On 12/9/24 3:29 PM, Jan Beulich wrote:
On 27.11.2024 13:50, Oleksii Kurochko wrote:
Introduce set_fixmap() and clear_fixmap() functions to manage mappings
in the fixmap region. The set_fixmap() function maps a 4k page ( as only L0
is expected to be updated; look at setup_fixmap_mappings() ) at a specified
fixmap entry using map_pages_to_xen(), while clear_fixmap() removes the
mapping from a fixmap entry by calling destroy_xen_mappings().
Both functions ensure that the operations succeed by asserting that their
respective calls (map_pages_to_xen() and destroy_xen_mappings()) return 0.
A `BUG_ON` check is used to trigger a failure if any issues occur during
the mapping or unmapping process.
Signed-off-by: Oleksii Kurochko<oleksii.kuroc...@gmail.com>
Acked-by: Jan Beulich<jbeul...@suse.com>
However, ...
@@ -433,3 +434,21 @@ int __init populate_pt_range(unsigned long virt, unsigned
long nr_mfns)
{
return pt_update(virt, INVALID_MFN, nr_mfns, PTE_POPULATE);
}
+
+/* Map a 4k page in a fixmap entry */
+void set_fixmap(unsigned int map, mfn_t mfn, unsigned int flags)
+{
+ int res;
+
+ res = map_pages_to_xen(FIXMAP_ADDR(map), mfn, 1, flags | PTE_SMALL);
+ BUG_ON(res != 0);
+}
... imo in such cases it is preferable to go without a local variable:
if ( map_pages_to_xen(FIXMAP_ADDR(map), mfn, 1, flags | PTE_SMALL) != 0 )
BUG();
I will update that in the next patch version.
Just to double check: Iirc this BUG would in particular trigger when trying
to set a fixmap slot that was already set, and not intermediately cleared?
Yes, correct.
Thanks.
~ Oleksii
