File libxc-sr-save-local_pages.patch of Package xen

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File libxc-sr-save-local_pages.patch of Package xen (Revision 778a304091f73935cdf421049b9d0ba3)

Currently displaying revision 778a304091f73935cdf421049b9d0ba3 , Show latest

From: Olaf Hering <olaf@aepfle.de>
Date: Fri, 23 Oct 2020 12:47:56 +0200
Subject: libxc sr save local_pages

tools/guest: save: move local_pages array

Remove allocation from hotpath, move local_pages array into preallocated space.

Adjust the code to use the src page as is in case of HVM.
In case of PV the page may need to be normalised, use an private memory
area for this purpose.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
---
 tools/libxc/xc_sr_common.h       | 22 ++++++++++++----------
 tools/libxc/xc_sr_save.c         | 25 +++----------------------
 tools/libxc/xc_sr_save_x86_hvm.c |  5 +++--
 tools/libxc/xc_sr_save_x86_pv.c  | 31 +++++++++++++++++++++----------
 4 files changed, 39 insertions(+), 44 deletions(-)

--- xen-4.14.0-testing.orig/tools/libxc/xc_sr_common.h
+++ xen-4.14.0-testing/tools/libxc/xc_sr_common.h
@@ -34,16 +34,12 @@ struct xc_sr_save_ops
      * Optionally transform the contents of a page from being specific to the
      * sending environment, to being generic for the stream.
      *
-     * The page of data at the end of 'page' may be a read-only mapping of a
-     * running guest; it must not be modified.  If no transformation is
-     * required, the callee should leave '*pages' untouched.
+     * The page of data '*src' may be a read-only mapping of a running guest;
+     * it must not be modified. If no transformation is required, the callee
+     * should leave '*src' untouched, and return it via '**ptr'.
      *
-     * If a transformation is required, the callee should allocate themselves
-     * a local page using malloc() and return it via '*page'.
-     *
-     * The caller shall free() '*page' in all cases.  In the case that the
-     * callee encounters an error, it should *NOT* free() the memory it
-     * allocated for '*page'.
+     * If a transformation is required, the callee should provide the
+     * transformed page in a private buffer and return it via '**ptr'.
      *
      * It is valid to fail with EAGAIN if the transformation is not able to be
      * completed at this point.  The page shall be retried later.
@@ -51,7 +47,7 @@ struct xc_sr_save_ops
      * @returns 0 for success, -1 for failure, with errno appropriately set.
      */
     int (*normalise_page)(struct xc_sr_context *ctx, xen_pfn_t type,
-                          void **page);
+                          void *src, unsigned int idx, void **ptr);
 
     /**
      * Set up local environment to save a domain. (Typically querying
@@ -374,6 +370,12 @@ struct xc_sr_context
                 {
                     struct
                     {
+                        /* Used by write_batch for modified pages. */
+                        void *normalised_pages;
+                    } save;
+
+                    struct
+                    {
                         /* State machine for the order of received records. */
                         bool seen_pv_info;
 
--- xen-4.14.0-testing.orig/tools/libxc/xc_sr_save.c
+++ xen-4.14.0-testing/tools/libxc/xc_sr_save.c
@@ -91,11 +91,10 @@ static int write_batch(struct xc_sr_cont
     xen_pfn_t *mfns = ctx->save.m->mfns, *types = ctx->save.m->types;
     void *guest_mapping = NULL;
     void **guest_data = ctx->save.m->guest_data;
-    void **local_pages = NULL;
     int *errors = ctx->save.m->errors, rc = -1;
     unsigned int i, p, nr_pages = 0, nr_pages_mapped = 0;
     unsigned int nr_pfns = ctx->save.nr_batch_pfns;
-    void *page, *orig_page;
+    void *src;
     uint64_t *rec_pfns = ctx->save.m->rec_pfns;
     struct iovec *iov = ctx->save.m->iov; int iovcnt = 0;
     struct xc_sr_rec_page_data_header hdr = { 0 };
@@ -105,16 +104,6 @@ static int write_batch(struct xc_sr_cont
 
     assert(nr_pfns != 0);
 
-    /* Pointers to locally allocated pages.  Need freeing. */
-    local_pages = calloc(nr_pfns, sizeof(*local_pages));
-
-    if ( !local_pages )
-    {
-        ERROR("Unable to allocate arrays for a batch of %u pages",
-              nr_pfns);
-        goto err;
-    }
-
     for ( i = 0; i < nr_pfns; ++i )
     {
         types[i] = mfns[i] = ctx->save.ops.pfn_to_gfn(ctx,
@@ -176,11 +165,8 @@ static int write_batch(struct xc_sr_cont
                 goto err;
             }
 
-            orig_page = page = guest_mapping + (p * PAGE_SIZE);
-            rc = ctx->save.ops.normalise_page(ctx, types[i], &page);
-
-            if ( orig_page != page )
-                local_pages[i] = page;
+            src = guest_mapping + (p * PAGE_SIZE);
+            rc = ctx->save.ops.normalise_page(ctx, types[i], src, i, &guest_data[i]);
 
             if ( rc )
             {
@@ -195,8 +181,6 @@ static int write_batch(struct xc_sr_cont
                 else
                     goto err;
             }
-            else
-                guest_data[i] = page;
 
             rc = -1;
             ++p;
@@ -255,9 +239,6 @@ static int write_batch(struct xc_sr_cont
  err:
     if ( guest_mapping )
         xenforeignmemory_unmap(xch->fmem, guest_mapping, nr_pages_mapped);
-    for ( i = 0; local_pages && i < nr_pfns; ++i )
-        free(local_pages[i]);
-    free(local_pages);
 
     return rc;
 }
--- xen-4.14.0-testing.orig/tools/libxc/xc_sr_save_x86_hvm.c
+++ xen-4.14.0-testing/tools/libxc/xc_sr_save_x86_hvm.c
@@ -129,9 +129,10 @@ static xen_pfn_t x86_hvm_pfn_to_gfn(cons
     return pfn;
 }
 
-static int x86_hvm_normalise_page(struct xc_sr_context *ctx,
-                                  xen_pfn_t type, void **page)
+static int x86_hvm_normalise_page(struct xc_sr_context *ctx, xen_pfn_t type,
+                                  void *src, unsigned int idx, void **ptr)
 {
+    *ptr = src;
     return 0;
 }
 
--- xen-4.14.0-testing.orig/tools/libxc/xc_sr_save_x86_pv.c
+++ xen-4.14.0-testing/tools/libxc/xc_sr_save_x86_pv.c
@@ -999,29 +999,31 @@ static xen_pfn_t x86_pv_pfn_to_gfn(const
  * save_ops function.  Performs pagetable normalisation on appropriate pages.
  */
 static int x86_pv_normalise_page(struct xc_sr_context *ctx, xen_pfn_t type,
-                                 void **page)
+                                  void *src, unsigned int idx, void **ptr)
 {
     xc_interface *xch = ctx->xch;
-    void *local_page;
     int rc;
+    void *dst;
 
     type &= XEN_DOMCTL_PFINFO_LTABTYPE_MASK;
 
     if ( type < XEN_DOMCTL_PFINFO_L1TAB || type > XEN_DOMCTL_PFINFO_L4TAB )
+    {
+        *ptr = src;
         return 0;
+    }
 
-    local_page = malloc(PAGE_SIZE);
-    if ( !local_page )
+    if ( idx >= MAX_BATCH_SIZE )
     {
-        ERROR("Unable to allocate scratch page");
-        rc = -1;
-        goto out;
+        ERROR("idx %u out of range", idx);
+        errno = ERANGE;
+        return -1;
     }
 
-    rc = normalise_pagetable(ctx, *page, local_page, type);
-    *page = local_page;
+    dst = ctx->x86.pv.save.normalised_pages + idx * PAGE_SIZE;
+    rc = normalise_pagetable(ctx, src, dst, type);
+    *ptr = dst;
 
- out:
     return rc;
 }
 
@@ -1031,8 +1033,16 @@ static int x86_pv_normalise_page(struct
  */
 static int x86_pv_setup(struct xc_sr_context *ctx)
 {
+    xc_interface *xch = ctx->xch;
     int rc;
 
+    ctx->x86.pv.save.normalised_pages = malloc(MAX_BATCH_SIZE * PAGE_SIZE);
+    if ( !ctx->x86.pv.save.normalised_pages )
+    {
+        PERROR("Failed to allocate normalised_pages");
+        return -1;
+    }
+
     rc = x86_pv_domain_info(ctx);
     if ( rc )
         return rc;
@@ -1118,6 +1128,7 @@ static int x86_pv_check_vm_state(struct
 
 static int x86_pv_cleanup(struct xc_sr_context *ctx)
 {
+    free(ctx->x86.pv.save.normalised_pages);
     free(ctx->x86.pv.p2m_pfns);
 
     if ( ctx->x86.pv.p2m )

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File libxc-sr-save-local_pages.patch of Package xen (Revision 778a304091f73935cdf421049b9d0ba3)

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