path: root/xen-common.c
diff options
authorIan Campbell <ian.campbell@citrix.com>2016-01-15 13:23:41 +0000
committerStefano Stabellini <stefano.stabellini@eu.citrix.com>2016-01-26 17:19:35 +0000
commite0cb42ae4bc4438ba4ec0760df2d830b8759b255 (patch)
treeff913df765bcc06c336d273b2cae9f960d85fa94 /xen-common.c
parent9ed257d1d1c65dbe5a08f207e5106e98384e1860 (diff)
xen: Switch uses of xc_map_foreign_{pages,bulk} to use libxenforeignmemory API.
In Xen 4.7 we are refactoring parts libxenctrl into a number of separate libraries which will provide backward and forward API and ABI compatiblity. One such library will be libxenforeignmemory which provides access to privileged foreign mappings and which will provide an interface equivalent to xc_map_foreign_{pages,bulk}. The new xenforeignmemory_map() function behaves like xc_map_foreign_pages() when the err argument is NULL and like xc_map_foreign_bulk() when err is non-NULL, which maps into the shim here onto checking err == NULL and calling the appropriate old function. Note that xenforeignmemory_map() takes the number of pages before the arrays themselves, in order to support potentially future use of variable-length-arrays in the prototype (in the future, when Xen's baseline toolchain requirements are new enough to ensure VLAs are supported). In preparation for adding support for libxenforeignmemory add support to the <=4.0 and <=4.6 compat code in xen_common.h to allow us to switch to using the new API. These shims will disappear for versions of Xen which include libxenforeignmemory. Since libxenforeignmemory will have its own handle type but for <= 4.6 the functionality is provided by using a libxenctrl handle we introduce a new global xen_fmem alongside the existing xen_xc. In fact we make xen_fmem a pointer to the existing xen_xc, which then works correctly with both <=4.0 (xc handle is an int) and <=4.6 (xc handle is a pointer). In the latter case xen_fmem is actually a double indirect pointer, but it all falls out in the wash. Unlike libxenctrl libxenforeignmemory has an explicit unmap function, rather than just specifying that munmap should be used, so the unmap paths are updated to use xenforeignmemory_unmap, which is a shim for munmap on these versions of xen. The mappings in xen-hvm.c do not appear to be unmapped (which makes sense for a qemu-dm process) In fb_disconnect this results in a change from simply mmap over the existing mapping (with an implicit munmap) to expliclty unmapping with xenforeignmemory_unmap and then mapping the required anonymous memory in the same hole. I don't think this is a problem since any other thread which was racily touching this region would already be running the risk of hitting the mapping halfway through the call. If this is thought to be a problem then we could consider adding an extra API to the libxenforeignmemory interface to replace a foreign mapping with anonymous shared memory, but I'd prefer not to. Signed-off-by: Ian Campbell <ian.campbell@citrix.com> Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Diffstat (limited to 'xen-common.c')
1 files changed, 6 insertions, 0 deletions
diff --git a/xen-common.c b/xen-common.c
index 0dcdbc39f4..6cd2959e21 100644
--- a/xen-common.c
+++ b/xen-common.c
@@ -118,6 +118,12 @@ static int xen_init(MachineState *ms)
xen_be_printf(NULL, 0, "can't open xen interface\n");
return -1;
+ xen_fmem = xenforeignmemory_open(0, 0);
+ if (xen_fmem == NULL) {
+ xen_be_printf(NULL, 0, "can't open xen fmem interface\n");
+ xc_interface_close(xen_xc);
+ return -1;
+ }
qemu_add_vm_change_state_handler(xen_change_state_handler, NULL);