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Wed, 10 Jun 2026 08:55:30 +0000 (GMT) Received: from [9.111.52.177] (unknown [9.111.52.177]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 10 Jun 2026 08:55:30 +0000 (GMT) Message-ID: <8280da18-b0db-46c9-b6a7-5864fd945144@linux.ibm.com> Date: Wed, 10 Jun 2026 10:55:29 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 13/26] s390: Introduce read/write ARM sysreg instructions To: Steffen Eiden Cc: kvm@vger.kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, Alexander Gordeev , Andreas Grapentin , Arnd Bergmann , Catalin Marinas , Christian Borntraeger , Claudio Imbrenda , David Hildenbrand , Friedrich Welter , Gautam Gala , Hariharan Mari , Heiko Carstens , Hendrik Brueckner , Ilya Leoshkevich , Joey Gouly , Marc Zyngier , Nico Boehr , Nina Schoetterl-Glausch , Oliver Upton , Paolo Bonzini , Suzuki K Poulose , Sven Schnelle , Ulrich Weigand , Vasily Gorbik , Will Deacon , Zenghui Yu References: <20260529155601.2927240-1-seiden@linux.ibm.com> <20260529155601.2927240-14-seiden@linux.ibm.com> <2d73aca5-1858-4a7a-a304-0971e4789dc1@linux.ibm.com> <20260610083054.151573-A-seiden@linux.ibm.com> Content-Language: en-US From: Janosch Frank Autocrypt: addr=frankja@linux.ibm.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=HppG3UTS c=1 sm=1 tr=0 ts=6a29268b cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VnNF1IyMAAAA:8 a=gP38sU8B_-xW9SrUZJYA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: AGYVd7PxwhujTjbFY4JicdBUrg3CLnTg X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjEwMDA4MSBTYWx0ZWRfXySJu93HLwnzH I01zxkJjq1NQhKkifu+j4cN+yd5mXofIrWct5CdpozPcRCkWpDsQPhqo50T4U+Pyci/+U7hQmIe 7IQlw0zWWTsiUAyM+UWf9Md5RDDoTvVCZ2quuc3BUFB3ssx1lSmhNCgtd+r5ce/xx/DaYXGZ94L 10lktSz0Rxjia7CKhMZKL7pN33rQHOcF0AOlSIjr/WRN3eUQbT6WlQp+yg9DSuDC4OF/PXaW0/w Eus/8M9FNfVL9Vo7QDIWMR00BC4H7lh+PSw5NupuhB4FTkeK1INIhnOVJlKCP198ixRvs0HBV3d G8dFzzsYX5jC3Y+dH1SNHlevZ6LbBMVf897rE9hBIO5bWdiiZd+8t66KQveUItGWEMV+njT/zMh 9DdI6yLg2KB7FULz4Q6EX4GwGZWkihkVb3DhIWvn9aoLL0I+KiJqOA66F2x/VEefz+ycSgCvA1r 44a4P7ZqvYE3rxpu+vQ== X-Proofpoint-ORIG-GUID: AGYVd7PxwhujTjbFY4JicdBUrg3CLnTg X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-10_02,2026-06-09_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 adultscore=0 phishscore=0 malwarescore=0 impostorscore=0 priorityscore=1501 clxscore=1015 bulkscore=0 spamscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2606100081 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260610_015551_844126_2EAD407F X-CRM114-Status: GOOD ( 19.45 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 6/10/26 10:30, Steffen Eiden wrote: > On Tue, Jun 09, 2026 at 05:04:10PM +0200, Janosch Frank wrote: >> On 5/29/26 17:55, Steffen Eiden wrote: >>> Introduce Extract Arm System Register and Store Arm System Register to >>> enable s390 hosts to read and write system registers for arm64 guests. >>> The new instructions use the new RIE_H instruction format. Add assembler >>> macros to create instructions in RIE_H format manually. Add Support for >>> disassembling the new instructions. >>> >>> Co-developed-by: Andreas Grapentin >>> Signed-off-by: Andreas Grapentin >>> Signed-off-by: Steffen Eiden >>> --- >>> arch/s390/include/asm/sae-asm.h | 48 +++++++++++++++++++++++++++ >>> arch/s390/include/asm/sae.h | 58 +++++++++++++++++++++++++++++++++ >>> arch/s390/kernel/dis.c | 1 + >>> arch/s390/tools/opcodes.txt | 2 ++ >>> 4 files changed, 109 insertions(+) >>> create mode 100644 arch/s390/include/asm/sae-asm.h >>> > [...] >>> + * sasr() - Set Arm System Register >>> + * @arm_reg: ARM system register identifier; compile-time constant >>> + * @val: Value to set >>> + * @save_area: Pointer to SAE save area >>> + * @flags: Operation flags; compile-time constant >>> + * >>> + * Sets an ARM system register value. >>> + */ >>> +static __always_inline void sasr(unsigned int arm_reg, u64 val, >>> + struct kvm_sae_save_area *save_area, >>> + u64 flags) >> >> m4 is 4 bits in length, any reason why we use a u64 here? >> Same for easr. >> > > No real reason beside my preference of using u64 by default. > > Do you want me to change it to u8? Yes, that makes the potential problem a bit smaller but also: Since we go through our macro magic I'm not sure if the compiler would complain about values over 4 bits. Did you check for that and if not please do check now. If it does not complain we need a compile time check. Well maybe we should have one either way until the instruction format is available in compilers just to be safe. @Christian: Thoughts?