6.15-stable review patch. If anyone has any objections, please let me know.
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From: David Hildenbrand david@redhat.com
[ Upstream commit 3ec8a8330a1aa846dffbf1d64479213366c55b54 ]
If s390_wiggle_split_folio() returns 0 because splitting a large folio succeeded, we will return 0 from make_hva_secure() even though a retry is required. Return -EAGAIN in that case.
Otherwise, we'll return 0 from gmap_make_secure(), and consequently from unpack_one(). In kvm_s390_pv_unpack(), we assume that unpacking succeeded and skip unpacking this page. Later on, we run into issues and fail booting the VM.
So far, this issue was only observed with follow-up patches where we split large pagecache XFS folios. Maybe it can also be triggered with shmem?
We'll cleanup s390_wiggle_split_folio() a bit next, to also return 0 if no split was required.
Fixes: d8dfda5af0be ("KVM: s390: pv: fix race when making a page secure") Cc: stable@vger.kernel.org Signed-off-by: David Hildenbrand david@redhat.com Link: https://lore.kernel.org/r/20250516123946.1648026-2-david@redhat.com Message-ID: 20250516123946.1648026-2-david@redhat.com Reviewed-by: Claudio Imbrenda imbrenda@linux.ibm.com Signed-off-by: Claudio Imbrenda imbrenda@linux.ibm.com Stable-dep-of: ab73b29efd36 ("s390/uv: Improve splitting of large folios that cannot be split while dirty") Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/kernel/uv.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c index 9a5d5be8acf41..2cc3b599c7fe3 100644 --- a/arch/s390/kernel/uv.c +++ b/arch/s390/kernel/uv.c @@ -393,8 +393,11 @@ int make_hva_secure(struct mm_struct *mm, unsigned long hva, struct uv_cb_header folio_walk_end(&fw, vma); mmap_read_unlock(mm);
- if (rc == -E2BIG || rc == -EBUSY) + if (rc == -E2BIG || rc == -EBUSY) { rc = s390_wiggle_split_folio(mm, folio, rc == -E2BIG); + if (!rc) + rc = -EAGAIN; + } folio_put(folio);
return rc;