Commit 2e5d9c85 authored by venkatesh.pallipadi@intel.com's avatar venkatesh.pallipadi@intel.com Committed by Ingo Molnar
Browse files

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: default avatarVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: default avatarSuresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent d27554d8

arch/x86/Kconfig

+15 −0
Original line number Diff line number Diff line
@@ -1009,6 +1009,21 @@ config MTRR 


	  See <file:Documentation/mtrr.txt> for more information.



config X86_PAT

	def_bool y

	prompt "x86 PAT support"

	depends on MTRR && NONPROMISC_DEVMEM

	help

	  Use PAT attributes to setup page level cache control.

	---help---

	  PATs are the modern equivalents of MTRRs and are much more

	  flexible than MTRRs.



	  Say N here if you see bootup problems (boot crash, boot hang,

	  spontaneous reboots) or a non-working Xorg.



	  If unsure, say Y.



config EFI

	def_bool n

	prompt "EFI runtime service support"

arch/x86/kernel/cpu/mtrr/generic.c

+120 −0
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ 
#include <asm/cpufeature.h>

#include <asm/processor-flags.h>

#include <asm/tlbflush.h>

#include <asm/pat.h>

#include "mtrr.h"



struct mtrr_state {
@@ -35,6 +36,7 @@ static struct fixed_range_block fixed_range_blocks[] = { 


static unsigned long smp_changes_mask;

static struct mtrr_state mtrr_state = {};

static int mtrr_state_set;



#undef MODULE_PARAM_PREFIX

#define MODULE_PARAM_PREFIX "mtrr."
@@ -42,6 +44,106 @@ static struct mtrr_state mtrr_state = {}; 
static int mtrr_show;

module_param_named(show, mtrr_show, bool, 0);



/*

 * Returns the effective MTRR type for the region

 * Error returns:

 * - 0xFE - when the range is "not entirely covered" by _any_ var range MTRR

 * - 0xFF - when MTRR is not enabled

 */

u8 mtrr_type_lookup(u64 start, u64 end)

{

	int i;

	u64 base, mask;

	u8 prev_match, curr_match;



	if (!mtrr_state_set)

		return 0xFF;



	if (!mtrr_state.enabled)

		return 0xFF;



	/* Make end inclusive end, instead of exclusive */

	end--;



	/* Look in fixed ranges. Just return the type as per start */

	if (mtrr_state.have_fixed && (start < 0x100000)) {

		int idx;



		if (start < 0x80000) {

			idx = 0;

			idx += (start >> 16);

			return mtrr_state.fixed_ranges[idx];

		} else if (start < 0xC0000) {

			idx = 1 * 8;

			idx += ((start - 0x80000) >> 14);

			return mtrr_state.fixed_ranges[idx];

		} else if (start < 0x1000000) {

			idx = 3 * 8;

			idx += ((start - 0xC0000) >> 12);

			return mtrr_state.fixed_ranges[idx];

		}

	}



	/*

	 * Look in variable ranges

	 * Look of multiple ranges matching this address and pick type

	 * as per MTRR precedence

	 */

	if (!mtrr_state.enabled & 2) {

		return mtrr_state.def_type;

	}



	prev_match = 0xFF;

	for (i = 0; i < num_var_ranges; ++i) {

		unsigned short start_state, end_state;



		if (!(mtrr_state.var_ranges[i].mask_lo & (1 << 11)))

			continue;



		base = (((u64)mtrr_state.var_ranges[i].base_hi) << 32) +

		       (mtrr_state.var_ranges[i].base_lo & PAGE_MASK);

		mask = (((u64)mtrr_state.var_ranges[i].mask_hi) << 32) +

		       (mtrr_state.var_ranges[i].mask_lo & PAGE_MASK);



		start_state = ((start & mask) == (base & mask));

		end_state = ((end & mask) == (base & mask));

		if (start_state != end_state)

			return 0xFE;



		if ((start & mask) != (base & mask)) {

			continue;

		}



		curr_match = mtrr_state.var_ranges[i].base_lo & 0xff;

		if (prev_match == 0xFF) {

			prev_match = curr_match;

			continue;

		}



		if (prev_match == MTRR_TYPE_UNCACHABLE ||

		    curr_match == MTRR_TYPE_UNCACHABLE) {

			return MTRR_TYPE_UNCACHABLE;

		}



		if ((prev_match == MTRR_TYPE_WRBACK &&

		     curr_match == MTRR_TYPE_WRTHROUGH) ||

		    (prev_match == MTRR_TYPE_WRTHROUGH &&

		     curr_match == MTRR_TYPE_WRBACK)) {

			prev_match = MTRR_TYPE_WRTHROUGH;

			curr_match = MTRR_TYPE_WRTHROUGH;

		}



		if (prev_match != curr_match) {

			return MTRR_TYPE_UNCACHABLE;

		}

	}



	if (prev_match != 0xFF)

		return prev_match;



	return mtrr_state.def_type;

}



/*  Get the MSR pair relating to a var range  */

static void

get_mtrr_var_range(unsigned int index, struct mtrr_var_range *vr)
@@ -79,12 +181,16 @@ static void print_fixed(unsigned base, unsigned step, const mtrr_type*types) 
			base, base + step - 1, mtrr_attrib_to_str(*types));

}



static void prepare_set(void);

static void post_set(void);



/*  Grab all of the MTRR state for this CPU into *state  */

void __init get_mtrr_state(void)

{

	unsigned int i;

	struct mtrr_var_range *vrs;

	unsigned lo, dummy;

	unsigned long flags;



	vrs = mtrr_state.var_ranges;
@@ -131,6 +237,17 @@ void __init get_mtrr_state(void) 
				printk(KERN_INFO "MTRR %u disabled\n", i);

		}

	}

	mtrr_state_set = 1;



	/* PAT setup for BP. We need to go through sync steps here */

	local_irq_save(flags);

	prepare_set();



	pat_init();



	post_set();

	local_irq_restore(flags);



}



/*  Some BIOS's are fucked and don't set all MTRRs the same!  */
@@ -397,6 +514,9 @@ static void generic_set_all(void) 
	/* Actually set the state */

	mask = set_mtrr_state();



	/* also set PAT */

	pat_init();



	post_set();

	local_irq_restore(flags);

arch/x86/mm/Makefile

+2 −1
Original line number Diff line number Diff line 
obj-y	:=  init_$(BITS).o fault.o ioremap.o extable.o pageattr.o mmap.o

obj-y	:=  init_$(BITS).o fault.o ioremap.o extable.o pageattr.o mmap.o \

	    pat.o



obj-$(CONFIG_X86_32)		+= pgtable_32.o

arch/x86/mm/pageattr.c

+2 −2
Original line number Diff line number Diff line
@@ -773,14 +773,14 @@ static inline int change_page_attr_clear(unsigned long addr, int numpages, 
int set_memory_uc(unsigned long addr, int numpages)

{

	return change_page_attr_set(addr, numpages,

				    __pgprot(_PAGE_PCD));

				    __pgprot(_PAGE_CACHE_UC));

}

EXPORT_SYMBOL(set_memory_uc);



int set_memory_wb(unsigned long addr, int numpages)

{

	return change_page_attr_clear(addr, numpages,

				      __pgprot(_PAGE_PCD | _PAGE_PWT));

				      __pgprot(_PAGE_CACHE_MASK));

}

EXPORT_SYMBOL(set_memory_wb);

arch/x86/mm/pat.c

0 → 100644
+402 −0
Original line number Diff line number Diff line 
/*

 * 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;

}

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