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Tue, 14 Apr 2026 10:29:36 +0000 (GMT) Message-ID: Date: Tue, 14 Apr 2026 15:59:35 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] powerpc/fadump: Add timeout to RTAS busy-wait loops To: litaliano00 Cc: maddy@linux.ibm.com, mpe@ellerman.id.au, npiggin@gmail.com, chleroy@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org References: <20260406061542.22354-1-litaliano00.contact@gmail.com> <98adc953-322b-45fa-9128-cdbe831006e1@linux.ibm.com> Content-Language: en-US From: Sourabh Jain In-Reply-To: X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDE0MDA5NiBTYWx0ZWRfX5Dff69lmdZYt 3UQJsgG1r8NtLgwis59qIw+Txng5awEbg+qxG8BWuPNqnCdDQ+CbX2x2a/fVPdK0zqoPLmsfBN0 3WmhwR/8XyG3nrhDofvdTusNhxEwW0s0jSAIGrtCNriA7fjykN0732f43zuWBr9zIr8OLzCYbCF DnY7++7iOAFWUysngqrs58grcX01Q092bzvAeqR7C/S/ZOYoPUOYw0CgRSGEzuAlCUDXX0utw5U StG/2o8j1bvsPS/TbLhRCIGxUSgjMit0Oq6cartyA7VpFM5IFJXMlvBBy+QRZ0GjC/At6a9ybNw qy3nKDAEhfKYRJq4oE0KyfFmq+4Z3qqf2aTmDXHIdJ8ieR+ViX9q+icJBuamhujay+Wg+hmwQry uSUctKCzkSNUxhQ751KNz7/h1SEsEOoA3L3JDruzXEWu9Ddp9tK3/SmISvOp2OrCvRagfQUaudE xcgatzzvFbaipDZKmSg== X-Proofpoint-ORIG-GUID: rX0txqulZupOavtsUAUvfVYhcePFJ-Ll X-Proofpoint-GUID: kosgvy-PTX_qiU9hAVoHq0VnJ_-VxfEf X-Authority-Analysis: v=2.4 cv=fYidDUQF c=1 sm=1 tr=0 ts=69de1715 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=RpNjiQI2AAAA:8 a=VnNF1IyMAAAA:8 a=pGLkceISAAAA:8 a=26oqrSpA1joMOLRANYMA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-04-14_02,2026-04-13_04,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 impostorscore=0 clxscore=1015 malwarescore=0 phishscore=0 bulkscore=0 priorityscore=1501 spamscore=0 suspectscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604070000 definitions=main-2604140096 On 14/04/26 03:07, litaliano00 wrote: > On Mon, Apr 13, 2026, 15:=E2=80=8A50 Sourabh Jain=20 > wrote: > What is t= he rationale behind=20 > choosing a 60-second limit? The 60-second value was chosen somewhat=20 > arbitrarily. Looking at rtas_busy_delay_time(), the maximum >=20 > On Mon, Apr 13, 2026, 15:50 Sourabh Jain =20 > wrote: > > > What is the rationale behind choosing a 60-second limit?=20 > > > The 60-second value was chosen somewhat arbitrarily. Looking at > > rtas_busy_delay_time(), the maximum single delay returned is 100000ms > > (status 9905). In practice, legitimate busy delays are expected to be > > much shorter. I was following the spirit of rtas-rtc.c which uses a > > 5-second limit for simpler operations; fadump is a heavier firmware > > operation, so I went higher. I am open to suggestions on a more > > principled value. > phyp/RTAS is a black box to me, so it is hard to conclude what happens during fadump register/unregister/invalidate. However, based on QEMU's fadump implementation, all three operations do not seem very complex. That said, I am OK with a 60 sec timeout. I would also recommend adding pr_debug logs when the wait time is hit. It might help debug cases where the kernel reaches the 60 sec limit especially during boot. - Sourabh Jain > > > Would it make sense to introduce a helper function to wrap the > > > rtas_call, along with handling the wait time and timeout? > > > Absolutely, I will introduce a helper in v2. The three sites are > > indeed identical except for the FADUMP_REGISTER/UNREGISTER/INVALIDATE > > argument and the struct pointer/size. I will factor out the common > > busy-wait loop into a static helper. > > > Will send v2 shortly from my new email adri.vero.dev@gmail.com > > > Adriano > >