[xen staging] tools/libs/guest: fix save and restore of pv domains after 32-bit de-support

[patchbot@xxxxxxx]

commit d21121685fac829c988e432407fb0e4ef9b19331
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Mon Jun 7 15:00:05 2021 +0200
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Mon Jun 7 15:43:35 2021 +0100

    tools/libs/guest: fix save and restore of pv domains after 32-bit de-support
    
    After 32-bit PV-guests have been security de-supported when not running
    under PV-shim, the hypervisor will no longer be configured to support
    those domains per default when not being built as PV-shim.
    
    Unfortunately libxenguest will fail saving or restoring a PV domain
    due to this restriction, as it is trying to get the compat MFN list
    even for 64 bit guests.
    
    Fix that by obtaining the compat MFN list only for 32-bit PV guests.
    
    Fixes: 1a0f2fe2297d122a08fe ("SUPPORT.md: Un-shimmed 32-bit PV guests are 
no longer supported")
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 tools/libs/guest/xg_sr_common.h        |  2 +-
 tools/libs/guest/xg_sr_common_x86_pv.c | 13 ++++++++-----
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/tools/libs/guest/xg_sr_common.h b/tools/libs/guest/xg_sr_common.h
index cc3ad1c394..e2994e18ac 100644
--- a/tools/libs/guest/xg_sr_common.h
+++ b/tools/libs/guest/xg_sr_common.h
@@ -325,7 +325,7 @@ struct xc_sr_context
                 xen_pfn_t max_mfn;
                 /* Read-only machine to phys map */
                 xen_pfn_t *m2p;
-                /* first mfn of the compat m2p (Only needed for 32bit PV 
guests) */
+                /* first mfn of the compat m2p (Only set for 32bit PV guests) 
*/
                 xen_pfn_t compat_m2p_mfn0;
                 /* Number of m2p frames mapped */
                 unsigned long nr_m2p_frames;
diff --git a/tools/libs/guest/xg_sr_common_x86_pv.c 
b/tools/libs/guest/xg_sr_common_x86_pv.c
index cd33406aab..c0acf00f90 100644
--- a/tools/libs/guest/xg_sr_common_x86_pv.c
+++ b/tools/libs/guest/xg_sr_common_x86_pv.c
@@ -149,12 +149,13 @@ int x86_pv_map_m2p(struct xc_sr_context *ctx)
 
     ctx->x86.pv.nr_m2p_frames = (M2P_CHUNK_SIZE >> PAGE_SHIFT) * m2p_chunks;
 
+    if ( ctx->x86.pv.levels == 3 )
+    {
 #ifdef __i386__
-    /* 32 bit toolstacks automatically get the compat m2p */
-    ctx->x86.pv.compat_m2p_mfn0 = entries[0].mfn;
+        /* 32 bit toolstacks automatically get the compat m2p */
+        ctx->x86.pv.compat_m2p_mfn0 = entries[0].mfn;
 #else
-    /* 64 bit toolstacks need to ask Xen specially for it */
-    {
+        /* 64 bit toolstacks need to ask Xen specially for it */
         struct xen_machphys_mfn_list xmml = {
             .max_extents = 1,
             .extent_start = { &ctx->x86.pv.compat_m2p_mfn0 },
@@ -168,8 +169,10 @@ int x86_pv_map_m2p(struct xc_sr_context *ctx)
             rc = -1;
             goto err;
         }
-    }
 #endif
+    }
+    else
+        ctx->x86.pv.compat_m2p_mfn0 = INVALID_MFN;
 
     /* All Done */
     rc = 0;
--
generated by git-patchbot for /home/xen/git/xen.git#staging