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Mon, 21 Jun 2021 14:39:37 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id CF00142042; Mon, 21 Jun 2021 14:39:36 +0000 (GMT) Received: from ibm-vm (unknown [9.145.9.205]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 21 Jun 2021 14:39:36 +0000 (GMT) Date: Mon, 21 Jun 2021 16:39:35 +0200 From: Claudio Imbrenda To: Heiko Carstens Cc: Christian Borntraeger , Janosch Frank , David Hildenbrand , Cornelia Huck , kvm@vger.kernel.org, linux-s390@vger.kernel.org Subject: Re: [PATCH] KVM: s390: get rid of register asm usage Message-ID: <20210621163935.143dd14a@ibm-vm> In-Reply-To: <20210621140356.1210771-1-hca@linux.ibm.com> References: <20210621140356.1210771-1-hca@linux.ibm.com> Organization: IBM X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: inAKNl4Un0-jkzLLE9IsHowPRx83J7Li X-Proofpoint-ORIG-GUID: phXaZnB9DaYvxCjT8uyms4UQmsNMk-j- X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-06-21_06:2021-06-21,2021-06-21 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 phishscore=0 clxscore=1015 mlxlogscore=999 priorityscore=1501 spamscore=0 malwarescore=0 lowpriorityscore=0 mlxscore=0 adultscore=0 bulkscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2106210086 Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On Mon, 21 Jun 2021 16:03:56 +0200 Heiko Carstens wrote: > Using register asm statements has been proven to be very error prone, > especially when using code instrumentation where gcc may add function > calls, which clobbers register contents in an unexpected way. > > Therefore get rid of register asm statements in kvm code, even though > there is currently nothing wrong with them. This way we know for sure > that this bug class won't be introduced here. > > Reviewed-by: Christian Borntraeger > Signed-off-by: Heiko Carstens Reviewed-by: Claudio Imbrenda > --- > arch/s390/kvm/kvm-s390.c | 18 +++++++++--------- > 1 file changed, 9 insertions(+), 9 deletions(-) > > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c > index 1296fc10f80c..4b7b24f07790 100644 > --- a/arch/s390/kvm/kvm-s390.c > +++ b/arch/s390/kvm/kvm-s390.c > @@ -329,31 +329,31 @@ static void allow_cpu_feat(unsigned long nr) > > static inline int plo_test_bit(unsigned char nr) > { > - register unsigned long r0 asm("0") = (unsigned long) nr | > 0x100; > + unsigned long function = (unsigned long) nr | 0x100; > int cc; > > asm volatile( > + " lgr 0,%[function]\n" > /* Parameter registers are ignored for "test bit" */ > " plo 0,0,0,0(0)\n" > " ipm %0\n" > " srl %0,28\n" > : "=d" (cc) > - : "d" (r0) > - : "cc"); > + : [function] "d" (function) > + : "cc", "0"); > return cc == 0; > } > > static __always_inline void __insn32_query(unsigned int opcode, u8 > *query) { > - register unsigned long r0 asm("0") = 0; /* query > function */ > - register unsigned long r1 asm("1") = (unsigned long) query; > - > asm volatile( > - /* Parameter regs are ignored */ > + " lghi 0,0\n" > + " lgr 1,%[query]\n" > + /* Parameter registers are ignored */ > " .insn rrf,%[opc] << 16,2,4,6,0\n" > : > - : "d" (r0), "a" (r1), [opc] "i" (opcode) > - : "cc", "memory"); > + : [query] "d" ((unsigned long)query), [opc] "i" > (opcode) > + : "cc", "memory", "0", "1"); > } > > #define INSN_SORTL 0xb938