libxc: document save/restore protocol

Reverse engineered from the code, likely contains inaccuracies but I
think provides a base to work from.

Add symbolic names for the minus-flags.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>

1 files changed, 8 insertions, 8 deletions

diff --git a/tools/libxc/xc_domain_restore.c b/tools/libxc/xc_domain_restore.c
index 6541021de1..0d326d4a27 100644
--- a/tools/libxc/xc_domain_restore.c
+++ b/tools/libxc/xc_domain_restore.c
@@ -683,11 +683,11 @@ static int pagebuf_get_one(xc_interface *xch, struct restore_ctx *ctx,
     if (!count) {
         // DPRINTF("Last batch read\n");
         return 0;
-    } else if (count == -1) {
+    } else if (count == XC_SAVE_ID_ENABLE_VERIFY_MODE) {
         DPRINTF("Entering page verify mode\n");
         buf->verify = 1;
         return pagebuf_get_one(xch, ctx, buf, fd, dom);
-    } else if (count == -2) {
+    } else if (count == XC_SAVE_ID_VCPU_INFO) {
         buf->new_ctxt_format = 1;
         if ( RDEXACT(fd, &buf->max_vcpu_id, sizeof(buf->max_vcpu_id)) ||
              buf->max_vcpu_id >= 64 || RDEXACT(fd, &buf->vcpumap,
@@ -697,7 +697,7 @@ static int pagebuf_get_one(xc_interface *xch, struct restore_ctx *ctx,
         }
         // DPRINTF("Max VCPU ID: %d, vcpumap: %llx\n", buf->max_vcpu_id, buf->vcpumap);
         return pagebuf_get_one(xch, ctx, buf, fd, dom);
-    } else if (count == -3) {
+    } else if (count == XC_SAVE_ID_HVM_IDENT_PT) {
         /* Skip padding 4 bytes then read the EPT identity PT location. */
         if ( RDEXACT(fd, &buf->identpt, sizeof(uint32_t)) ||
              RDEXACT(fd, &buf->identpt, sizeof(uint64_t)) )
@@ -707,7 +707,7 @@ static int pagebuf_get_one(xc_interface *xch, struct restore_ctx *ctx,
         }
         // DPRINTF("EPT identity map address: %llx\n", buf->identpt);
         return pagebuf_get_one(xch, ctx, buf, fd, dom);
-    } else if ( count == -4 )  {
+    } else if ( count == XC_SAVE_ID_HVM_VM86_TSS )  {
         /* Skip padding 4 bytes then read the vm86 TSS location. */
         if ( RDEXACT(fd, &buf->vm86_tss, sizeof(uint32_t)) ||
              RDEXACT(fd, &buf->vm86_tss, sizeof(uint64_t)) )
@@ -717,7 +717,7 @@ static int pagebuf_get_one(xc_interface *xch, struct restore_ctx *ctx,
         }
         // DPRINTF("VM86 TSS location: %llx\n", buf->vm86_tss);
         return pagebuf_get_one(xch, ctx, buf, fd, dom);
-    } else if ( count == -5 ) {
+    } else if ( count == XC_SAVE_ID_TMEM ) {
         DPRINTF("xc_domain_restore start tmem\n");
         if ( xc_tmem_restore(xch, dom, fd) ) {
             PERROR("error reading/restoring tmem");
@@ -725,13 +725,13 @@ static int pagebuf_get_one(xc_interface *xch, struct restore_ctx *ctx,
         }
         return pagebuf_get_one(xch, ctx, buf, fd, dom);
     }
-    else if ( count == -6 ) {
+    else if ( count == XC_SAVE_ID_TMEM_EXTRA ) {
         if ( xc_tmem_restore_extra(xch, dom, fd) ) {
             PERROR("error reading/restoring tmem extra");
             return -1;
         }
         return pagebuf_get_one(xch, ctx, buf, fd, dom);
-    } else if ( count == -7 ) {
+    } else if ( count == XC_SAVE_ID_TSC_INFO ) {
         uint32_t tsc_mode, khz, incarn;
         uint64_t nsec;
         if ( RDEXACT(fd, &tsc_mode, sizeof(uint32_t)) ||
@@ -743,7 +743,7 @@ static int pagebuf_get_one(xc_interface *xch, struct restore_ctx *ctx,
             return -1;
         }
         return pagebuf_get_one(xch, ctx, buf, fd, dom);
-    } else if (count == -8 ) {
+    } else if (count == XC_SAVE_ID_HVM_CONSOLE_PFN ) {
         /* Skip padding 4 bytes then read the console pfn location. */
         if ( RDEXACT(fd, &buf->console_pfn, sizeof(uint32_t)) ||
              RDEXACT(fd, &buf->console_pfn, sizeof(uint64_t)) )