The patch below does not apply to the 5.15-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-5.15.y git checkout FETCH_HEAD git cherry-pick -x c4abe6234246c75cdc43326415d9cff88b7cf06c # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025062021-coastline-bacteria-9de3@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From c4abe6234246c75cdc43326415d9cff88b7cf06c Mon Sep 17 00:00:00 2001 From: Heiko Carstens hca@linux.ibm.com Date: Mon, 19 May 2025 18:07:11 +0200 Subject: [PATCH] s390/pci: Fix __pcilg_mio_inuser() inline assembly

Use "a" constraint for the shift operand of the __pcilg_mio_inuser() inline assembly. The used "d" constraint allows the compiler to use any general purpose register for the shift operand, including register zero.

If register zero is used this my result in incorrect code generation:

8f6: a7 0a ff f8 ahi %r0,-8 8fa: eb 32 00 00 00 0c srlg %r3,%r2,0 <----

If register zero is selected to contain the shift value, the srlg instruction ignores the contents of the register and always shifts zero bits. Therefore use the "a" constraint which does not permit to select register zero.

Fixes: f058599e22d5 ("s390/pci: Fix s390_mmio_read/write with MIO") Cc: stable@vger.kernel.org Reported-by: Niklas Schnelle schnelle@linux.ibm.com Reviewed-by: Niklas Schnelle schnelle@linux.ibm.com Signed-off-by: Heiko Carstens hca@linux.ibm.com

diff --git a/arch/s390/pci/pci_mmio.c b/arch/s390/pci/pci_mmio.c index 9680055edb78..51e7a28af899 100644 --- a/arch/s390/pci/pci_mmio.c +++ b/arch/s390/pci/pci_mmio.c @@ -244,7 +244,7 @@ static inline int __pcilg_mio_inuser( : [ioaddr_len] "+&d" (ioaddr_len.pair), [exc] "+d" (exception), CC_OUT(cc, cc), [val] "=d" (val), [dst] "+a" (dst), [cnt] "+d" (cnt), [tmp] "=d" (tmp), - [shift] "+d" (shift) + [shift] "+a" (shift) : : CC_CLOBBER_LIST("memory")); disable_sacf_uaccess(sacf_flag);