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xen/libxc-sr-save-local_pages.patch

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From: Olaf Hering <olaf@aepfle.de>
Date: Fri, 23 Oct 2020 12:47:56 +0200
Subject: libxc sr save local_pages
tools: save: preallocate local_pages array
Remove repeated allocation from migration loop. There will never be
more than MAX_BATCH_SIZE pages to process in a batch.
Allocate the space once.
Adjust the code to use the unmodified src page in case of HVM.
In case of PV the page may need to be normalised, use a private memory
area for this purpose.
Signed-off-by: Olaf Hering <olaf@aepfle.de>
---
tools/libs/guest/xg_sr_common.h | 22 ++++++++++---------
tools/libs/guest/xg_sr_save.c | 26 ++++------------------
tools/libs/guest/xg_sr_save_x86_hvm.c | 5 +++--
tools/libs/guest/xg_sr_save_x86_pv.c | 31 ++++++++++++++++++---------
4 files changed, 40 insertions(+), 44 deletions(-)
--- a/tools/libs/guest/xg_sr_common.h
+++ b/tools/libs/guest/xg_sr_common.h
@@ -33,16 +33,12 @@ 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.
@@ -50,7 +46,7 @@ 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
@@ -359,6 +355,12 @@ 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;
--- a/tools/libs/guest/xg_sr_save.c
+++ b/tools/libs/guest/xg_sr_save.c
@@ -89,11 +89,10 @@ static int write_batch(struct xc_sr_cont
{
xc_interface *xch = ctx->xch;
void *guest_mapping = NULL;
- void **local_pages = NULL;
int 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;
int iovcnt = 0;
struct xc_sr_rec_page_data_header hdr = { 0 };
struct xc_sr_record rec = {
@@ -102,16 +101,6 @@ 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 )
{
ctx->save.types[i] = ctx->save.mfns[i] = ctx->save.ops.pfn_to_gfn(ctx,
@@ -175,11 +164,9 @@ 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, ctx->save.types[i], &page);
-
- if ( orig_page != page )
- local_pages[i] = page;
+ src = guest_mapping + (p * PAGE_SIZE);
+ rc = ctx->save.ops.normalise_page(ctx, ctx->save.types[i], src, i,
+ &ctx->save.guest_data[i]);
if ( rc )
{
@@ -194,8 +181,6 @@ static int write_batch(struct xc_sr_cont
else
goto err;
}
- else
- ctx->save.guest_data[i] = page;
rc = -1;
++p;
@@ -256,9 +241,6 @@ 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;
}
--- a/tools/libs/guest/xg_sr_save_x86_hvm.c
+++ b/tools/libs/guest/xg_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;
}
--- a/tools/libs/guest/xg_sr_save_x86_pv.c
+++ b/tools/libs/guest/xg_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;
+ void *dst;
int rc;
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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