libxc: Handle failed xc_get_hvm_param in domain save

The domain save code will read an HVM param, and if it's not zero,
make an entry for it.  However, if the hypercall fails for any reason,
the data may not be written, and the value for the previous parameter
may be written in the save file as the parameter that failed.

Initialize the value to zero before each hypercall, so that in case of
a failure, no value will be written.

Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

diff --git a/tools/libxc/xc_domain_save.c b/tools/libxc/xc_domain_save.c
index 22bab3c858cbda739ea8c352a1f61a1e8d77be27..fa270f51f6dbc095bc909b0569b48eb83e8e3ab4 100644 (file)
--- a/tools/libxc/xc_domain_save.c
+++ b/tools/libxc/xc_domain_save.c
@@ -1597,6 +1597,7 @@ int xc_domain_save(xc_interface *xch, int io_fd, uint32_t dom, uint32_t max_iter
         } chunk = { 0, };
 
         chunk.id = XC_SAVE_ID_HVM_IDENT_PT;
+        chunk.data = 0;
         xc_get_hvm_param(xch, dom, HVM_PARAM_IDENT_PT,
                          (unsigned long *)&chunk.data);
 
@@ -1608,6 +1609,7 @@ int xc_domain_save(xc_interface *xch, int io_fd, uint32_t dom, uint32_t max_iter
         }
 
         chunk.id = XC_SAVE_ID_HVM_VM86_TSS;
+        chunk.data = 0;
         xc_get_hvm_param(xch, dom, HVM_PARAM_VM86_TSS,
                          (unsigned long *)&chunk.data);
 
@@ -1619,6 +1621,7 @@ int xc_domain_save(xc_interface *xch, int io_fd, uint32_t dom, uint32_t max_iter
         }
 
         chunk.id = XC_SAVE_ID_HVM_CONSOLE_PFN;
+        chunk.data = 0;
         xc_get_hvm_param(xch, dom, HVM_PARAM_CONSOLE_PFN,
                          (unsigned long *)&chunk.data);
 
@@ -1630,6 +1633,7 @@ int xc_domain_save(xc_interface *xch, int io_fd, uint32_t dom, uint32_t max_iter
         }
 
         chunk.id = XC_SAVE_ID_HVM_ACPI_IOPORTS_LOCATION;
+        chunk.data = 0;
         xc_get_hvm_param(xch, dom, HVM_PARAM_ACPI_IOPORTS_LOCATION,
                          (unsigned long *)&chunk.data);