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Mon, 28 Sep 2026 16:15:48 +0000 (GMT) Received: from osiris (unknown [9.87.129.112]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTPS; Mon, 28 Sep 2026 16:15:48 +0000 (GMT) Date: Mon, 28 Sep 2026 18:15:46 +0200 From: Steffen Eiden To: Ilya Leoshkevich 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 , Fuad Tabba , Gautam Gala , Hariharan Mari , Heiko Carstens , Hendrik Brueckner , Janosch Frank , 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 Subject: Re: [PATCH v8 20/29] s390: Introduce Start Arm Execution instruction Message-ID: <20260928161546.428362-B-seiden@linux.ibm.com> References: <20260918133107.1042730-1-seiden@linux.ibm.com> <20260918133107.1042730-21-seiden@linux.ibm.com> <1e3b65b3-0c21-466f-ae09-8426eeacb97d@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1e3b65b3-0c21-466f-ae09-8426eeacb97d@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=FYWiV5+6 c=1 sm=1 tr=0 ts=6aba92bd cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=kj9zAlcOel0A:10 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=e3H7mCSiy_dY2-7_aUoA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-Spam-Info: AW1haW4tMjYwOTI4MDA2NCBTYWx0ZWRfX3FSm3poY32ru XNpcZw6G5JilofWjVWIAL3oP4Ur3C8GgIIfLeX1MeJGeUvA+tByS9z0RHBt9xL4zxRF9vJaef8f NIGNJmu/RKV8WlV/FMOZH0MbVUwyyTg= X-Proofpoint-ORIG-GUID: u7gi_9HJKgoAJZK9_WrkyB0fwXIjcwUQ X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTI4MDA2NCBTYWx0ZWRfX6DJMgiDneped QSRu5a4Y/OkaqXFWEb5fmEwOY/3QV3AbBPgXGGv5B9jhsW5sdO51LB/lWwvdQOuMIX8xx8pHfq4 bEPo7AIYAOxJzo4vgZ+CRTxb8Y5bOVl6Xj1S1suhouAJjFIst8GSNDYQj1otUv9o4eeeqF04Ind 2CIREBrvbcTKBikSaD1MivFC/xg6YfsOEvxK1AS8lTTBuDThSDdJxNZr9lUOmkV9g68YxvZl7tb anrOkjnQMnN6fjMAT035LPxzGd8IAFZ4PDVYNzMWao59alb/XDdFJa141lC7Ux2Vko4KCJEP0t7 InhU1EMnFF9RZBBZGG5NdOUDNVEJHWmaS4b7k/YsA0YpRgk571Ms7AbnAW4IQl2bYyIV5zEP2Tn y9z8eVpGMf0DmsQ8oNmbgk4BhnXNBR+X1WsDJfbgl+HmZCyLDrv8O1Wqv+mRlszk98FPt26E0/0 mYYFsmG+FgH/gT5vd9A== X-Proofpoint-GUID: P2tX3rfu3_XjSxABuwj_-1RkrjrsE3wJ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-09-28_04,2026-09-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 clxscore=1015 impostorscore=0 spamscore=0 phishscore=0 priorityscore=1501 malwarescore=0 bulkscore=0 lowpriorityscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609280064 On Mon, Sep 28, 2026 at 05:53:33PM +0200, Ilya Leoshkevich wrote: > > > On 9/18/26 15:30, Steffen Eiden wrote: > > The Start Arm Execution (SAE) instruction is the centerpiece for > > executing arm64 (KVM) guests on s390. Its purpose is, similar to SIE, to > > enable accelerated execution of arm64 virtual machines. SAE expects the > > physical address of a control block as the only argument. > > > > The host is responsible to save & restore > > - GPRs 0-13 > > - access register 0-15 > ^^^^^^^^ > registers> - breaking event register (BEAR) > > - vector/floating point registers > > between SAE executions to guarantee host consistency. > > > > GPRs and BEAR are save and restores in the asm functions. The other > ^^^^^^^^^^^^^^^^^ > saved and restored > > > register are handled in within C code. Access registers are handled in a > ^^^^^^^^ ^^ > registers not needed probably? > > > later patch and SVEs will be handled when they are introduced in a > > future series. Most arm64 registers are handled by a satellite block > > called save_area. Some registers, frequently used by hypervisors, are > > placed into the SAE control block itself. > > > > Enlighten asm/kvm_host_types.h for the new header variant. The new > > header is chosen instead of asm/kvm_host_s390_types.h if KVM_S390_ARM64 > > is defined. > > > > Co-developed-by: Andreas Grapentin > > Signed-off-by: Andreas Grapentin > > Co-developed-by: Nina Schoetterl-Glausch > > Signed-off-by: Nina Schoetterl-Glausch > > Signed-off-by: Steffen Eiden > > --- > > arch/s390/include/asm/asm-prototypes.h | 1 + > > arch/s390/include/asm/kvm_host_arm64_types.h | 124 +++++++++++++++++++ > > arch/s390/include/asm/kvm_host_types.h | 4 + > > arch/s390/include/asm/sae.h | 58 +++++++++ > > arch/s390/include/asm/stacktrace.h | 5 + > > arch/s390/kernel/asm-offsets.c | 1 + > > arch/s390/kernel/entry.S | 22 ++++ > > arch/s390/tools/opcodes.txt | 3 + > > 8 files changed, 218 insertions(+) > > create mode 100644 arch/s390/include/asm/kvm_host_arm64_types.h > > create mode 100644 arch/s390/include/asm/sae.h > > [...] > > +#if IS_ENABLED(CONFIG_KVM) > > +/* > > + * __sae64a calling convention: > > + * %r2 pointer to sae control block physical address > ^^^^^^^^^^ I guess it's just a physical address and not a > pointer to it? > yes. Fixing. > ^^^ sometimes it's called "sae", sometimes "SAE" - > it would be nice to have some consistency> + */ Thanks, I will convert everything to SAE > > +SYM_FUNC_START(__sae64a) > > + stmg %r6,%r14,__SF_GPRS(%r15) # store kernel registers > > Strictly speaking we don't need to save %r14, but I guess you do this > for unwinding? yes. Also, some later (unsent) patch needs this and before I forget this, let's do it now. > > > + STBEAR __SF_SAE_BEAR(%r15) # save breaking event address register > > + .insn rre,0xb9a50000,%r2,0 # Start Arm Execution > > + LBEAR __SF_SAE_BEAR(%r15) # restore breaking event address register > > + lmg %r6,%r14,__SF_GPRS(%r15) # restore kernel registers > > + xgr %r0,%r0 # clear guest registers to > > + xgr %r1,%r1 # prevent speculative use > > + xgr %r2,%r2 > > + xgr %r3,%r3 > > + xgr %r4,%r4 > > + xgr %r5,%r5 > > + BR_EX %r14 > > +SYM_FUNC_END(__sae64a) > > +EXPORT_SYMBOL(__sae64a) > > +#endif > [...]