[PATCH v5 5/5] tools/libxc: make use of domain context SHARED_INFO record...

[Paul Durrant <paul@xen.org>]

... in the save/restore code.

This patch replaces direct mapping of the shared_info_frame (retrieved
using XEN_DOMCTL_getdomaininfo) with save/load of the domain context
SHARED_INFO record.

No modifications are made to the definition of the migration stream at
this point. Subsequent patches will define a record in the libxc domain
image format for passing domain context and convert the save/restore code
to use that.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
---
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Wei Liu <wl@xen.org>

NOTE: Ian requested ack from Andrew

v5:
 - Added BUILD_BUG_ON() in write_shared_info() to ensure copied data is not
   bigger than the record buffer

v4:
 - write_shared_info() now needs to allocate the record data since the
   shared info buffer is smaller than PAGE_SIZE

v3:
 - Moved basic get/set domain context functions to common code

v2:
 - Re-based (now making use of DOMAIN_SAVE_FLAG_IGNORE)
---
 tools/libxc/xc_sr_common.c         | 67 +++++++++++++++++++++++++++
 tools/libxc/xc_sr_common.h         | 11 ++++-
 tools/libxc/xc_sr_common_x86_pv.c  | 74 ++++++++++++++++++++++++++++++
 tools/libxc/xc_sr_common_x86_pv.h  |  3 ++
 tools/libxc/xc_sr_restore_x86_pv.c | 26 ++++-------
 tools/libxc/xc_sr_save_x86_pv.c    | 44 ++++++++----------
 tools/libxc/xg_save_restore.h      |  1 +
 7 files changed, 182 insertions(+), 44 deletions(-)

diff --git a/tools/libxc/xc_sr_common.c b/tools/libxc/xc_sr_common.c
index dd9a11b4b5..1acb3765aa 100644
--- a/tools/libxc/xc_sr_common.c
+++ b/tools/libxc/xc_sr_common.c
@@ -138,6 +138,73 @@ int read_record(struct xc_sr_context *ctx, int fd, struct xc_sr_record *rec)
     return 0;
 };
 
+int get_domain_context(struct xc_sr_context *ctx)
+{
+    xc_interface *xch = ctx->xch;
+    size_t len = 0;
+    int rc;
+
+    if ( ctx->domain_context.buffer )
+    {
+        ERROR("Domain context already present");
+        return -1;
+    }
+
+    rc = xc_domain_getcontext(xch, ctx->domid, NULL, &len);
+    if ( rc < 0 )
+    {
+        PERROR("Unable to get size of domain context");
+        return -1;
+    }
+
+    ctx->domain_context.buffer = malloc(len);
+    if ( !ctx->domain_context.buffer )
+    {
+        PERROR("Unable to allocate memory for domain context");
+        return -1;
+    }
+
+    rc = xc_domain_getcontext(xch, ctx->domid, ctx->domain_context.buffer,
+                              &len);
+    if ( rc < 0 )
+    {
+        PERROR("Unable to get domain context");
+        return -1;
+    }
+
+    ctx->domain_context.len = len;
+
+    return 0;
+}
+
+int set_domain_context(struct xc_sr_context *ctx)
+{
+    xc_interface *xch = ctx->xch;
+    int rc;
+
+    if ( !ctx->domain_context.buffer )
+    {
+        ERROR("Domain context not present");
+        return -1;
+    }
+
+    rc = xc_domain_setcontext(xch, ctx->domid, ctx->domain_context.buffer,
+                              ctx->domain_context.len);
+
+    if ( rc < 0 )
+    {
+        PERROR("Unable to set domain context");
+        return -1;
+    }
+
+    return 0;
+}
+
+void common_cleanup(struct xc_sr_context *ctx)
+{
+    free(ctx->domain_context.buffer);
+}
+
 static void __attribute__((unused)) build_assertions(void)
 {
     BUILD_BUG_ON(sizeof(struct xc_sr_ihdr) != 24);
diff --git a/tools/libxc/xc_sr_common.h b/tools/libxc/xc_sr_common.h
index 5dd51ccb15..0d61978b08 100644
--- a/tools/libxc/xc_sr_common.h
+++ b/tools/libxc/xc_sr_common.h
@@ -208,6 +208,11 @@ struct xc_sr_context
 
     xc_dominfo_t dominfo;
 
+    struct {
+        void *buffer;
+        unsigned int len;
+    } domain_context;
+
     union /* Common save or restore data. */
     {
         struct /* Save data. */
@@ -314,7 +319,7 @@ struct xc_sr_context
                 /* The guest pfns containing the p2m leaves */
                 xen_pfn_t *p2m_pfns;
 
-                /* Read-only mapping of guests shared info page */
+                /* Pointer to shared_info (located in context buffer) */
                 shared_info_any_t *shinfo;
 
                 /* p2m generation count for verifying validity of local p2m. */
@@ -425,6 +430,10 @@ int read_record(struct xc_sr_context *ctx, int fd, struct xc_sr_record *rec);
 int populate_pfns(struct xc_sr_context *ctx, unsigned int count,
                   const xen_pfn_t *original_pfns, const uint32_t *types);
 
+int get_domain_context(struct xc_sr_context *ctx);
+int set_domain_context(struct xc_sr_context *ctx);
+void common_cleanup(struct xc_sr_context *ctx);
+
 #endif
 /*
  * Local variables:
diff --git a/tools/libxc/xc_sr_common_x86_pv.c b/tools/libxc/xc_sr_common_x86_pv.c
index d3d425cb82..69d9b142b8 100644
--- a/tools/libxc/xc_sr_common_x86_pv.c
+++ b/tools/libxc/xc_sr_common_x86_pv.c
@@ -182,6 +182,80 @@ int x86_pv_map_m2p(struct xc_sr_context *ctx)
     return rc;
 }
 
+int x86_pv_get_shinfo(struct xc_sr_context *ctx)
+{
+    xc_interface *xch = ctx->xch;
+    unsigned int off = 0;
+    int rc;
+
+#define GET_PTR(_x)                                                         \
+    do {                                                                    \
+        if ( ctx->domain_context.len - off < sizeof(*(_x)) )                \
+        {                                                                   \
+            ERROR("Need another %lu bytes of context, only %u available\n", \
+                  sizeof(*(_x)), ctx->domain_context.len - off);            \
+            return -1;                                                      \
+        }                                                                   \
+        (_x) = ctx->domain_context.buffer + off;                            \
+    } while (false);
+
+    rc = get_domain_context(ctx);
+    if ( rc )
+        return rc;
+
+    for ( ; ; )
+    {
+        struct domain_save_descriptor *desc;
+
+        GET_PTR(desc);
+
+        off += sizeof(*desc);
+
+        switch (desc->typecode)
+        {
+        case DOMAIN_SAVE_CODE(SHARED_INFO):
+        {
+            DOMAIN_SAVE_TYPE(SHARED_INFO) *s;
+
+            GET_PTR(s);
+
+            ctx->x86.pv.shinfo = (shared_info_any_t *)s->buffer;
+            break;
+        }
+        default:
+            break;
+        }
+
+        if ( desc->typecode == DOMAIN_SAVE_CODE(END) )
+            break;
+
+        off += desc->length;
+    }
+
+    if ( !ctx->x86.pv.shinfo )
+    {
+        ERROR("Failed to get SHARED_INFO\n");
+        return -1;
+    }
+
+    return 0;
+
+#undef GET_PTR
+}
+
+int x86_pv_set_shinfo(struct xc_sr_context *ctx)
+{
+    xc_interface *xch = ctx->xch;
+
+    if ( !ctx->x86.pv.shinfo )
+    {
+        ERROR("SHARED_INFO buffer not present\n");
+        return -1;
+    }
+
+    return set_domain_context(ctx);
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/tools/libxc/xc_sr_common_x86_pv.h b/tools/libxc/xc_sr_common_x86_pv.h
index 2ed03309af..01442f48fb 100644
--- a/tools/libxc/xc_sr_common_x86_pv.h
+++ b/tools/libxc/xc_sr_common_x86_pv.h
@@ -97,6 +97,9 @@ int x86_pv_domain_info(struct xc_sr_context *ctx);
  */
 int x86_pv_map_m2p(struct xc_sr_context *ctx);
 
+int x86_pv_get_shinfo(struct xc_sr_context *ctx);
+int x86_pv_set_shinfo(struct xc_sr_context *ctx);
+
 #endif
 /*
  * Local variables:
diff --git a/tools/libxc/xc_sr_restore_x86_pv.c b/tools/libxc/xc_sr_restore_x86_pv.c
index 904ccc462a..21982a38ad 100644
--- a/tools/libxc/xc_sr_restore_x86_pv.c
+++ b/tools/libxc/xc_sr_restore_x86_pv.c
@@ -865,7 +865,7 @@ static int handle_shared_info(struct xc_sr_context *ctx,
     xc_interface *xch = ctx->xch;
     unsigned int i;
     int rc = -1;
-    shared_info_any_t *guest_shinfo = NULL;
+    shared_info_any_t *guest_shinfo;
     const shared_info_any_t *old_shinfo = rec->data;
 
     if ( !ctx->x86.pv.restore.seen_pv_info )
@@ -878,18 +878,14 @@ static int handle_shared_info(struct xc_sr_context *ctx,
     {
         ERROR("X86_PV_SHARED_INFO record wrong size: length %u"
               ", expected 4096", rec->length);
-        goto err;
+        return -1;
     }
 
-    guest_shinfo = xc_map_foreign_range(
-        xch, ctx->domid, PAGE_SIZE, PROT_READ | PROT_WRITE,
-        ctx->dominfo.shared_info_frame);
-    if ( !guest_shinfo )
-    {
-        PERROR("Failed to map Shared Info at mfn %#lx",
-               ctx->dominfo.shared_info_frame);
-        goto err;
-    }
+    rc = x86_pv_get_shinfo(ctx);
+    if ( rc )
+        return rc;
+
+    guest_shinfo = ctx->x86.pv.shinfo;
 
     MEMCPY_FIELD(guest_shinfo, old_shinfo, vcpu_info, ctx->x86.pv.width);
     MEMCPY_FIELD(guest_shinfo, old_shinfo, arch, ctx->x86.pv.width);
@@ -904,13 +900,7 @@ static int handle_shared_info(struct xc_sr_context *ctx,
 
     MEMSET_ARRAY_FIELD(guest_shinfo, evtchn_mask, 0xff, ctx->x86.pv.width);
 
-    rc = 0;
-
- err:
-    if ( guest_shinfo )
-        munmap(guest_shinfo, PAGE_SIZE);
-
-    return rc;
+    return x86_pv_set_shinfo(ctx);
 }
 
 /* restore_ops function. */
diff --git a/tools/libxc/xc_sr_save_x86_pv.c b/tools/libxc/xc_sr_save_x86_pv.c
index f3ccf5bb4b..fdd172b639 100644
--- a/tools/libxc/xc_sr_save_x86_pv.c
+++ b/tools/libxc/xc_sr_save_x86_pv.c
@@ -9,25 +9,6 @@ static inline bool is_canonical_address(xen_vaddr_t vaddr)
     return ((int64_t)vaddr >> 47) == ((int64_t)vaddr >> 63);
 }
 
-/*
- * Maps the guests shared info page.
- */
-static int map_shinfo(struct xc_sr_context *ctx)
-{
-    xc_interface *xch = ctx->xch;
-
-    ctx->x86.pv.shinfo = xc_map_foreign_range(
-        xch, ctx->domid, PAGE_SIZE, PROT_READ, ctx->dominfo.shared_info_frame);
-    if ( !ctx->x86.pv.shinfo )
-    {
-        PERROR("Failed to map shared info frame at mfn %#lx",
-               ctx->dominfo.shared_info_frame);
-        return -1;
-    }
-
-    return 0;
-}
-
 /*
  * Copy a list of mfns from a guest, accounting for differences between guest
  * and toolstack width.  Can fail if truncation would occur.
@@ -854,13 +835,27 @@ static int write_x86_pv_p2m_frames(struct xc_sr_context *ctx)
  */
 static int write_shared_info(struct xc_sr_context *ctx)
 {
+    xc_interface *xch = ctx->xch;
     struct xc_sr_record rec = {
         .type = REC_TYPE_SHARED_INFO,
         .length = PAGE_SIZE,
-        .data = ctx->x86.pv.shinfo,
     };
+    int rc;
 
-    return write_record(ctx, &rec);
+    if ( !(rec.data = calloc(1, PAGE_SIZE)) )
+    {
+        ERROR("Cannot allocate buffer for SHARED_INFO data");
+        return -1;
+    }
+
+    BUILD_BUG_ON(sizeof(*ctx->x86.pv.shinfo) > PAGE_SIZE);
+    memcpy(rec.data, ctx->x86.pv.shinfo, sizeof(*ctx->x86.pv.shinfo));
+
+    rc = write_record(ctx, &rec);
+
+    free(rec.data);
+
+    return rc;
 }
 
 /*
@@ -1041,7 +1036,7 @@ static int x86_pv_setup(struct xc_sr_context *ctx)
     if ( rc )
         return rc;
 
-    rc = map_shinfo(ctx);
+    rc = x86_pv_get_shinfo(ctx);
     if ( rc )
         return rc;
 
@@ -1112,12 +1107,11 @@ static int x86_pv_cleanup(struct xc_sr_context *ctx)
     if ( ctx->x86.pv.p2m )
         munmap(ctx->x86.pv.p2m, ctx->x86.pv.p2m_frames * PAGE_SIZE);
 
-    if ( ctx->x86.pv.shinfo )
-        munmap(ctx->x86.pv.shinfo, PAGE_SIZE);
-
     if ( ctx->x86.pv.m2p )
         munmap(ctx->x86.pv.m2p, ctx->x86.pv.nr_m2p_frames * PAGE_SIZE);
 
+    common_cleanup(ctx);
+
     return 0;
 }
 
diff --git a/tools/libxc/xg_save_restore.h b/tools/libxc/xg_save_restore.h
index 303081df0d..296b523963 100644
--- a/tools/libxc/xg_save_restore.h
+++ b/tools/libxc/xg_save_restore.h
@@ -19,6 +19,7 @@
 
 #include <xen/foreign/x86_32.h>
 #include <xen/foreign/x86_64.h>
+#include <xen/save.h>
 
 /*
 ** We process save/restore/migrate in batches of pages; the below
-- 
2.20.1