FAILED: patch "[PATCH] s390/pci: Fix __pcilg_mio_inuser() inline assembly" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-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 <[email protected]>.

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-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x c4abe6234246c75cdc43326415d9cff88b7cf06c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025062022-gracious-throttle-46c8@gregkh' --subject-prefix 'PATCH 5.10.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 <[email protected]>
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.

index 9680055edb78..51e7a28af899 100644
@@ -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);

From: Heiko Carstens <[email protected]>

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.

---
 arch/s390/pci/pci_mmio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 6e7c4762bd23..d3be09092a3b 100644
@@ -229,7 +229,7 @@ static inline int __pcilg_mio_inuser(
 		:
 		[cc] "+d" (cc), [val] "=d" (val), [len] "+d" (len),
 		[dst] "+a" (dst), [cnt] "+d" (cnt), [tmp] "=d" (tmp),
-		[shift] "+d" (shift)
+		[shift] "+a" (shift)
 		:
 		[ioaddr] "a" (addr)
 		: "cc", "memory");

2.48.1

[ Sasha's backport helper bot ]

Hi,

Summary of potential issues:
⚠️ Found matching upstream commit but patch is missing proper reference to it

Found matching upstream commit: c4abe6234246c75cdc43326415d9cff88b7cf06c

WARNING: Author mismatch between patch and found commit:
Backport author: Niklas Schnelle<[email protected]> Commit author: Heiko Carstens<[email protected]>

Status in newer kernel trees:
6.15.y | Present (different SHA1: 003d60f4f2af) 6.12.y | Present (different SHA1: 578d93d06043) 6.6.y | Present (different SHA1: cc789e07bb87) 6.1.y | Present (different SHA1: e0e15f95a393) 5.15.y | Present (different SHA1: a8814ec473c6)

Note: The patch differs from the upstream commit:
---

1:  c4abe6234246c < -:  ------------- s390/pci: Fix __pcilg_mio_inuser() inline assembly
-:  ------------- > 1:  9a2f4b3653500 s390/pci: Fix __pcilg_mio_inuser() inline assembly

---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-5.10.y       |  Success    |  Success   |