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[2003:d8:2f47:4700:e6f9:f453:9ece:7602]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-3a35ca62c70sm2792386f8f.54.2025.05.16.05.39.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 16 May 2025 05:39:49 -0700 (PDT) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-s390@vger.kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org, David Hildenbrand , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Sven Schnelle , Thomas Huth , Matthew Wilcox , Zi Yan , Sebastian Mitterle , stable@vger.kernel.org Subject: [PATCH v1 1/3] s390/uv: don't return 0 from make_hva_secure() if the operation was not successful Date: Fri, 16 May 2025 14:39:44 +0200 Message-ID: <20250516123946.1648026-2-david@redhat.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250516123946.1648026-1-david@redhat.com> References: <20250516123946.1648026-1-david@redhat.com> Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- 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; -- 2.49.0