On 26.01.21 02:14, Oleksandr wrote:
Hello, all
On 26.01.21 01:20, Julien Grall wrote:
Hi Julien, Stefano
On Mon, 25 Jan 2021 at 20:56, Stefano Stabellini
<sstabell...@kernel.org> wrote:
Julien,
Hi,
This seems to be an arm randconfig failure:
https://gitlab.com/xen-project/patchew/xen/-/pipelines/246632953
https://gitlab.com/xen-project/patchew/xen/-/jobs/985455044
Thanks! The error is:
#'target_mem_ref' not supported by expression#'memory.c: In function
'do_memory_op':
memory.c:1210:18: error: may be used uninitialized in this function
[-Werror=maybe-uninitialized]
1210 | rc = set_foreign_p2m_entry(currd, d, gfn_list[i],
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1211 | _mfn(mfn_list[i]));
| ~~~~~~~~~~~~~~~~~~
I found a few references online of the error message, but it is not
clear what it means. From a quick look at Oleksandr's branch, I also
can't spot anything unitialized. Any ideas?
It seems that error happens if *both* CONFIG_GRANT_TABLE and
CONFIG_IOREQ_SERVER are disabled. Looks like that mfn_list is
initialized either in acquire_grant_table() or in acquire_ioreq_server().
If these options disabled then corresponding helpers are just stubs,
so indeed that mfn_list gets uninitialized. But, I am not sure why gcc
complains about it as set_foreign_p2m_entry() is *not* going to be
called in that case???
This weird build error goes away if I simply add:
diff --git a/xen/common/memory.c b/xen/common/memory.c
index 33296e6..d1bd57b 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -1136,7 +1136,7 @@ static int acquire_resource(
* moment since they are small, but if they need to grow in future
* use-cases then per-CPU arrays or heap allocations may be required.
*/
- xen_pfn_t mfn_list[32];
+ xen_pfn_t mfn_list[32] = {0};
int rc;
if ( !arch_acquire_resource_check(currd) )
Shall I make the corresponding patch?
But it is still unclear to me why the compiler doesn't recognize that
*non-yet-uninitialized* mfn_list[] won't be used if both
CONFIG_GRANT_TABLE and CONFIG_IOREQ_SERVER are not set...
--
Regards,
Oleksandr Tyshchenko
