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[Xen-devel] [PATCH] tools/libxc: Drop unused xc_compression_*()



There have been no users of the xc_compression_*() interface since Migration
v2 replaced legacy migration (2016, c/s b15bc4345).

It would need adjusting to fit into migration v2, and can be pulled out of git
history if someone wants to resurrect it in the future.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Ian Jackson <Ian.Jackson@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
---
 tools/libxc/Makefile          |   2 +-
 tools/libxc/include/xenctrl.h |  60 -----
 tools/libxc/xc_compression.c  | 545 ------------------------------------------
 3 files changed, 1 insertion(+), 606 deletions(-)
 delete mode 100644 tools/libxc/xc_compression.c

diff --git a/tools/libxc/Makefile b/tools/libxc/Makefile
index cbc30001f6..6d0af563c0 100644
--- a/tools/libxc/Makefile
+++ b/tools/libxc/Makefile
@@ -63,7 +63,7 @@ GUEST_SRCS-$(CONFIG_X86) += xc_sr_save_x86_pv.c
 GUEST_SRCS-$(CONFIG_X86) += xc_sr_save_x86_hvm.c
 GUEST_SRCS-y += xc_sr_restore.c
 GUEST_SRCS-y += xc_sr_save.c
-GUEST_SRCS-y += xc_offline_page.c xc_compression.c
+GUEST_SRCS-y += xc_offline_page.c
 else
 GUEST_SRCS-y += xc_nomigrate.c
 endif
diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index f4431687b3..983f5ac6b0 100644
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -2315,66 +2315,6 @@ void xc_elf_set_logfile(xc_interface *xch, struct 
elf_binary *elf,
                         int verbose);
 /* Useful for callers who also use libelf. */
 
-/**
- * Checkpoint Compression
- */
-typedef struct compression_ctx comp_ctx;
-comp_ctx *xc_compression_create_context(xc_interface *xch,
-                                       unsigned long p2m_size);
-void xc_compression_free_context(xc_interface *xch, comp_ctx *ctx);
-
-/**
- * Add a page to compression page buffer, to be compressed later.
- *
- * returns 0 if the page was successfully added to the page buffer
- *
- * returns -1 if there is no space in buffer. In this case, the
- *  application should call xc_compression_compress_pages to compress
- *  the buffer (or atleast part of it), thereby freeing some space in
- *  the page buffer.
- *
- * returns -2 if the pfn is out of bounds, where the bound is p2m_size
- *  parameter passed during xc_compression_create_context.
- */
-int xc_compression_add_page(xc_interface *xch, comp_ctx *ctx, char *page,
-                           unsigned long pfn, int israw);
-
-/**
- * Delta compress pages in the compression buffer and inserts the
- * compressed data into the supplied compression buffer compbuf, whose
- * size is compbuf_size.
- * After compression, the pages are copied to the internal LRU cache.
- *
- * This function compresses as many pages as possible into the
- * supplied compression buffer. It maintains an internal iterator to
- * keep track of pages in the input buffer that are yet to be compressed.
- *
- * returns -1 if the compression buffer has run out of space.  
- * returns 1 on success.
- * returns 0 if no more pages are left to be compressed.
- *  When the return value is non-zero, compbuf_len indicates the actual
- *  amount of data present in compbuf (<=compbuf_size).
- */
-int xc_compression_compress_pages(xc_interface *xch, comp_ctx *ctx,
-                                 char *compbuf, unsigned long compbuf_size,
-                                 unsigned long *compbuf_len);
-
-/**
- * Resets the internal page buffer that holds dirty pages before compression.
- * Also resets the iterators.
- */
-void xc_compression_reset_pagebuf(xc_interface *xch, comp_ctx *ctx);
-
-/**
- * Caller must supply the compression buffer (compbuf),
- * its size (compbuf_size) and a reference to index variable (compbuf_pos)
- * that is used internally. Each call pulls out one page from the compressed
- * chunk and copies it to dest.
- */
-int xc_compression_uncompress_page(xc_interface *xch, char *compbuf,
-                                  unsigned long compbuf_size,
-                                  unsigned long *compbuf_pos, char *dest);
-
 /*
  * Execute an image previously loaded with xc_kexec_load().
  *
diff --git a/tools/libxc/xc_compression.c b/tools/libxc/xc_compression.c
deleted file mode 100644
index 89c1114ebb..0000000000
--- a/tools/libxc/xc_compression.c
+++ /dev/null
@@ -1,545 +0,0 @@
-/******************************************************************************
- * xc_compression.c
- *
- * Checkpoint Compression using Page Delta Algorithm.
- * - A LRU cache of recently dirtied guest pages is maintained.
- * - For each dirty guest page in the checkpoint, if a previous version of the
- * page exists in the cache, XOR both pages and send the non-zero sections
- * to the receiver. The cache is then updated with the newer copy of guest 
page.
- * - The receiver will XOR the non-zero sections against its copy of the guest
- * page, thereby bringing the guest page up-to-date with the sender side.
- *
- * Copyright (c) 2011 Shriram Rajagopalan (rshriram@xxxxxxxxx).
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation;
- * version 2.1 of the License.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; If not, see <http://www.gnu.org/licenses/>.
- *
- */
-
-#include <stdio.h>
-#include <stdlib.h>
-#include <unistd.h>
-#include <sys/types.h>
-#include <inttypes.h>
-#include "xc_private.h"
-#include "xenctrl.h"
-#include "xg_save_restore.h"
-#include "xg_private.h"
-#include "xc_dom.h"
-
-/* Page Cache for Delta Compression*/
-#define DELTA_CACHE_SIZE (XC_PAGE_SIZE * 8192)
-
-/* Internal page buffer to hold dirty pages of a checkpoint,
- * to be compressed after the domain is resumed for execution.
- */
-#define PAGE_BUFFER_SIZE (XC_PAGE_SIZE * 8192)
-
-struct cache_page
-{
-    char *page;
-    xen_pfn_t pfn;
-    struct cache_page *next;
-    struct cache_page *prev;
-};
-
-struct compression_ctx
-{
-    /* compression buffer - holds compressed data */
-    char *compbuf;
-    unsigned long compbuf_size;
-    unsigned long compbuf_pos;
-
-    /* Page buffer to hold pages to be compressed */
-    char *inputbuf;
-    /* pfns of pages to be compressed */
-    xen_pfn_t *sendbuf_pfns;
-    unsigned int pfns_len;
-    unsigned int pfns_index;
-
-    /* Compression Cache (LRU) */
-    char *cache_base;
-    struct cache_page **pfn2cache;
-    struct cache_page *cache;
-    struct cache_page *page_list_head;
-    struct cache_page *page_list_tail;
-    unsigned long dom_pfnlist_size;
-};
-
-#define RUNFLAG 0
-#define SKIPFLAG ((char)128)
-#define FLAGMASK SKIPFLAG
-#define LENMASK ((char)127)
-
-/*
- * see xg_save_restore.h for details on the compressed stream format.
- * delta size = 4 bytes.
- * run header = 1 byte (1 bit for runtype, 7bits for run length).
- *  i.e maximum size of a run = 127 * 4 = 508 bytes.
- * Worst case compression: Entire page has changed.
- * In the worst case, the size of the compressed page is
- *  8 runs of 508 bytes + 1 run of 32 bytes + 9 run headers 
- *  = 4105 bytes.
- * We could detect this worst case and send the entire page with a
- * FULL_PAGE marker, reducing the total size to 4097 bytes. The cost
- * of this size reduction is an additional memcpy, on top of two previous
- * memcpy (to the compressed stream and the cache page in the for loop).
- *
- * We might as well sacrifice an extra 8 bytes instead of a memcpy.
- */
-#define WORST_COMP_PAGE_SIZE (XC_PAGE_SIZE + 9)
-
-/*
- * A zero length skip indicates full page.
- */
-#define EMPTY_PAGE 0
-#define FULL_PAGE SKIPFLAG
-#define FULL_PAGE_SIZE (XC_PAGE_SIZE + 1)
-#define MAX_DELTAS (XC_PAGE_SIZE/sizeof(uint32_t))
-
-/*
- * Add a pagetable page or a new page (uncached)
- * if srcpage is a pagetable page, cache_page is null.
- * if srcpage is a page that was not previously in the cache,
- *  cache_page points to a free page slot in the cache where
- *  this new page can be copied to.
- */
-static int add_full_page(comp_ctx *ctx, char *srcpage, char *cache_page)
-{
-    char *dest = (ctx->compbuf + ctx->compbuf_pos);
-
-    if ( (ctx->compbuf_pos + FULL_PAGE_SIZE) > ctx->compbuf_size)
-        return -1;
-
-    if (cache_page)
-        memcpy(cache_page, srcpage, XC_PAGE_SIZE);
-    dest[0] = FULL_PAGE;
-    memcpy(&dest[1], srcpage, XC_PAGE_SIZE);
-    ctx->compbuf_pos += FULL_PAGE_SIZE;
-
-    return FULL_PAGE_SIZE;
-}
-
-static int compress_page(comp_ctx *ctx, char *srcpage, char *cache_page)
-{
-    char *dest = (ctx->compbuf + ctx->compbuf_pos);
-    uint32_t *new, *old;
-
-    int off, runptr = 0;
-    int wascopying = 0, copying = 0, bytes_skipped = 0;
-    int complen = 0, pageoff = 0, runbytes = 0;
-
-    char runlen = 0;
-
-    if ( (ctx->compbuf_pos + WORST_COMP_PAGE_SIZE) > ctx->compbuf_size)
-        return -1;
-
-    /*
-     * There are no alignment issues here since srcpage is
-     * domU's page passed from xc_domain_save and cache_page is
-     * a ptr to cache page (cache is page aligned).
-     */
-    new = (uint32_t*)srcpage;
-    old = (uint32_t*)cache_page;
-
-    for (off = 0; off <= MAX_DELTAS; off++)
-    {
-        /*
-         * At (off == MAX_DELTAS), we are processing the last run
-         * in the page. Since there is no XORing, make wascopying != copying
-         * to satisfy the if-block below.
-         */
-        copying = ((off < MAX_DELTAS) ? (old[off] != new[off]) : !wascopying);
-
-        if (runlen)
-        {
-            /* switching between run types or current run is full */
-            if ( (wascopying != copying) || (runlen == LENMASK) )
-            {
-                runbytes = runlen * sizeof(uint32_t);
-                runlen |= (wascopying ? RUNFLAG : SKIPFLAG);
-                dest[complen++] = runlen;
-
-                if (wascopying) /* RUNFLAG */
-                {
-                    pageoff = runptr * sizeof(uint32_t);
-                    memcpy(dest + complen, srcpage + pageoff, runbytes);
-                    memcpy(cache_page + pageoff, srcpage + pageoff, runbytes);
-                    complen += runbytes;
-                }
-                else /* SKIPFLAG */
-                {
-                    bytes_skipped += runbytes;
-                }
-
-                runlen = 0;
-                runptr = off;
-            }
-        }
-        runlen++;
-        wascopying = copying;
-    }
-
-    /*
-     * Check for empty page.
-     */
-    if (bytes_skipped == XC_PAGE_SIZE)
-    {
-        complen = 1;
-        dest[0] = EMPTY_PAGE;
-    }
-    ctx->compbuf_pos += complen;
-
-    return complen;
-}
-
-static
-char *get_cache_page(comp_ctx *ctx, xen_pfn_t pfn,
-                     int *israw)
-{
-    struct cache_page *item = NULL;
-
-    item = ctx->pfn2cache[pfn];
-
-    if (!item)
-    {
-        *israw = 1;
-
-        /* If the list is full, evict a page from the tail end. */
-        item = ctx->page_list_tail;
-        if (item->pfn != INVALID_PFN)
-            ctx->pfn2cache[item->pfn] = NULL;
-
-        item->pfn = pfn;
-        ctx->pfn2cache[pfn] = item;
-    }
-        
-    /*         if requested item is in cache move to head of list */
-    if (item != ctx->page_list_head)
-    {
-        if (item == ctx->page_list_tail)
-        {
-            /* item at tail of list. */
-            ctx->page_list_tail = item->prev;
-            (ctx->page_list_tail)->next = NULL;
-        }
-        else
-        {
-            /* item in middle of list */
-            item->prev->next = item->next;
-            item->next->prev = item->prev;
-        }
-
-        item->prev = NULL;
-        item->next = ctx->page_list_head;
-        (ctx->page_list_head)->prev = item;
-        ctx->page_list_head = item;
-    }
-
-    return (ctx->page_list_head)->page;
-}
-
-/* Remove pagetable pages from cache and move to tail, as free pages */
-static
-void invalidate_cache_page(comp_ctx *ctx, xen_pfn_t pfn)
-{
-    struct cache_page *item = NULL;
-
-    item = ctx->pfn2cache[pfn];
-    if (item)
-    {
-        if (item != ctx->page_list_tail)
-        {
-            /* item at head of list */
-            if (item == ctx->page_list_head)
-            {
-                ctx->page_list_head = (ctx->page_list_head)->next;
-                (ctx->page_list_head)->prev = NULL;
-            }
-            else /* item in middle of list */
-            {            
-                item->prev->next = item->next;
-                item->next->prev = item->prev;
-            }
-
-            item->next = NULL;
-            item->prev = ctx->page_list_tail;
-            (ctx->page_list_tail)->next = item;
-            ctx->page_list_tail = item;
-        }
-        ctx->pfn2cache[pfn] = NULL;
-        (ctx->page_list_tail)->pfn = INVALID_PFN;
-    }
-}
-
-int xc_compression_add_page(xc_interface *xch, comp_ctx *ctx,
-                            char *page, xen_pfn_t pfn, int israw)
-{
-    if (pfn > ctx->dom_pfnlist_size)
-    {
-        ERROR("Invalid pfn passed into "
-              "xc_compression_add_page %" PRIpfn "\n", pfn);
-        return -2;
-    }
-
-    /* pagetable page */
-    if (israw)
-        invalidate_cache_page(ctx, pfn);
-    ctx->sendbuf_pfns[ctx->pfns_len] = israw ? INVALID_PFN : pfn;
-    memcpy(ctx->inputbuf + ctx->pfns_len * XC_PAGE_SIZE, page, XC_PAGE_SIZE);
-    ctx->pfns_len++;
-
-    /* check if we have run out of space. If so,
-     * we need to synchronously compress the pages and flush them out
-     */
-    if (ctx->pfns_len == NRPAGES(PAGE_BUFFER_SIZE))
-        return -1;
-    return 0;
-}
-
-int xc_compression_compress_pages(xc_interface *xch, comp_ctx *ctx,
-                                  char *compbuf, unsigned long compbuf_size,
-                                  unsigned long *compbuf_len)
-{
-    char *cache_copy = NULL, *current_page = NULL;
-    int israw, rc = 1;
-
-    if (!ctx->pfns_len || (ctx->pfns_index == ctx->pfns_len)) {
-        ctx->pfns_len = ctx->pfns_index = 0;
-        return 0;
-    }
-
-    ctx->compbuf_pos = 0;
-    ctx->compbuf = compbuf;
-    ctx->compbuf_size = compbuf_size;
-
-    for (; ctx->pfns_index < ctx->pfns_len; ctx->pfns_index++)
-    {
-        israw = 0;
-        cache_copy = NULL;
-        current_page = ctx->inputbuf + ctx->pfns_index * XC_PAGE_SIZE;
-
-        if (ctx->sendbuf_pfns[ctx->pfns_index] == INVALID_PFN)
-            israw = 1;
-        else
-            cache_copy = get_cache_page(ctx,
-                                        ctx->sendbuf_pfns[ctx->pfns_index],
-                                        &israw);
-
-        if (israw)
-            rc = (add_full_page(ctx, current_page, cache_copy) >= 0);
-        else
-            rc = (compress_page(ctx, current_page, cache_copy) >= 0);
-
-        if ( !rc )
-        {
-            /* Out of space in outbuf! flush and come back */
-            rc = -1;
-            break;
-        }
-    }
-    if (compbuf_len)
-        *compbuf_len = ctx->compbuf_pos;
-
-    return rc;
-}
-
-inline
-void xc_compression_reset_pagebuf(xc_interface *xch, comp_ctx *ctx)
-{
-    ctx->pfns_index = ctx->pfns_len = 0;
-}
-
-int xc_compression_uncompress_page(xc_interface *xch, char *compbuf,
-                                   unsigned long compbuf_size,
-                                   unsigned long *compbuf_pos, char *destpage)
-{
-    unsigned long pos;
-    unsigned int len = 0, pagepos = 0;
-    char flag;
-
-    pos = *compbuf_pos;
-    if (pos >= compbuf_size)
-    {
-        ERROR("Out of bounds exception in compression buffer (a):"
-              "read ptr:%lu, bufsize = %lu\n",
-              *compbuf_pos, compbuf_size);
-        return -1;
-    }
-
-    switch (compbuf[pos])
-    {
-    case EMPTY_PAGE:
-        pos++;
-        break;
-
-    case FULL_PAGE:
-        {
-            /* Check if the input buffer has 4KB of data */
-            if ((pos + FULL_PAGE_SIZE) > compbuf_size)
-            {
-                ERROR("Out of bounds exception in compression buffer (b):"
-                      "read ptr = %lu, bufsize = %lu\n",
-                      *compbuf_pos, compbuf_size);
-                return -1;
-            }
-            memcpy(destpage, &compbuf[pos + 1], XC_PAGE_SIZE);
-            pos += FULL_PAGE_SIZE;
-        }
-        break;
-
-    default: /* Normal page with one or more runs */
-        {
-            do
-            {
-                flag = compbuf[pos] & FLAGMASK;
-                len = (compbuf[pos] & LENMASK) * sizeof(uint32_t);
-                /* Sanity Check: Zero-length runs are allowed only for
-                 * FULL_PAGE and EMPTY_PAGE.
-                 */
-                if (!len)
-                {
-                    ERROR("Zero length run encountered for normal page: "
-                          "buffer (d):read ptr = %lu, flag = %u, "
-                          "bufsize = %lu, pagepos = %u\n",
-                          pos, (unsigned int)flag, compbuf_size, pagepos);
-                    return -1;
-                }
-
-                pos++;
-                if (flag == RUNFLAG)
-                {
-                    /* Check if the input buffer has len bytes of data
-                     * and whether it would fit in the destination page.
-                     */
-                    if (((pos + len) > compbuf_size)
-                        || ((pagepos + len) > XC_PAGE_SIZE))
-                    {
-                        ERROR("Out of bounds exception in compression "
-                              "buffer (c):read ptr = %lu, runlen = %u, "
-                              "bufsize = %lu, pagepos = %u\n",
-                              pos, len, compbuf_size, pagepos);
-                        return -1;
-                    }
-                    memcpy(&destpage[pagepos], &compbuf[pos], len);
-                    pos += len;
-                }
-                pagepos += len;
-            } while ((pagepos < XC_PAGE_SIZE) && (pos < compbuf_size));
-
-            /* Make sure we have copied/skipped 4KB worth of data */
-            if (pagepos != XC_PAGE_SIZE)
-            {
-                ERROR("Invalid data in compression buffer:"
-                      "read ptr = %lu, bufsize = %lu, pagepos = %u\n",
-                      pos, compbuf_size, pagepos);
-                return -1;
-            }
-        }
-    }
-    *compbuf_pos = pos;
-    return 0;
-}
-
-void xc_compression_free_context(xc_interface *xch, comp_ctx *ctx)
-{
-    if (!ctx) return;
-
-    free(ctx->inputbuf);
-    free(ctx->sendbuf_pfns);
-    free(ctx->cache_base);
-    free(ctx->pfn2cache);
-    free(ctx->cache);
-    free(ctx);
-}
-
-comp_ctx *xc_compression_create_context(xc_interface *xch,
-                                        unsigned long p2m_size)
-{
-    unsigned long i;
-    comp_ctx *ctx = NULL;
-    unsigned long num_cache_pages = DELTA_CACHE_SIZE/XC_PAGE_SIZE;
-
-    ctx = (comp_ctx *)malloc(sizeof(comp_ctx));
-    if (!ctx)
-    {
-        ERROR("Failed to allocate compression_ctx\n");
-        goto error;
-    }
-    memset(ctx, 0, sizeof(comp_ctx));
-
-    ctx->inputbuf = xc_memalign(xch, XC_PAGE_SIZE, PAGE_BUFFER_SIZE);
-    if (!ctx->inputbuf)
-    {
-        ERROR("Failed to allocate page buffer\n");
-        goto error;
-    }
-
-    ctx->cache_base = xc_memalign(xch, XC_PAGE_SIZE, DELTA_CACHE_SIZE);
-    if (!ctx->cache_base)
-    {
-        ERROR("Failed to allocate delta cache\n");
-        goto error;
-    }
-
-    ctx->sendbuf_pfns = malloc(NRPAGES(PAGE_BUFFER_SIZE) *
-                               sizeof(xen_pfn_t));
-    if (!ctx->sendbuf_pfns)
-    {
-        ERROR("Could not alloc sendbuf_pfns\n");
-        goto error;
-    }
-    memset(ctx->sendbuf_pfns, -1,
-           NRPAGES(PAGE_BUFFER_SIZE) * sizeof(xen_pfn_t));
-
-    ctx->pfn2cache = calloc(p2m_size, sizeof(struct cache_page *));
-    if (!ctx->pfn2cache)
-    {
-        ERROR("Could not alloc pfn2cache map\n");
-        goto error;
-    }
-
-    ctx->cache = malloc(num_cache_pages * sizeof(struct cache_page));
-    if (!ctx->cache)
-    {
-        ERROR("Could not alloc compression cache\n");
-        goto error;
-    }
-
-    for (i = 0; i < num_cache_pages; i++)
-    {
-        ctx->cache[i].pfn = INVALID_PFN;
-        ctx->cache[i].page = ctx->cache_base + i * XC_PAGE_SIZE;
-        ctx->cache[i].prev = (i == 0) ? NULL : &(ctx->cache[i - 1]);
-        ctx->cache[i].next = ((i+1) == num_cache_pages)? NULL :
-            &(ctx->cache[i + 1]);
-    }
-    ctx->page_list_head = &(ctx->cache[0]);
-    ctx->page_list_tail = &(ctx->cache[num_cache_pages -1]);
-    ctx->dom_pfnlist_size = p2m_size;
-
-    return ctx;
-error:
-    xc_compression_free_context(xch, ctx);
-    return NULL;
-}
-
-/*
- * Local variables:
- * mode: C
- * c-file-style: "BSD"
- * c-basic-offset: 4
- * tab-width: 4
- * indent-tabs-mode: nil
- * End:
- */
-- 
2.11.0


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