The patch below does not apply to the 6.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.15.y git checkout FETCH_HEAD git cherry-pick -x 3ec8a8330a1aa846dffbf1d64479213366c55b54 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025062033-retold-crinkly-e6e3@gregkh' --subject-prefix 'PATCH 6.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 3ec8a8330a1aa846dffbf1d64479213366c55b54 Mon Sep 17 00:00:00 2001 From: David Hildenbrand david@redhat.com Date: Fri, 16 May 2025 14:39:44 +0200 Subject: [PATCH] s390/uv: Don't return 0 from make_hva_secure() if the operation was not successful

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

diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c index 9a5d5be8acf4..2cc3b599c7fe 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;