x86: PAT infrastructure patch
Sets up pat_init() infrastructure.
PAT MSR has following setting.
PAT
|PCD
||PWT
|||
000 WB _PAGE_CACHE_WB
001 WC _PAGE_CACHE_WC
010 UC- _PAGE_CACHE_UC_MINUS
011 UC _PAGE_CACHE_UC
We are effectively changing WT from boot time setting to WC.
UC_MINUS is used to provide backward compatibility to existing /dev/mem
users(X).
reserve_memtype and free_memtype are new interfaces for maintaining alias-free
mapping. It is currently implemented in a simple way with a linked list and
not optimized. reserve and free tracks the effective memory type, as a result
of PAT and MTRR setting rather than what is actually requested in PAT.
pat_init piggy backs on mtrr_init as the rules for setting both pat and mtrr
are same.
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
new file mode 100644
index 0000000..7cc71d8
--- /dev/null
+++ b/arch/x86/mm/pat.c
@@ -0,0 +1,402 @@
+/*
+ * 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/mm.h>
+#include <linux/kernel.h>
+#include <linux/gfp.h>
+#include <linux/fs.h>
+
+#include <asm/msr.h>
+#include <asm/tlbflush.h>
+#include <asm/processor.h>
+#include <asm/pgtable.h>
+#include <asm/pat.h>
+#include <asm/e820.h>
+#include <asm/cacheflush.h>
+#include <asm/fcntl.h>
+#include <asm/mtrr.h>
+
+int pat_wc_enabled = 1;
+
+static u64 __read_mostly boot_pat_state;
+
+static int nopat(char *str)
+{
+ pat_wc_enabled = 0;
+ printk(KERN_INFO "x86: PAT support disabled.\n");
+
+ return 0;
+}
+early_param("nopat", nopat);
+
+static int pat_known_cpu(void)
+{
+ if (!pat_wc_enabled)
+ return 0;
+
+ if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
+ (boot_cpu_data.x86 == 0xF ||
+ (boot_cpu_data.x86 == 6 && boot_cpu_data.x86_model >= 15))) {
+ if (cpu_has_pat) {
+ return 1;
+ }
+ }
+
+ pat_wc_enabled = 0;
+ printk(KERN_INFO "CPU and/or kernel does not support PAT.\n");
+ return 0;
+}
+
+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;
+
+#ifndef CONFIG_X86_PAT
+ nopat(NULL);
+#endif
+
+ /* Boot CPU enables PAT based on CPU feature */
+ if (!smp_processor_id() && !pat_known_cpu())
+ return;
+
+ /* APs enable PAT iff boot CPU has enabled it before */
+ if (smp_processor_id() && !pat_wc_enabled)
+ return;
+
+ /* 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 (!smp_processor_id()) {
+ 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 int pat_x_mtrr_type(u64 start, u64 end, unsigned long prot,
+ unsigned long *ret_prot)
+{
+ unsigned long pat_type;
+ u8 mtrr_type;
+
+ mtrr_type = mtrr_type_lookup(start, end);
+ if (mtrr_type == 0xFF) { /* MTRR not enabled */
+ *ret_prot = prot;
+ return 0;
+ }
+ if (mtrr_type == 0xFE) { /* MTRR match error */
+ *ret_prot = _PAGE_CACHE_UC;
+ return -1;
+ }
+ if (mtrr_type != MTRR_TYPE_UNCACHABLE &&
+ mtrr_type != MTRR_TYPE_WRBACK &&
+ mtrr_type != MTRR_TYPE_WRCOMB) { /* MTRR type unhandled */
+ *ret_prot = _PAGE_CACHE_UC;
+ return -1;
+ }
+
+ pat_type = prot & _PAGE_CACHE_MASK;
+ prot &= (~_PAGE_CACHE_MASK);
+
+ /* Currently doing intersection by hand. Optimize it later. */
+ if (pat_type == _PAGE_CACHE_WC) {
+ *ret_prot = prot | _PAGE_CACHE_WC;
+ } else if (pat_type == _PAGE_CACHE_UC_MINUS) {
+ *ret_prot = prot | _PAGE_CACHE_UC_MINUS;
+ } else if (pat_type == _PAGE_CACHE_UC ||
+ mtrr_type == MTRR_TYPE_UNCACHABLE) {
+ *ret_prot = prot | _PAGE_CACHE_UC;
+ } else if (mtrr_type == MTRR_TYPE_WRCOMB) {
+ *ret_prot = prot | _PAGE_CACHE_WC;
+ } else {
+ *ret_prot = prot | _PAGE_CACHE_WB;
+ }
+
+ return 0;
+}
+
+int reserve_memtype(u64 start, u64 end, unsigned long req_type,
+ unsigned long *ret_type)
+{
+ struct memtype *new_entry = NULL;
+ struct memtype *parse;
+ unsigned long actual_type;
+ int err = 0;
+
+ /* Only track when pat_wc_enabled */
+ if (!pat_wc_enabled) {
+ if (ret_type)
+ *ret_type = req_type;
+
+ return 0;
+ }
+
+ /* Low ISA region is always mapped WB in page table. No need to track */
+ if (start >= ISA_START_ADDRESS && (end - 1) <= ISA_END_ADDRESS) {
+ if (ret_type)
+ *ret_type = _PAGE_CACHE_WB;
+
+ return 0;
+ }
+
+ req_type &= _PAGE_CACHE_MASK;
+ err = pat_x_mtrr_type(start, end, req_type, &actual_type);
+ if (err) {
+ if (ret_type)
+ *ret_type = actual_type;
+
+ return -EINVAL;
+ }
+
+ new_entry = kmalloc(sizeof(struct memtype), GFP_KERNEL);
+ if (!new_entry)
+ return -ENOMEM;
+
+ new_entry->start = start;
+ new_entry->end = end;
+ new_entry->type = actual_type;
+
+ if (ret_type)
+ *ret_type = actual_type;
+
+ spin_lock(&memtype_lock);
+
+ /* Search for existing mapping that overlaps the current range */
+ list_for_each_entry(parse, &memtype_list, nd) {
+ struct memtype *saved_ptr;
+
+ if (parse->start >= end) {
+ list_add(&new_entry->nd, parse->nd.prev);
+ new_entry = NULL;
+ break;
+ }
+
+ if (start <= parse->start && end >= parse->start) {
+ if (actual_type != parse->type && ret_type) {
+ actual_type = parse->type;
+ *ret_type = actual_type;
+ new_entry->type = actual_type;
+ }
+
+ if (actual_type != parse->type) {
+ printk(
+ KERN_INFO "%s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
+ current->comm, current->pid,
+ start, end,
+ cattr_name(actual_type),
+ cattr_name(parse->type));
+ err = -EBUSY;
+ break;
+ }
+
+ saved_ptr = parse;
+ /*
+ * Check to see whether the request overlaps more
+ * than one entry in the list
+ */
+ list_for_each_entry_continue(parse, &memtype_list, nd) {
+ if (end <= parse->start) {
+ break;
+ }
+
+ if (actual_type != parse->type) {
+ printk(
+ KERN_INFO "%s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
+ current->comm, current->pid,
+ start, end,
+ cattr_name(actual_type),
+ cattr_name(parse->type));
+ err = -EBUSY;
+ break;
+ }
+ }
+
+ if (err) {
+ break;
+ }
+
+ /* No conflict. Go ahead and add this new entry */
+ list_add(&new_entry->nd, saved_ptr->nd.prev);
+ new_entry = NULL;
+ break;
+ }
+
+ if (start < parse->end) {
+ if (actual_type != parse->type && ret_type) {
+ actual_type = parse->type;
+ *ret_type = actual_type;
+ new_entry->type = actual_type;
+ }
+
+ if (actual_type != parse->type) {
+ printk(
+ KERN_INFO "%s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
+ current->comm, current->pid,
+ start, end,
+ cattr_name(actual_type),
+ cattr_name(parse->type));
+ err = -EBUSY;
+ break;
+ }
+
+ saved_ptr = parse;
+ /*
+ * Check to see whether the request overlaps more
+ * than one entry in the list
+ */
+ list_for_each_entry_continue(parse, &memtype_list, nd) {
+ if (end <= parse->start) {
+ break;
+ }
+
+ if (actual_type != parse->type) {
+ printk(
+ KERN_INFO "%s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
+ current->comm, current->pid,
+ start, end,
+ cattr_name(actual_type),
+ cattr_name(parse->type));
+ err = -EBUSY;
+ break;
+ }
+ }
+
+ if (err) {
+ break;
+ }
+
+ /* No conflict. Go ahead and add this new entry */
+ list_add(&new_entry->nd, &saved_ptr->nd);
+ new_entry = NULL;
+ break;
+ }
+ }
+
+ if (err) {
+ kfree(new_entry);
+ spin_unlock(&memtype_lock);
+ return err;
+ }
+
+ if (new_entry) {
+ /* No conflict. Not yet added to the list. Add to the tail */
+ list_add_tail(&new_entry->nd, &memtype_list);
+ }
+
+ spin_unlock(&memtype_lock);
+ return err;
+}
+
+int free_memtype(u64 start, u64 end)
+{
+ struct memtype *ml;
+ int err = -EINVAL;
+
+ /* Only track when pat_wc_enabled */
+ if (!pat_wc_enabled) {
+ return 0;
+ }
+
+ /* Low ISA region is always mapped WB. No need to track */
+ if (start >= ISA_START_ADDRESS && end <= ISA_END_ADDRESS) {
+ return 0;
+ }
+
+ spin_lock(&memtype_lock);
+ list_for_each_entry(ml, &memtype_list, nd) {
+ if (ml->start == start && ml->end == end) {
+ list_del(&ml->nd);
+ kfree(ml);
+ err = 0;
+ break;
+ }
+ }
+ spin_unlock(&memtype_lock);
+
+ if (err) {
+ printk(KERN_DEBUG "%s:%d freeing invalid memtype %Lx-%Lx\n",
+ current->comm, current->pid, start, end);
+ }
+ return err;
+}
+