aboutsummaryrefslogtreecommitdiffstats
path: root/target/linux/layerscape/patches-5.4/701-net-0042-sdk_dpaa-ceetm-add-independent-CEETM-congestion-thre.patch
blob: 461280baf6877582c636b9e753d7ef6989ef6cc9 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
From aa54d82b06962bb620852ed20270f7783be68897 Mon Sep 17 00:00:00 2001
From: Camelia Groza <camelia.groza@nxp.com>
Date: Fri, 24 Nov 2017 10:29:12 +0200
Subject: [PATCH] sdk_dpaa: ceetm: add independent CEETM congestion thresholds

Configure the CEETM egress congestion thresholds independently from the
default Ethernet driver's Work Queues. Allow the user to edit the
thresholds through menuconfig.

Signed-off-by: Camelia Groza <camelia.groza@nxp.com>
---
 drivers/net/ethernet/freescale/sdk_dpaa/Kconfig    | 23 ++++++++++++++++++++++
 .../ethernet/freescale/sdk_dpaa/dpaa_eth_ceetm.c   |  4 ++--
 2 files changed, 25 insertions(+), 2 deletions(-)

--- a/drivers/net/ethernet/freescale/sdk_dpaa/Kconfig
+++ b/drivers/net/ethernet/freescale/sdk_dpaa/Kconfig
@@ -20,6 +20,29 @@ config FSL_DPAA_CEETM
 	help
 	Enable QoS offloading support through the CEETM hardware block.
 
+config FSL_DPAA_CEETM_CCS_THRESHOLD_1G
+	hex "CEETM egress congestion threshold on 1G ports"
+	depends on FSL_DPAA_CEETM
+	range 0x1000 0x10000000
+	default "0x000a0000"
+	help
+	  The size in bytes of the CEETM egress Class Congestion State threshold on 1G ports.
+	  The threshold needs to be configured keeping in mind the following factors:
+	       - A threshold too large will buffer frames for a long time in the TX queues,
+	       when a small shaping rate is configured. This will cause buffer pool depletion
+	       or out of memory errors. This in turn will cause frame loss on RX;
+	       - A threshold too small will cause unnecessary frame loss by entering
+	       congestion too often.
+
+config FSL_DPAA_CEETM_CCS_THRESHOLD_10G
+	hex "CEETM egress congestion threshold on 10G ports"
+	depends on FSL_DPAA_CEETM
+	range 0x1000 0x20000000
+	default "0x00640000"
+	help
+	  The size in bytes of the CEETM egress Class Congestion State threshold on 10G ports.
+	  See FSL_DPAA_CEETM_CCS_THRESHOLD_1G for details.
+
 config FSL_DPAA_OFFLINE_PORTS
 	bool "Offline Ports support"
 	depends on FSL_SDK_DPAA_ETH
--- a/drivers/net/ethernet/freescale/sdk_dpaa/dpaa_eth_ceetm.c
+++ b/drivers/net/ethernet/freescale/sdk_dpaa/dpaa_eth_ceetm.c
@@ -185,9 +185,9 @@ static int ceetm_config_ccg(struct qm_ce
 
 	/* Set the congestion state thresholds according to the link speed */
 	if (dpa_priv->mac_dev->if_support & SUPPORTED_10000baseT_Full)
-		cs_th = CONFIG_FSL_DPAA_CS_THRESHOLD_10G;
+		cs_th = CONFIG_FSL_DPAA_CEETM_CCS_THRESHOLD_10G;
 	else
-		cs_th = CONFIG_FSL_DPAA_CS_THRESHOLD_1G;
+		cs_th = CONFIG_FSL_DPAA_CEETM_CCS_THRESHOLD_1G;
 
 	qm_cgr_cs_thres_set64(&ccg_params.cs_thres_in, cs_th, 1);
 	qm_cgr_cs_thres_set64(&ccg_params.cs_thres_out,
'n355' href='#n355'>355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638
/*
 * Two Levels Segregate Fit memory allocator (TLSF)
 * Version 2.3.2
 *
 * Written by Miguel Masmano Tello <mimastel@doctor.upv.es>
 *
 * Thanks to Ismael Ripoll for his suggestions and reviews
 *
 * Copyright (C) 2007, 2006, 2005, 2004
 *
 * This code is released using a dual license strategy: GPL/LGPL
 * You can choose the licence that better fits your requirements.
 *
 * Released under the terms of the GNU General Public License Version 2.0
 * Released under the terms of the GNU Lesser General Public License 
 * Version 2.1
 *
 * This is kernel port of TLSF allocator.
 * Original code can be found at: http://rtportal.upv.es/rtmalloc/
 * Adapted for Linux by Nitin Gupta (nitingupta910@gmail.com)
 * (http://code.google.com/p/compcache/source/browse/trunk/sub-projects
 *  /allocators/tlsf-kmod r229 dated Aug 27, 2008
 * Adapted for Xen by Dan Magenheimer (dan.magenheimer@oracle.com)
 */

#include <xen/config.h>
#include <xen/irq.h>
#include <xen/mm.h>
#include <asm/time.h>

#define MAX_POOL_NAME_LEN       16

/* Some IMPORTANT TLSF parameters */
#define MEM_ALIGN       (sizeof(void *) * 2)
#define MEM_ALIGN_MASK  (~(MEM_ALIGN - 1))

#define MAX_FLI         (30)
#define MAX_LOG2_SLI    (5)
#define MAX_SLI         (1 << MAX_LOG2_SLI)

#define FLI_OFFSET      (6)
/* tlsf structure just will manage blocks bigger than 128 bytes */
#define SMALL_BLOCK     (128)
#define REAL_FLI        (MAX_FLI - FLI_OFFSET)
#define MIN_BLOCK_SIZE  (sizeof(struct free_ptr))
#define BHDR_OVERHEAD   (sizeof(struct bhdr) - MIN_BLOCK_SIZE)

#define PTR_MASK        (sizeof(void *) - 1)
#define BLOCK_SIZE_MASK (0xFFFFFFFF - PTR_MASK)

#define GET_NEXT_BLOCK(addr, r) ((struct bhdr *) \
                                ((char *)(addr) + (r)))
#define ROUNDUP_SIZE(r)         (((r) + MEM_ALIGN - 1) & MEM_ALIGN_MASK)
#define ROUNDDOWN_SIZE(r)       ((r) & MEM_ALIGN_MASK)
#define ROUNDUP_PAGE(r)         (((r) + PAGE_SIZE - 1) & PAGE_MASK)

#define BLOCK_STATE     (0x1)
#define PREV_STATE      (0x2)

/* bit 0 of the block size */
#define FREE_BLOCK      (0x1)
#define USED_BLOCK      (0x0)

/* bit 1 of the block size */
#define PREV_FREE       (0x2)
#define PREV_USED       (0x0)

static spinlock_t pool_list_lock;
static struct list_head pool_list_head;

struct free_ptr {
    struct bhdr *prev;
    struct bhdr *next;
};

struct bhdr {
    /* All blocks in a region are linked in order of physical address */
    struct bhdr *prev_hdr;
    /*
     * The size is stored in bytes
     *  bit 0: block is free, if set
     *  bit 1: previous block is free, if set
     */
    u32 size;
    /* Free blocks in individual freelists are linked */
    union {
        struct free_ptr free_ptr;
        u8 buffer[sizeof(struct free_ptr)];
    } ptr;
};

struct xmem_pool {
    /* First level bitmap (REAL_FLI bits) */
    u32 fl_bitmap;

    /* Second level bitmap */
    u32 sl_bitmap[REAL_FLI];

    /* Free lists */
    struct bhdr *matrix[REAL_FLI][MAX_SLI];

    spinlock_t lock;

    unsigned long init_size;
    unsigned long max_size;
    unsigned long grow_size;

    /* Basic stats */
    unsigned long used_size;
    unsigned long num_regions;

    /* User provided functions for expanding/shrinking pool */
    xmem_pool_get_memory *get_mem;
    xmem_pool_put_memory *put_mem;

    struct list_head list;

    void *init_region;
    char name[MAX_POOL_NAME_LEN];
};

/*
 * Helping functions
 */

/**
 * Returns indexes (fl, sl) of the list used to serve request of size r
 */
static inline void MAPPING_SEARCH(unsigned long *r, int *fl, int *sl)
{
    int t;

    if ( *r < SMALL_BLOCK )
    {
        *fl = 0;
        *sl = *r / (SMALL_BLOCK / MAX_SLI);
    }
    else
    {
        t = (1 << (fls(*r) - 1 - MAX_LOG2_SLI)) - 1;
        *r = *r + t;
        *fl = fls(*r) - 1;
        *sl = (*r >> (*fl - MAX_LOG2_SLI)) - MAX_SLI;
        *fl -= FLI_OFFSET;
        /*if ((*fl -= FLI_OFFSET) < 0) // FL will be always >0!
         *fl = *sl = 0;
         */
        *r &= ~t;
    }
}

/**
 * Returns indexes (fl, sl) which is used as starting point to search
 * for a block of size r. It also rounds up requested size(r) to the
 * next list.
 */
static inline void MAPPING_INSERT(unsigned long r, int *fl, int *sl)
{
    if ( r < SMALL_BLOCK )
    {
        *fl = 0;
        *sl = r / (SMALL_BLOCK / MAX_SLI);
    }
    else
    {
        *fl = fls(r) - 1;
        *sl = (r >> (*fl - MAX_LOG2_SLI)) - MAX_SLI;
        *fl -= FLI_OFFSET;
    }
}

/**
 * Returns first block from a list that hold blocks larger than or
 * equal to the one pointed by the indexes (fl, sl)
 */
static inline struct bhdr *FIND_SUITABLE_BLOCK(struct xmem_pool *p, int *fl,
                                               int *sl)
{
    u32 tmp = p->sl_bitmap[*fl] & (~0 << *sl);
    struct bhdr *b = NULL;

    if ( tmp )
    {
        *sl = ffs(tmp) - 1;
        b = p->matrix[*fl][*sl];
    }
    else
    {
        *fl = ffs(p->fl_bitmap & (~0 << (*fl + 1))) - 1;
        if ( likely(*fl > 0) )
        {
            *sl = ffs(p->sl_bitmap[*fl]) - 1;
            b = p->matrix[*fl][*sl];
        }
    }

    return b;
}

/**
 * Remove first free block(b) from free list with indexes (fl, sl).
 */
static inline void EXTRACT_BLOCK_HDR(struct bhdr *b, struct xmem_pool *p, int fl,
                                     int sl)
{
    p->matrix[fl][sl] = b->ptr.free_ptr.next;
    if ( p->matrix[fl][sl] )
    {
        p->matrix[fl][sl]->ptr.free_ptr.prev = NULL;
    }
    else
    {
        clear_bit(sl, &p->sl_bitmap[fl]);
        if ( !p->sl_bitmap[fl] )
            clear_bit(fl, &p->fl_bitmap);
    }
    b->ptr.free_ptr = (struct free_ptr) {NULL, NULL};
}

/**
 * Removes block(b) from free list with indexes (fl, sl)
 */
static inline void EXTRACT_BLOCK(struct bhdr *b, struct xmem_pool *p, int fl,
                                 int sl)
{
    if ( b->ptr.free_ptr.next )
        b->ptr.free_ptr.next->ptr.free_ptr.prev =
            b->ptr.free_ptr.prev;
    if ( b->ptr.free_ptr.prev )
        b->ptr.free_ptr.prev->ptr.free_ptr.next =
            b->ptr.free_ptr.next;
    if ( p->matrix[fl][sl] == b )
    {
        p->matrix[fl][sl] = b->ptr.free_ptr.next;
        if ( !p->matrix[fl][sl] )
        {
            clear_bit(sl, &p->sl_bitmap[fl]);
            if ( !p->sl_bitmap[fl] )
                clear_bit (fl, &p->fl_bitmap);
        }
    }
    b->ptr.free_ptr = (struct free_ptr) {NULL, NULL};
}

/**
 * Insert block(b) in free list with indexes (fl, sl)
 */
static inline void INSERT_BLOCK(struct bhdr *b, struct xmem_pool *p, int fl, int sl)
{
    b->ptr.free_ptr = (struct free_ptr) {NULL, p->matrix[fl][sl]};
    if ( p->matrix[fl][sl] )
        p->matrix[fl][sl]->ptr.free_ptr.prev = b;
    p->matrix[fl][sl] = b;
    set_bit(sl, &p->sl_bitmap[fl]);
    set_bit(fl, &p->fl_bitmap);
}

/**
 * Region is a virtually contiguous memory region and Pool is
 * collection of such regions
 */
static inline void ADD_REGION(void *region, unsigned long region_size,
                              struct xmem_pool *pool)
{
    int fl, sl;
    struct bhdr *b, *lb;

    b = (struct bhdr *)(region);
    b->prev_hdr = NULL;
    b->size = ROUNDDOWN_SIZE(region_size - 2 * BHDR_OVERHEAD)
        | FREE_BLOCK | PREV_USED;
    MAPPING_INSERT(b->size & BLOCK_SIZE_MASK, &fl, &sl);
    INSERT_BLOCK(b, pool, fl, sl);
    /* The sentinel block: allows us to know when we're in the last block */
    lb = GET_NEXT_BLOCK(b->ptr.buffer, b->size & BLOCK_SIZE_MASK);
    lb->prev_hdr = b;
    lb->size = 0 | USED_BLOCK | PREV_FREE;
    pool->used_size += BHDR_OVERHEAD; /* only sentinel block is "used" */
    pool->num_regions++;
}

/*
 * TLSF pool-based allocator start.
 */

struct xmem_pool *xmem_pool_create(
    const char *name,
    xmem_pool_get_memory get_mem,
    xmem_pool_put_memory put_mem,
    unsigned long init_size,
    unsigned long max_size,
    unsigned long grow_size)
{
    struct xmem_pool *pool;
    int pool_bytes, pool_order;

    BUG_ON(max_size && (max_size < init_size));

    pool_bytes = ROUNDUP_SIZE(sizeof(*pool));
    pool_order = get_order_from_bytes(pool_bytes);

    pool = (void *)alloc_xenheap_pages(pool_order, 0);
    if ( pool == NULL )
        return NULL;
    memset(pool, 0, pool_bytes);

    /* Round to next page boundary */
    init_size = ROUNDUP_PAGE(init_size);
    max_size = ROUNDUP_PAGE(max_size);
    grow_size = ROUNDUP_PAGE(grow_size);

    /* pool global overhead not included in used size */
    pool->used_size = 0;

    pool->init_size = init_size;
    pool->max_size = max_size;
    pool->grow_size = grow_size;
    pool->get_mem = get_mem;
    pool->put_mem = put_mem;
    strlcpy(pool->name, name, sizeof(pool->name));

    /* always obtain init_region lazily now to ensure it is get_mem'd
     * in the same "context" as all other regions */

    spin_lock_init(&pool->lock);

    spin_lock(&pool_list_lock);
    list_add_tail(&pool->list, &pool_list_head);
    spin_unlock(&pool_list_lock);

    return pool;
}

unsigned long xmem_pool_get_used_size(struct xmem_pool *pool)
{
    return pool->used_size;
}

unsigned long xmem_pool_get_total_size(struct xmem_pool *pool)
{
    unsigned long total;
    total = ROUNDUP_SIZE(sizeof(*pool))
        + pool->init_size
        + (pool->num_regions - 1) * pool->grow_size;
    return total;
}

void xmem_pool_destroy(struct xmem_pool *pool) 
{
    int pool_bytes, pool_order;

    if ( pool == NULL )
        return;

    /* User is destroying without ever allocating from this pool */
    if ( xmem_pool_get_used_size(pool) == BHDR_OVERHEAD )
    {
        ASSERT(!pool->init_region);
        pool->used_size -= BHDR_OVERHEAD;
    }

    /* Check for memory leaks in this pool */
    if ( xmem_pool_get_used_size(pool) )
        printk("memory leak in pool: %s (%p). "
               "%lu bytes still in use.\n",
               pool->name, pool, xmem_pool_get_used_size(pool));

    spin_lock(&pool_list_lock);
    list_del_init(&pool->list);
    spin_unlock(&pool_list_lock);

    pool_bytes = ROUNDUP_SIZE(sizeof(*pool));
    pool_order = get_order_from_bytes(pool_bytes);
    free_xenheap_pages(pool,pool_order);
}

void *xmem_pool_alloc(unsigned long size, struct xmem_pool *pool)
{
    struct bhdr *b, *b2, *next_b, *region;
    int fl, sl;
    unsigned long tmp_size;

    if ( pool->init_region == NULL )
    {
        if ( (region = pool->get_mem(pool->init_size)) == NULL )
            goto out;
        ADD_REGION(region, pool->init_size, pool);
        pool->init_region = region;
    }

    size = (size < MIN_BLOCK_SIZE) ? MIN_BLOCK_SIZE : ROUNDUP_SIZE(size);
    /* Rounding up the requested size and calculating fl and sl */

    spin_lock(&pool->lock);
 retry_find:
    MAPPING_SEARCH(&size, &fl, &sl);

    /* Searching a free block */
    if ( !(b = FIND_SUITABLE_BLOCK(pool, &fl, &sl)) )
    {
        /* Not found */
        if ( size > (pool->grow_size - 2 * BHDR_OVERHEAD) )
            goto out_locked;
        if ( pool->max_size && (pool->init_size +
                                pool->num_regions * pool->grow_size
                                > pool->max_size) )
            goto out_locked;
        spin_unlock(&pool->lock);
        if ( (region = pool->get_mem(pool->grow_size)) == NULL )
            goto out;
        spin_lock(&pool->lock);
        ADD_REGION(region, pool->grow_size, pool);
        goto retry_find;
    }
    EXTRACT_BLOCK_HDR(b, pool, fl, sl);

    /*-- found: */
    next_b = GET_NEXT_BLOCK(b->ptr.buffer, b->size & BLOCK_SIZE_MASK);
    /* Should the block be split? */
    tmp_size = (b->size & BLOCK_SIZE_MASK) - size;
    if ( tmp_size >= sizeof(struct bhdr) )
    {
        tmp_size -= BHDR_OVERHEAD;
        b2 = GET_NEXT_BLOCK(b->ptr.buffer, size);

        b2->size = tmp_size | FREE_BLOCK | PREV_USED;
        b2->prev_hdr = b;

        next_b->prev_hdr = b2;

        MAPPING_INSERT(tmp_size, &fl, &sl);
        INSERT_BLOCK(b2, pool, fl, sl);

        b->size = size | (b->size & PREV_STATE);
    }
    else
    {
        next_b->size &= (~PREV_FREE);
        b->size &= (~FREE_BLOCK); /* Now it's used */
    }

    pool->used_size += (b->size & BLOCK_SIZE_MASK) + BHDR_OVERHEAD;

    spin_unlock(&pool->lock);
    return (void *)b->ptr.buffer;

    /* Failed alloc */
 out_locked:
    spin_unlock(&pool->lock);

 out:
    return NULL;
}

void xmem_pool_free(void *ptr, struct xmem_pool *pool)
{
    struct bhdr *b, *tmp_b;
    int fl = 0, sl = 0;

    if ( unlikely(ptr == NULL) )
        return;

    b = (struct bhdr *)((char *) ptr - BHDR_OVERHEAD);

    spin_lock(&pool->lock);
    b->size |= FREE_BLOCK;
    pool->used_size -= (b->size & BLOCK_SIZE_MASK) + BHDR_OVERHEAD;
    b->ptr.free_ptr = (struct free_ptr) { NULL, NULL};
    tmp_b = GET_NEXT_BLOCK(b->ptr.buffer, b->size & BLOCK_SIZE_MASK);
    if ( tmp_b->size & FREE_BLOCK )
    {
        MAPPING_INSERT(tmp_b->size & BLOCK_SIZE_MASK, &fl, &sl);
        EXTRACT_BLOCK(tmp_b, pool, fl, sl);
        b->size += (tmp_b->size & BLOCK_SIZE_MASK) + BHDR_OVERHEAD;
    }
    if ( b->size & PREV_FREE )
    {
        tmp_b = b->prev_hdr;
        MAPPING_INSERT(tmp_b->size & BLOCK_SIZE_MASK, &fl, &sl);
        EXTRACT_BLOCK(tmp_b, pool, fl, sl);
        tmp_b->size += (b->size & BLOCK_SIZE_MASK) + BHDR_OVERHEAD;
        b = tmp_b;
    }
    tmp_b = GET_NEXT_BLOCK(b->ptr.buffer, b->size & BLOCK_SIZE_MASK);
    tmp_b->prev_hdr = b;

    MAPPING_INSERT(b->size & BLOCK_SIZE_MASK, &fl, &sl);

    if ( (b->prev_hdr == NULL) && ((tmp_b->size & BLOCK_SIZE_MASK) == 0) )
    {
        pool->put_mem(b);
        pool->num_regions--;
        pool->used_size -= BHDR_OVERHEAD; /* sentinel block header */
        goto out;
    }

    INSERT_BLOCK(b, pool, fl, sl);

    tmp_b->size |= PREV_FREE;
    tmp_b->prev_hdr = b;
 out:
    spin_unlock(&pool->lock);
}

int xmem_pool_maxalloc(struct xmem_pool *pool)
{
    return pool->grow_size - (2 * BHDR_OVERHEAD);
}

/*
 * Glue for xmalloc().
 */

static struct xmem_pool *xenpool;

static void *xmalloc_pool_get(unsigned long size)
{
    ASSERT(size == PAGE_SIZE);
    return alloc_xenheap_page();
}

static void xmalloc_pool_put(void *p)
{
    free_xenheap_page(p);
}

static void *xmalloc_whole_pages(unsigned long size)
{
    struct bhdr *b;
    unsigned int i, pageorder = get_order_from_bytes(size + BHDR_OVERHEAD);
    char *p;

    b = alloc_xenheap_pages(pageorder, 0);
    if ( b == NULL )
        return NULL;

    b->size = PAGE_ALIGN(size + BHDR_OVERHEAD);
    for ( p = (char *)b + b->size, i = 0; i < pageorder; ++i )
        if ( (unsigned long)p & (PAGE_SIZE << i) )
        {
            free_xenheap_pages(p, i);
            p += PAGE_SIZE << i;
        }

    return (void *)b->ptr.buffer;
}

static void tlsf_init(void)
{
    INIT_LIST_HEAD(&pool_list_head);
    spin_lock_init(&pool_list_lock);
    xenpool = xmem_pool_create(
        "xmalloc", xmalloc_pool_get, xmalloc_pool_put,
        PAGE_SIZE, 0, PAGE_SIZE);
    BUG_ON(!xenpool);
}

/*
 * xmalloc()
 */

void *_xmalloc(unsigned long size, unsigned long align)
{
    void *p = NULL;
    u32 pad;

    ASSERT(!in_irq());

    ASSERT((align & (align - 1)) == 0);
    if ( align < MEM_ALIGN )
        align = MEM_ALIGN;
    size += align - MEM_ALIGN;

    if ( !xenpool )
        tlsf_init();

    if ( size < PAGE_SIZE )
        p = xmem_pool_alloc(size, xenpool);
    if ( p == NULL )
        p = xmalloc_whole_pages(size);

    /* Add alignment padding. */
    if ( (pad = -(long)p & (align - 1)) != 0 )
    {
        char *q = (char *)p + pad;
        struct bhdr *b = (struct bhdr *)(q - BHDR_OVERHEAD);
        ASSERT(q > (char *)p);
        b->size = pad | 1;
        p = q;
    }

    ASSERT(((unsigned long)p & (align - 1)) == 0);
    return p;
}

void *_xzalloc(unsigned long size, unsigned long align)
{
    void *p = _xmalloc(size, align);

    return p ? memset(p, 0, size) : p;
}

void xfree(void *p)
{
    struct bhdr *b;

    if ( p == NULL )
        return;

    ASSERT(!in_irq());

    /* Strip alignment padding. */
    b = (struct bhdr *)((char *) p - BHDR_OVERHEAD);
    if ( b->size & 1 )
    {
        p = (char *)p - (b->size & ~1u);
        b = (struct bhdr *)((char *)p - BHDR_OVERHEAD);
        ASSERT(!(b->size & 1));
    }

    if ( b->size >= PAGE_SIZE )
    {
        unsigned int i, order = get_order_from_bytes(b->size);

        BUG_ON((unsigned long)b & ((PAGE_SIZE << order) - 1));
        for ( i = 0; ; ++i )
        {
            if ( !(b->size & (PAGE_SIZE << i)) )
                continue;
            b->size -= PAGE_SIZE << i;
            free_xenheap_pages((void *)b + b->size, i);
            if ( i + 1 >= order )
                break;
        }
    }
    else
        xmem_pool_free(p, xenpool);
}