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Wed, 29 Oct 2025 08:37:09 +0000 (GMT) Message-ID: <2d1ea24848d4c389525df63a76fe873723bad900.camel@linux.ibm.com> Subject: Re: [PATCH v2 1/2] PCI: Allow per function PCI slots From: Niklas Schnelle To: Bibo Mao , Farhan Ali , linux-s390@vger.kernel.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Cc: helgaas@kernel.org, mjrosato@linux.ibm.com, bblock@linux.ibm.com, agordeev@linux.ibm.com, gor@linux.ibm.com, hca@linux.ibm.com, stable@vger.kernel.org, Tianrui Zhao , Huacai Chen Date: Wed, 29 Oct 2025 09:37:09 +0100 In-Reply-To: References: <20251022212411.1989-1-alifm@linux.ibm.com> <20251022212411.1989-2-alifm@linux.ibm.com> Autocrypt: addr=schnelle@linux.ibm.com; prefer-encrypt=mutual; keydata=mQINBGHm3M8BEAC+MIQkfoPIAKdjjk84OSQ8erd2OICj98+GdhMQpIjHXn/RJdCZLa58k /ay5x0xIHkWzx1JJOm4Lki7WEzRbYDexQEJP0xUia0U+4Yg7PJL4Dg/W4Ho28dRBROoJjgJSLSHwc 3/1pjpNlSaX/qg3ZM8+/EiSGc7uEPklLYu3gRGxcWV/944HdUyLcnjrZwCn2+gg9ncVJjsimS0ro/ 2wU2RPE4ju6NMBn5Go26sAj1owdYQQv9t0d71CmZS9Bh+2+cLjC7HvyTHKFxVGOznUL+j1a45VrVS XQ+nhTVjvgvXR84z10bOvLiwxJZ/00pwNi7uCdSYnZFLQ4S/JGMs4lhOiCGJhJ/9FR7JVw/1t1G9a UlqVp23AXwzbcoV2fxyE/CsVpHcyOWGDahGLcH7QeitN6cjltf9ymw2spBzpRnfFn80nVxgSYVG1d w75ksBAuQ/3e+oTQk4GAa2ShoNVsvR9GYn7rnsDN5pVILDhdPO3J2PGIXa5ipQnvwb3EHvPXyzakY tK50fBUPKk3XnkRwRYEbbPEB7YT+ccF/HioCryqDPWUivXF8qf6Jw5T1mhwukUV1i+QyJzJxGPh19 /N2/GK7/yS5wrt0Lwxzevc5g+jX8RyjzywOZGHTVu9KIQiG8Pqx33UxZvykjaqTMjo7kaAdGEkrHZ dVHqoPZwhCsgQARAQABtChOaWtsYXMgU2NobmVsbGUgPHNjaG5lbGxlQGxpbnV4LmlibS5jb20+iQ JXBBMBCABBAhsBBQsJCAcCBhUKCQgLAgQWAgMBAh4BAheAAhkBFiEEnbAAstJ1IDCl9y3cr+Q/Fej CYJAFAmesutgFCQenEYkACgkQr+Q/FejCYJDIzA//W5h3t+anRaztihE8ID1c6ifS7lNUtXr0wEKx Qm6EpDQKqFNP+n3R4A5w4gFqKv2JpYQ6UJAAlaXIRTeT/9XdqxQlHlA20QWI7yrJmoYaF74ZI9s/C 8aAxEzQZ64NjHrmrZ/N9q8JCTlyhk5ZEV1Py12I2UH7moLFgBFZsPlPWAjK2NO/ns5UJREAJ04pR9 XQFSBm55gsqkPp028cdoFUD+IajGtW7jMIsx/AZfYMZAd30LfmSIpaPAi9EzgxWz5habO1ZM2++9e W6tSJ7KHO0ZkWkwLKicrqpPvA928eNPxYtjkLB2XipdVltw5ydH9SLq0Oftsc4+wDR8TqhmaUi8qD Fa2I/0NGwIF8hjwSZXtgJQqOTdQA5/6voIPheQIi0NBfUr0MwboUIVZp7Nm3w0QF9SSyTISrYJH6X qLp17NwnGQ9KJSlDYCMCBJ+JGVmlcMqzosnLli6JszAcRmZ1+sd/f/k47Fxy1i6o14z9Aexhq/UgI 5InZ4NUYhf5pWflV41KNupkS281NhBEpChoukw25iZk0AsrukpJ74x69MJQQO+/7PpMXFkt0Pexds XQrtsXYxLDQk8mgjlgsvWl0xlk7k7rddN1+O/alcv0yBOdvlruirtnxDhbjBqYNl8PCbfVwJZnyQ4 SAX2S9XiGeNtWfZ5s2qGReyAcd2nBna0KU5pa2xhcyBTY2huZWxsZSA8bmlrbGFzLnNjaG5lbGxlQ GlibS5jb20+iQJUBBMBCAA+AhsBBQsJCAcCBhUKCQgLAgQWAgMBAh4BAheAFiEEnbAAstJ1IDCl9y 3cr+Q/FejCYJAFAmesuuEFCQenEYkACgkQr+Q/FejCYJCosA/9GCtbN8lLQkW71n/CHR58BAA5ct1 KRYiZNPnNNAiAzjvSb0ezuRVt9H0bk/tnj6pPj0zdyU2bUj9Ok3lgocWhsF2WieWbG4dox5/L1K28 qRf3p+vdPfu7fKkA1yLE5GXffYG3OJnqR7OZmxTnoutj81u/tXO95JBuCSJn5oc5xMQvUUFzLQSbh prIWxcnzQa8AHJ+7nAbSiIft/+64EyEhFqncksmzI5jiJ5edABiriV7bcNkK2d8KviUPWKQzVlQ3p LjRJcJJHUAFzsZlrsgsXyZLztAM7HpIA44yo+AVVmcOlmgPMUy+A9n+0GTAf9W3y36JYjTS+ZcfHU KP+y1TRGRzPrFgDKWXtsl1N7sR4tRXrEuNhbsCJJMvcFgHsfni/f4pilabXO1c5Pf8fiXndCz04V8 ngKuz0aG4EdLQGwZ2MFnZdyf3QbG3vjvx7XDlrdzH0wUgExhd2fHQ2EegnNS4gNHjq82uLPU0hfcr obuI1D74nV0BPDtr7PKd2ryb3JgjUHKRKwok6IvlF2ZHMMXDxYoEvWlDpM1Y7g81NcKoY0BQ3ClXi a7vCaqAAuyD0zeFVGcWkfvxYKGqpj8qaI/mA8G5iRMTWUUUROy7rKJp/y2ioINrCul4NUJUujfx4k 7wFU11/YNAzRhQG4MwoO5e+VY66XnAd+XPyBIlvy0K05pa2xhcyBTY2huZWxsZSA8bmlrbGFzLnNj aG5lbGxlQGdtYWlsLmNvbT6JAlQEEwEIAD4CGwEFCwkIBwIGFQoJCAsCBBYCAwECHgECF4AWIQSds ACy0nUgMKX3Ldyv5D8V6MJgkAUCZ6y64QUJB6cRiQAKCRCv5D8V6MJgkEr/D/9iaYSYYwlmTJELv+ +EjsIxXtneKYpjXEgNnPwpKEXNIpuU/9dcVDcJ10MfvWBPi3sFbIzO9ETIRyZSgrjQxCGSIhlbom4 D8jVzTA698tl9id0FJKAi6T0AnBF7CxyqofPUzAEMSj9ynEJI/Qu8pHWkVp97FdJcbsho6HNMthBl +Qgj9l7/Gm1UW3ZPvGYgU75uB/mkaYtEv0vYrSZ+7fC2Sr/O5SM2SrNk+uInnkMBahVzCHcoAI+6O Enbag+hHIeFbqVuUJquziiB/J4Z2yT/3Ps/xrWAvDvDgdAEr7Kn697LLMRWBhGbdsxdHZ4ReAhc8M 8DOcSWX7UwjzUYq7pFFil1KPhIkHctpHj2Wvdnt+u1F9fN4e3C6lckUGfTVd7faZ2uDoCCkJAgpWR 10V1Q1Cgl09VVaoi6LcGFPnLZfmPrGYiDhM4gyDDQJvTmkB+eMEH8u8V1X30nCFP2dVvOpevmV5Uk onTsTwIuiAkoTNW4+lRCFfJskuTOQqz1F8xVae8KaLrUt2524anQ9x0fauJkl3XdsVcNt2wYTAQ/V nKUNgSuQozzfXLf+cOEbV+FBso/1qtXNdmAuHe76ptwjEfBhfg8L+9gMUthoCR94V0y2+GEzR5nlD 5kfu8ivV/gZvij+Xq3KijIxnOF6pd0QzliKadaFNgGw4FoUeZo0rQhTmlrbGFzIFNjaG5lbGxlIDx uaWtzQGtlcm5lbC5vcmc+iQJUBBMBCAA+AhsBBQsJCAcCBhUKCQgLAgQWAgMBAh4BAheAFiEEnbAA stJ1IDCl9y3cr+Q/FejCYJAFAmesuuEFCQenEYkACgkQr+Q/FejCYJC6yxAAiQQ5NAbWYKpkxxjP/ AajXheMUW8EtK7EMJEKxyemj40laEs0wz9owu8ZDfQl4SPqjjtcRzUW6vE6JvfEiyCLd8gUFXIDMS l2hzuNot3sEMlER9kyVIvemtV9r8Sw1NHvvCjxOMReBmrtg9ooeboFL6rUqbXHW+yb4GK+1z7dy+Q 9DMlkOmwHFDzqvsP7eGJN0xD8MGJmf0L5LkR9LBc+jR78L+2ZpKA6P4jL53rL8zO2mtNQkoUO+4J6 0YTknHtZrqX3SitKEmXE2Is0Efz8JaDRW41M43cE9b+VJnNXYCKFzjiqt/rnqrhLIYuoWCNzSJ49W vt4hxfqh/v2OUcQCIzuzcvHvASmt049ZyGmLvEz/+7vF/Y2080nOuzE2lcxXF1Qr0gAuI+wGoN4gG lSQz9pBrxISX9jQyt3ztXHmH7EHr1B5oPus3l/zkc2Ajf5bQ0SE7XMlo7Pl0Xa1mi6BX6I98CuvPK SA1sQPmo+1dQYCWmdQ+OIovHP9Nx8NP1RB2eELP5MoEW9eBXoiVQTsS6g6OD3rH7xIRxRmuu42Z5e 0EtzF51BjzRPWrKSq/mXIbl5nVW/wD+nJ7U7elW9BoJQVky03G0DhEF6fMJs08DGG3XoKw/CpGtMe 2V1z/FRotP5Fkf5VD3IQGtkxSnO/awtxjlhytigylgrZ4wDpSE= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-2.fc42) Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 7A0yER5TuzicOzdnIqMHgbCjTPW8nSiw X-Authority-Analysis: v=2.4 cv=WPhyn3sR c=1 sm=1 tr=0 ts=6901d23b cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=x6icFKpwvdMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=a3Gw60pZ56dmYUsj_9gA:9 a=QEXdDO2ut3YA:10 a=cPQSjfK2_nFv0Q5t_7PE:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMDI4MDE2NiBTYWx0ZWRfX96rUOvt/9qIL Ic5TsUZZIsg2+IHvZLDQHjOcwHlgVmYUBWVpjgeqyFgMamGCHT0wMHhsB+T9mlDzg/wW38XrvTl NWrULgTMgKI5iIzSh7lRzyNYm0u+M5FvPenkfmF65XpTsG/5ce0DJ3dtznDT+aHHJKO58ZXWICk nhBVxy11hUsCCkp9WmtmRp0HrmGdbSk/Lwdd2q934aObgJVXe+x5ORLtD/ByZ8IJCDyvFnWHaIk +BUPL2ULhSia32c1bRG2VXfSj0KvJC00CGyIUOsfCvXnFhctYHNkkMXyrORmK8r7i/lseCYXWrX KU3HEehASX/agRnYlmZ8iUPq9iDCZLt2Nte0WBjJQg4aI71EPjR9AGRZUS3qS8KR0pdFA6csw4d odjGLO71YrUjekf5d0vdlOW5KLabug== X-Proofpoint-ORIG-GUID: 7A0yER5TuzicOzdnIqMHgbCjTPW8nSiw X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-10-29_03,2025-10-22_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 adultscore=0 malwarescore=0 suspectscore=0 spamscore=0 impostorscore=0 lowpriorityscore=0 clxscore=1015 bulkscore=0 priorityscore=1501 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2510280166 On Tue, 2025-10-28 at 09:11 +0800, Bibo Mao wrote: >=20 > On 2025/10/27 =E4=B8=8B=E5=8D=888:29, Niklas Schnelle wrote: > > On Wed, 2025-10-22 at 14:24 -0700, Farhan Ali wrote: > > > On s390 systems, which use a machine level hypervisor, PCI devices ar= e > > > always accessed through a form of PCI pass-through which fundamentall= y > > > operates on a per PCI function granularity. This is also reflected in= the > > > s390 PCI hotplug driver which creates hotplug slots for individual PC= I > > > functions. Its reset_slot() function, which is a wrapper for > > > zpci_hot_reset_device(), thus also resets individual functions. > > >=20 > > > Currently, the kernel's PCI_SLOT() macro assigns the same pci_slot ob= ject > > > to multifunction devices. This approach worked fine on s390 systems t= hat > > > only exposed virtual functions as individual PCI domains to the opera= ting > > > system. Since commit 44510d6fa0c0 ("s390/pci: Handling multifunction= s") > > > s390 supports exposing the topology of multifunction PCI devices by > > > grouping them in a shared PCI domain. When attempting to reset a func= tion > > > through the hotplug driver, the shared slot assignment causes the wro= ng > > > function to be reset instead of the intended one. It also leaks memor= y as > > > we do create a pci_slot object for the function, but don't correctly = free > > > it in pci_slot_release(). > > >=20 > > > Add a flag for struct pci_slot to allow per function PCI slots for > > > functions managed through a hypervisor, which exposes individual PCI > > > functions while retaining the topology. > >=20 > > I wonder if LoongArch which now also does per PCI function pass-through > > might need this too. Adding their KVM maintainers. >=20 > Hi Niklas, >=20 > Thanks for your reminder. Yes, LoongArch do per PCI function=20 > pass-throught. In theory, function pci_slot_enabled_per_func() should=20 > return true on LoongArch also. Only that now IOMMU driver is not merged,= =20 > there is no way to test it, however we will write down this as a note=20 > inside about this issue and verify it once IOMMU driver is merged. >=20 >=20 > Regards > Bibo Mao >=20 Hi Bibo, Is your ability to test if it works for you also hindered for my other patch touching pci_scan_slot()? It sounded like Huacai was looking into testing that. Thanks, Niklas