype_lock);
if (cached_entry && start >= cached_start)
entry = cached_entry;
else
entry = list_entry(&memtype_list, struct memtype, nd);
/* Search for existing mapping that overlaps the current range */
where = NULL;
list_for_each_entry_continue(entry, &memtype_list, nd) {
if (end <= entry->start) {
where = entry->nd.prev;
cached_entry = list_entry(where, struct memtype, nd);
break;
} else if (start <= entry->start) { /* end > entry->start */
err = chk_conflict(new, entry, new_type);
if (!err) {
dprintk("Overlap at 0x%Lx-0x%Lx\n",
entry->start, entry->end);
where = entry->nd.prev;
cached_entry = list_entry(where,
struct memtype, nd);
}
break;
} else if (start < entry->end) { /* start > entry->start */
err = chk_conflict(new, entry, new_type);
if (!err) {
dprintk("Overlap at 0x%Lx-0x%Lx\n",
entry->start, entry->end);
cached_entry = list_entry(entry->nd.prev,
struct memtype, nd);
/*
* Move to right position in the linked
* list to add this new entry
*/
list_for_each_entry_continue(entry,
&memtype_list, nd) {
if (start <= entry->start) {
where = entry->nd.prev;
break;
}
}
}
break;
}
}
if (err) {
printk(KERN_INFO "reserve_memtype failed 0x%Lx-0x%Lx, "
"track %s, req %s\n",
start, end, cattr_name(new->type), cattr_name(req_type));
kfree(new);
spin_unlock(&memtype_lock);
return err;
}
cached_start = start;
if (where)
list_add(&new->nd, where);
else
list_add_tail(&new->nd, &memtype_list);
spin_unlock(&memtype_lock);
dprintk("reserve_memtype added 0x%Lx-0x%Lx, track %s, req %s, ret %s\n",
start, end, cattr_name(new->type), cattr_name(req_type),
new_type ? cattr_name(*new_type) : "-");
return err;
}
int free_memtype(u64 start, u64 end)
{
struct memtype *entry;
int err = -EINVAL;
int is_range_ram;
if (!pat_enabled)
return 0;
/* Low ISA region is always mapped WB. No need to track */
if (is_ISA_range(start, end - 1))
return 0;
is_range_ram = pagerange_is_ram(start, end);
if (is_range_ram == 1)
return free_ram_pages_type(start, end);
else if (is_range_ram < 0)
return -EINVAL;
spin_lock(&memtype_lock);
list_for_each_entry(entry, &memtype_list, nd) {
if (entry->start == start && entry->end == end) {
if (cached_entry == entry || cached_start == start)
cached_entry = NULL;
list_del(&entry->nd);
kfree(entry);
err = 0;
break;
}
}
spin_unlock(&memtype_lock);
if (err) {
printk(KERN_INFO "%s:%d freeing invalid memtype %Lx-%Lx\n",
current->comm, current->pid, start, end);
}
dprintk("free_memtype request 0x%Lx-0x%Lx\n", start, end);
return err;
}
pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
unsigned long size, pgprot_t vma_prot)
{
return vma_prot;
}
#ifdef CONFIG_STRICT_DEVMEM
/* This check is done in drivers/char/mem.c in case of STRICT_DEVMEM*/
static inline int range_is_allowed(unsigned long pfn, unsigned long size)
{
return 1;
}
#else
static inline int range_is_allowed(unsigned long pfn, unsigned long size)
{
u64 from = ((u64)pfn) << PAGE_SHIFT;
u64 to = from + size;
u64 cursor = from;
while (cursor < to) {
if (!devmem_is_allowed(pfn)) {
printk(KERN_INFO
"Program %s tried to access /dev/mem between %Lx->%Lx.\n",
current->comm, from, to);
return 0;
}
cursor += PAGE_SIZE;
pfn++;
}
return 1;
}
#endif /* CONFIG_STRICT_DEVMEM */
int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
unsigned long size, pgprot_t *vma_prot)
{
u64 offset = ((u64) pfn) << PAGE_SHIFT;
unsigned long flags = -1;
int retval;
if (!range_is_allowed(pfn, size))
return 0;
if (file->f_flags & O_SYNC) {
flags = _PAGE_CACHE_UC_MINUS;
}
#ifdef CONFIG_X86_32
/*
* On the PPro and successors, the MTRRs are used to set
* memory types for physical addresses outside main memory,
* so blindly setting UC or PWT on those pages is wrong.
* For Pentiums and earlier, the surround logic should disable
* caching for the high addresses through the KEN pin, but
* we maintain the tradition of paranoia in this code.
*/
if (!pat_enabled &&
!(boot_cpu_has(X86_FEATURE_MTRR) ||
boot_cpu_has(X86_FEATURE_K6_MTRR) ||
boot_cpu_has(X86_FEATURE_CYRIX_ARR) ||
boot_cpu_has(X86_FEATURE_CENTAUR_MCR)) &&
(pfn << PAGE_SHIFT) >= __pa(high_memory)) {
flags = _PAGE_CACHE_UC;
}
#endif
/*
* With O_SYNC, we can only take UC_MINUS mapping. Fail if we cannot.
*
* Without O_SYNC, we want to get
* - WB for WB-able memory and no other conflicting mappings
* - UC_MINUS for non-WB-able memory with no other conflicting mappings
* - Inherit from confliting mappings otherwise
*/
if (flags != -1) {
retval = reserve_memtype(offset, offset + size, flags, NULL);
} else {
retval = reserve_memtype(offset, offset + size, -1, &flags);
}
if (retval < 0)
return 0;
if (((pfn < max_low_pfn_mapped) ||
(pfn >= (1UL<<(32 - PAGE_SHIFT)) && pfn < max_pfn_mapped)) &&
ioremap_change_attr((unsigned long)__va(offset), size, flags) < 0) {
free_memtype(offset, offset + size);
printk(KERN_INFO
"%s:%d /dev/mem ioremap_change_attr failed %s for %Lx-%Lx\n",
current->comm, current->pid,
cattr_name(flags),
offset, (unsigned long long)(offset + size));
return 0;
}
*vma_prot = __pgprot((pgprot_val(*vma_prot) & ~_PAGE_CACHE_MASK) |
flags);
return 1;
}
void map_devmem(unsigned long pfn, unsigned long size, pgprot_t vma_prot)
{
unsigned long want_flags = (pgprot_val(vma_prot) & _PAGE_CACHE_MASK);
u64 addr = (u64)pfn << PAGE_SHIFT;
unsigned long flags;
reserve_memtype(addr, addr + size, want_flags, &flags);
if (flags != want_flags) {
printk(KERN_INFO
"%s:%d /dev/mem expected mapping type %s for %Lx-%Lx, got %s\n",
current->comm, current->pid,
cattr_name(want_flags),
addr, (unsigned long long)(addr + size),
cattr_name(flags));
}
}
void unmap_devmem(unsigned long pfn, unsigned long size, pgprot_t vma_prot)
{
u64 addr = (u64)pfn << PAGE_SHIFT;
free_memtype(addr, addr + size);
}
#if defined(CONFIG_DEBUG_FS) && defined(CONFIG_X86_PAT)
/* get Nth element of the linked list */
static struct memtype *memtype_get_idx(loff_t pos)
{
struct memtype *list_node, *print_entry;
int i = 1;
print_entry = kmalloc(sizeof(struct memtype), GFP_KERNEL);
if (!print_entry)
return NULL;
spin_lock(&memtype_lock);
list_for_each_entry(list_node, &memtype_list, nd) {
if (pos == i) {
*print_entry = *list_node;
spin_unlock(&memtype_lock);
return print_entry;
}
++i;
}
spin_unlock(&memtype_lock);
kfree(print_entry);
return NULL;
}
static void *memtype_seq_start(struct seq_file *seq, loff_t *pos)
{
if (*pos == 0) {
++*pos;
seq_printf(seq, "PAT memtype list:\n");
}
return memtype_get_idx(*pos);
}
static void *memtype_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
++*pos;
return memtype_get_idx(*pos);
}
static void memtype_seq_stop(struct seq_file *seq, void *v)
{
}
static int memtype_seq_show(struct seq_file *seq, void *v)
{
struct memtype *print_entry = (struct memtype *)v;
seq_printf(seq, "%s @ 0x%Lx-0x%Lx\n", cattr_name(print_entry->type),
print_entry->start, print_entry->end);
kfree(print_entry);
return 0;
}
static struct seq_operations memtype_seq_ops = {
.start = memtype_seq_start,
.next = memtype_seq_next,
.stop = memtype_seq_stop,
.show = memtype_seq_show,
};
static int memtype_seq_open(struct inode *inode, struct file *file)
{
return seq_open(file, &memtype_seq_ops);
}
static const struct file_operations memtype_fops = {
.open = memtype_seq_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release,
};
static int __init pat_memtype_list_init(void)
{
debugfs_create_file("pat_memtype_list", S_IRUSR, arch_debugfs_dir,
NULL, &memtype_fops);
return 0;
}
late_initcall(pat_memtype_list_init);
#endif /* CONFIG_DEBUG_FS && CONFIG_X86_PAT */