From 2862a2fdfae875888e3c1c3634e3422e01d98147 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Thu, 11 May 2023 17:04:41 +0200 Subject: [PATCH] s390/qdio: fix do_sqbs() inline assembly constraint Use "a" constraint instead of "d" constraint to pass the state parameter to the do_sqbs() inline assembly. This prevents that general purpose register zero is used for the state parameter. If the compiler would select general purpose register zero this would be problematic for the used instruction in rsy format: the register used for the state parameter is a base register. If the base register is general purpose register zero the contents of the register are unexpectedly ignored when the instruction is executed. This only applies to z/VM guests using QIOASSIST with dedicated (pass through) QDIO-based devices such as FCP [zfcp driver] as well as real OSA or HiperSockets [qeth driver]. A possible symptom for this case using zfcp is the following repeating kernel message pattern: zfcp : A QDIO problem occurred zfcp : A QDIO problem occurred zfcp : qdio: ZFCP on SC using AI:1 QEBSM:1 PRI:1 TDD:1 SIGA: W zfcp : A QDIO problem occurred zfcp : A QDIO problem occurred Each of the qdio problem message can be accompanied by the following entries for the affected subchannel in /sys/kernel/debug/s390dbf/qdio_error/hex_ascii for zfcp or qeth: ccq: 69.... SQBS ERROR. Reviewed-by: Benjamin Block Cc: Steffen Maier Fixes: 8129ee164267 ("[PATCH] s390: qdio V=V pass-through") Cc: Signed-off-by: Heiko Carstens Signed-off-by: Alexander Gordeev --- drivers/s390/cio/qdio.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/s390/cio/qdio.h b/drivers/s390/cio/qdio.h index 5ea6249d8180..641f0dbb65a9 100644 --- a/drivers/s390/cio/qdio.h +++ b/drivers/s390/cio/qdio.h @@ -95,7 +95,7 @@ static inline int do_sqbs(u64 token, unsigned char state, int queue, " lgr 1,%[token]\n" " .insn rsy,0xeb000000008a,%[qs],%[ccq],0(%[state])" : [ccq] "+&d" (_ccq), [qs] "+&d" (_queuestart) - : [state] "d" ((unsigned long)state), [token] "d" (token) + : [state] "a" ((unsigned long)state), [token] "d" (token) : "memory", "cc", "1"); *count = _ccq & 0xff; *start = _queuestart & 0xff;