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Mon, 21 Sep 2026 14:37:23 -0700 (PDT) X-Received: by 2002:a17:902:ebc6:b0:2dd:c053:9c6e with SMTP id d9443c01a7336-2ddc0539da7mr117471595ad.36.1790026642576; Mon, 21 Sep 2026 14:37:22 -0700 (PDT) Received: from localhost ([50.35.44.179]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-33e5ec0d55esm650212eec.20.2026.09.21.14.37.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Sep 2026 14:37:22 -0700 (PDT) Date: Mon, 21 Sep 2026 14:37:18 -0700 From: Jonathan Cameron To: Suzuki K Poulose Cc: kvm@vger.kernel.org, kvmarm@lists.linux.dev, maz@kernel.org, will@kernel.org, catalin.marinas@arm.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, steven.price@arm.com, aneesh.kumar@kernel.org, oupton@kernel.org, gshan@redhat.com, joey.gouly@arm.com, tabba@google.com, yuzenghui@huawei.com, linux-coco@lists.linux.dev, gankulkarni@os.amperecomputing.com, sdonthineni@nvidia.com, alpergun@google.com, fj0570is@fujitsu.com, WeiLin.Chang@arm.com, lpieralisi@kernel.org, enju.kohei@fujitsu.com Subject: Re: [PATCH v18 2/7] firmware: arm_rmm: Check for RMI support at init Message-ID: <20260921143718.00001e55@oss.qualcomm.com> In-Reply-To: References: <20260912083611.2513845-1-suzuki.poulose@arm.com> <20260912083611.2513845-3-suzuki.poulose@arm.com> <178978126541.2352296.3637463397103730192.b4-review@b4> Organization: Qualcomm X-Mailer: Claws Mail 4.4.0 (GTK 3.24.51; x86_64-w64-mingw32) Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Proofpoint-GUID: zn584rcnhT8D-8MvW5Cnbwca4UaYpBKU X-Authority-Analysis: v=2.4 cv=B+0sQ+tM c=1 sm=1 tr=0 ts=6ab1a393 cx=c_pps a=MTSHoo12Qbhz2p7MsH1ifg==:117 a=aNnz9XPx1a4JIXSYt2cE/A==:17 a=kj9zAlcOel0A:10 a=VdqzKS8jKosA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=eoimf2acIAo5FJnRuUoq:22 a=7CQSdrXTAAAA:8 a=dENJxcbTWoohif9XLWkA:9 a=CjuIK1q_8ugA:10 a=GvdueXVYPmCkWapjIL-Q:22 a=a-qgeE7W1pNrGK8U0ZQC:22 X-Proofpoint-Spam-Info: AW1haW4tMjYwOTIxMDMxNSBTYWx0ZWRfX9tnAW0uVdu4B mOvDOtnhkq+TYbCDEf8y/soipNzt3RhGKf5sxHkD68Zp/byEMaV6HekeP9yRRWX+zIZFhtntZfc 69/cbjNrxJpKw6uoOACDiFVDlElbJAA= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTIxMDMxNSBTYWx0ZWRfX3f6aT0JXxg+P lnSsCTNSErmRTKqKKrYkHcguaoG2rx0k2bQ8tXOX8LiJzlYPyvWA3YWuUljOKbQf2kwkS0JCQu5 8jqnhyjwrga8DfGlPBR7NtNJLA2m0z5iAtw1UT4y4jBFFEOb2UOkOHH5GiGJfFxtVO8ylEpJr2Q W698fy+Y4eHAaiDimTDztLTatvz+pHwaReHUM8jmL8M+IvChFfwvu2vNI16jsOBXHen1PPaqLJW 2lImy1W2QyTYPuFak2EcHpUHtSRVy5nBgMPdXTMzEdsAGNA6XaON+U/h+BzRaAHOKRPXNdNmdY5 hHHVV20F8SPlbbo64oWzQjjm7dkhjC30aQKCRGY+2RcWUzjMQsFD9YlJrDkRsEQ/O6nliuAyhDP OXQC4Al7uueRmfGY2BtuDmbXbZMcEreeveuzSrTrMJ/VPAdXIJYNPyAk6S0lduXroS28x7vqxfI TZEQMj3diL/d1vYFr6g== X-Proofpoint-ORIG-GUID: zn584rcnhT8D-8MvW5Cnbwca4UaYpBKU 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=2026-09-21_06,2026-09-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 impostorscore=0 adultscore=0 bulkscore=0 lowpriorityscore=0 suspectscore=0 clxscore=1015 phishscore=0 spamscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609210315 On Mon, 21 Sep 2026 10:00:20 +0100 Suzuki K Poulose wrote: > On 19/09/2026 02:27, Jonathan Cameron wrote: > >> Query the RMI version number and check if it is a compatible version. > >> The first two feature registers are read and exposed for future code to > >> use. > >> > >> We only support this for Little Endian kernels, the Big Endian kernel > >> support is anyway marked BROKEN and is being removed. > > > > Can we have a small comment here on why the default is y > > > > It's a big thing to opt into by default. Feels like defconfig > > material maybe but not in the Kconfig defaults unless I'm missing > > something. > > We need this for KVM arm64. I could drop the default here and > KVM selects this anyways. But, how far do we go on this ? > Do we need to be able to disable this completely even for KVM ? Not sure. Question for the KVM folk to decide. Lot of pre CCA systems out there and domains in which CCA may not be useful, so definitely makes sense that people will build kernels without it. I think dropping this default though makes sense if KVM can select it. Jonathan > > As such it is a relatively smaller blob: > > $ size drivers/firmware/arm_rmm/rmi.o > text data bss dec hex filename > 7477 572 1 8050 1f72 drivers/firmware/arm_rmm/rmi.o > > Cheers > Suzuki >