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// SPDX-License-Identifier: GPL-2.0
/*
* Handle caching attributes in page tables (PAT)
*
* Authors: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
* Suresh B Siddha <suresh.b.siddha@intel.com>
*
* Interval tree used to store the PAT memory type reservations.
*/
#include <linux/seq_file.h>
#include <linux/debugfs.h>
#include <linux/kernel.h>
#include <linux/interval_tree_generic.h>
#include <linux/sched.h>
#include <linux/gfp.h>
#include <asm/pgtable.h>
#include <asm/memtype.h>
#include "memtype.h"
/*
* The memtype tree keeps track of memory type for specific
* physical memory areas. Without proper tracking, conflicting memory
* types in different mappings can cause CPU cache corruption.
*
* The tree is an interval tree (augmented rbtree) which tree is ordered
* by the starting address. The tree can contain multiple entries for
* different regions which overlap. All the aliases have the same
* cache attributes of course, as enforced by the PAT logic.
*
* memtype_lock protects the rbtree.
*/
static inline u64 interval_start(struct memtype *entry)
{
return entry->start;
}
static inline u64 interval_end(struct memtype *entry)
{
return entry->end - 1;
}
INTERVAL_TREE_DEFINE(struct memtype, rb, u64, subtree_max_end,
interval_start, interval_end,
static, interval)
static struct rb_root_cached memtype_rbroot = RB_ROOT_CACHED;
enum {
MEMTYPE_EXACT_MATCH = 0,
MEMTYPE_END_MATCH = 1
};
static struct memtype *memtype_match(u64 start, u64 end, int match_type)
{
struct memtype *entry_match;
entry_match = interval_iter_first(&memtype_rbroot, start, end-1);
while (entry_match != NULL && entry_match->start < end) {
if ((match_type == MEMTYPE_EXACT_MATCH) &&
(entry_match->start == start) && (entry_match->end == end))
return entry_match;
if ((match_type == MEMTYPE_END_MATCH) &&
(entry_match->start < start) && (entry_match->end == end))
return entry_match;
entry_match = interval_iter_next(entry_match, start, end-1);
}
return NULL; /* Returns NULL if there is no match */
}
static int memtype_check_conflict(u64 start, u64 end,
enum page_cache_mode reqtype,
enum page_cache_mode *newtype)
{
struct memtype *entry_match;
enum page_cache_mode found_type = reqtype;
entry_match = interval_iter_first(&memtype_rbroot, start, end-1);
if (entry_match == NULL)
goto success;
if (entry_match->type != found_type && newtype == NULL)
goto failure;
dprintk("Overlap at 0x%Lx-0x%Lx\n", entry_match->start, entry_match->end);
found_type = entry_match->type;
entry_match = interval_iter_next(entry_match, start, end-1);
while (entry_match) {
if (entry_match->type != found_type)
goto failure;
entry_match = interval_iter_next(entry_match, start, end-1);
}
success:
if (newtype)
*newtype = found_type;
return 0;
failure:
pr_info("x86/PAT: %s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
current->comm, current->pid, start, end,
cattr_name(found_type), cattr_name(entry_match->type));
return -EBUSY;
}
int memtype_check_insert(struct memtype *entry_new, enum page_cache_mode *ret_type)
{
int err = 0;
err = memtype_check_conflict(entry_new->start, entry_new->end, entry_new->type, ret_type);
if (err)
return err;
if (ret_type)
entry_new->type = *ret_type;
interval_insert(entry_new, &memtype_rbroot);
return 0;
}
struct memtype *memtype_erase(u64 start, u64 end)
{
struct memtype *entry_old;
/*
* Since the memtype_rbroot tree allows overlapping ranges,
* memtype_erase() checks with EXACT_MATCH first, i.e. free
* a whole node for the munmap case. If no such entry is found,
* it then checks with END_MATCH, i.e. shrink the size of a node
* from the end for the mremap case.
*/
entry_old = memtype_match(start, end, MEMTYPE_EXACT_MATCH);
if (!entry_old) {
entry_old = memtype_match(start, end, MEMTYPE_END_MATCH);
if (!entry_old)
return ERR_PTR(-EINVAL);
}
if (entry_old->start == start) {
/* munmap: erase this node */
interval_remove(entry_old, &memtype_rbroot);
} else {
/* mremap: update the end value of this node */
interval_remove(entry_old, &memtype_rbroot);
entry_old->end = start;
interval_insert(entry_old, &memtype_rbroot);
return NULL;
}
return entry_old;
}
struct memtype *memtype_lookup(u64 addr)
{
return interval_iter_first(&memtype_rbroot, addr, addr + PAGE_SIZE-1);
}
/*
* Debugging helper, copy the Nth entry of the tree into a
* a copy for printout. This allows us to print out the tree
* via debugfs, without holding the memtype_lock too long:
*/
#ifdef CONFIG_DEBUG_FS
int memtype_copy_nth_element(struct memtype *entry_out, loff_t pos)
{
struct memtype *entry_match;
int i = 1;
entry_match = interval_iter_first(&memtype_rbroot, 0, ULONG_MAX);
while (entry_match && pos != i) {
entry_match = interval_iter_next(entry_match, 0, ULONG_MAX);
i++;
}
if (entry_match) { /* pos == i */
*entry_out = *entry_match;
return 0;
} else {
return 1;
}
}
#endif
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