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Fri, 28 Nov 2025 13:30:44 GMT Received: from smtpav05.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8AB0658059; Fri, 28 Nov 2025 13:30:44 +0000 (GMT) Received: from smtpav05.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 33C4A58063; Fri, 28 Nov 2025 13:30:41 +0000 (GMT) Received: from [9.87.141.41] (unknown [9.87.141.41]) by smtpav05.wdc07v.mail.ibm.com (Postfix) with ESMTP; Fri, 28 Nov 2025 13:30:41 +0000 (GMT) Message-ID: <298aaf6b2815e59d1a94efffdd0e3b002c000cea.camel@linux.ibm.com> Subject: Re: [PATCH v5 1/2] PCI: Fix isolated PCI function probing with ARI and SR-IOV From: Niklas Schnelle To: Huacai Chen , Tianrui Zhao , Bibo Mao , Bjorn Helgaas Cc: Jan Kiszka , linux-s390 , loongarch@lists.linux.dev, Farhan Ali , Matthew Rosato , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Sven Schnelle , Christian Borntraeger , Gerd Bayer , linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org Date: Fri, 28 Nov 2025 14:30:40 +0100 In-Reply-To: <7385677843a7790e01158644f63ae4dbb3353bfe.camel@linux.ibm.com> References: <20251029-ari_no_bus_dev-v5-0-d9a5eab67ed0@linux.ibm.com> <20251029-ari_no_bus_dev-v5-1-d9a5eab67ed0@linux.ibm.com> <958ef380be4ea488698fab05245d631998c32a48.camel@linux.ibm.com> <8dd0f3df4b18a6c9f8b49ede7bc2ab71e40fd8f9.camel@linux.ibm.com> <7385677843a7790e01158644f63ae4dbb3353bfe.camel@linux.ibm.com> Autocrypt: addr=schnelle@linux.ibm.com; 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charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.1 (3.58.1-1.fc43) 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-Spam-Details-Enc: AW1haW4tMjUxMTIyMDAyMSBTYWx0ZWRfX1d+1eSa76rEn tKZjxRW8cld9HJV7v5UWoaT9TsycbLF4TNVqBAflmv6ZWti0XXsBtnysELI4UWP9nN9m1bJFUR0 tTdP6rOBBzT1ugO6kQyk67TZXxHciUnYCm+4LpPQg1YcEY8PJceV7w3JjVge4acepjmjnfPqElD zcpCqas5xt3R4uSTua5+fTXNWMCK+L4WBG1MxNJZzs1OQqgQbdQP962weaB91TvOtnZbTp0PdX7 hQ3VueHl7RjM6tWb9An5jlbqajqA0LWCZcTeKMLl0k3yj9mUOJGlAQQglJj1raBqVmE2u0c91zz 2lNjrk3GjnUc5NlU9zrRkcsWZowbqM6NaIhOOAzgF835bcLfBti8PLeH337hzqKEN0qxmXnuT3W lueDF3uRYX7/+beXQtqL6F7zT78oUA== X-Authority-Analysis: v=2.4 cv=PLoCOPqC c=1 sm=1 tr=0 ts=6929a407 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=6UeiqGixMTsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=9YU_gSLzOsAJnfYzwUAA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: NdMEprHNgVZa1g7F17S2cOL6dAqG01ZB X-Proofpoint-GUID: 5CoJFNddypBoHofAxD7uoHOt_Pjyya5d X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-11-28_03,2025-11-27_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 lowpriorityscore=0 spamscore=0 adultscore=0 impostorscore=0 priorityscore=1501 bulkscore=0 malwarescore=0 clxscore=1015 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2511220021 On Mon, 2025-11-10 at 14:08 +0100, Niklas Schnelle wrote: > On Fri, 2025-11-07 at 15:19 +0800, Huacai Chen wrote: > > On Wed, Nov 5, 2025 at 5:46=E2=80=AFPM Niklas Schnelle wrote: > > >=20 > > > On Wed, 2025-11-05 at 09:01 +0800, Huacai Chen wrote: > > > > On Mon, Nov 3, 2025 at 7:23=E2=80=AFPM Niklas Schnelle wrote: > > > > >=20 > > > > > On Mon, 2025-11-03 at 17:50 +0800, Huacai Chen wrote: > > > > > > Hi, Niklas, > > > > > >=20 > > > > > > On Wed, Oct 29, 2025 at 5:42=E2=80=AFPM Niklas Schnelle wrote: --- snip --- > > > > > > >=20 > > > > > > > Still especially the first issue prevents correct detection o= f ARI and > > > > > > > the second might be a problem for other users of isolated fun= ction > > > > > > > probing. Fix both issues by keeping things as simple as possi= ble. If > > > > > > > isolated function probing is enabled simply scan every possib= le devfn. > > > > > > I'm very sorry, but applying this patch on top of commit a02fd0= 5661d7 > > > > > > ("PCI: Extend isolated function probing to LoongArch") we fail = to > > > > > > boot. > > > > > >=20 > > > > > > Boot log: > > > > > >=20 --- snip --- > > > > >=20 > > > > >=20 > > > > > This looks like a warning telling us that AHCI enable failed / ti= med > > > > > out. Do you have Panic on Warn on that this directly causes a boo= t > > > > > failure? The only relation I can see with my patch is that maybe = this > > > > > AHCI device wasn't probed before and somehow isn't working? > > > > The rootfs is on the AHCI controller, so AHCI failure causes the bo= ot > > > > failure, without this patch no boot problems. > > > >=20 > > > > Huacai > > > >=20 > > >=20 > > > Ok, I'm going to need more details to make sense of this. Can you tel= l > > > me if ARI is enabled for that bus? Did you test with both patches or > > > just this one? Could you provide lspci -vv from a good boot and can y= ou > > > tell which AHCI device the root device is on? Also could you clarify > > > why you set hypervisor_isolated_pci_functions() in particular this > > > seems like a bare metal boot, right? When running in KVM do you pass- > > > through individual PCI functions with the guest seeing a devfn other > > > than 0 alone, i.e. a missing devfn 0? Or do you need this for bare > > > metal for some reason? If you don't need it for bare metal, does the > > > boot work if you return 0 from hypervisor_isolated_pci_functions() wi= th > > > this patch? > > 1. ARI isn't enabled. > > 2. Only test the first patch. > > 3. This is a bare metal boot. > > 4. If hypervisor_isolated_pci_functions() return 0 then boot is OK > > 5. PCI information please see the attachment. > >=20 > > Huacai >=20 > Thanks for the input. As far as I can see the lspci from a good boot > shows no holes in your devfn space so this particular system doesn't > seem to need the isolated function probing at all. But even then using > it should only try out all devfns and thus never skip one that is found > without isolated function probing. >=20 > To sanity check this, I just booted my personal AMD Ryzen 3900X system > with this series plus a two-liner to unconditionally enable isolated > function probing also on x86_64 and it came up fine including AMD > graphics and my Intel NIC with enabled SR-IOV.=C2=A0 >=20 > So I'm really perplexed and coming back to the thought that a device on > your system is misbehaving when probing is attempted and maybe due to a > similar issue as what I saw with SR-IOV it wasn't probed so far but > really should be probed if isolated function probing is enabled. I also > still don't understand your use-case. If it is for VMs then maybe you > could limit it to those? Otherwise it feels like this is just a hack to > probe an odd topology and I wonder if you should rather set > PCI_SCAN_ALL_PCIE_DEVS to find those? >=20 > Thanks, > Niklas Hi LoongArch Maintainers, Hi Bjorn, Sorry for the ping but I'd really like to somehow get this unstuck and I haven't heard back on my previous questions. From my testing on s390 this patch fixes a real logic error which prevents the scanning of some devfns which I believe should be scanned if isolated functions are possible. And in all my testing, including on x86 as stated in the previous mail, the code does exactly what I think it is supposed to do. So to me it really looks like something goes wrong with your use of hypervisor_isolated_pci_functions() on your specific hardware. One idea I had is if maybe you need to somehow exclude known empty slots in you config space accessors? And just in general I'd really like to better understand your use-case for the isolated PCI functions. And speaking of that, I'm sorry for having been so blunt in my last mail saying that it felt like a hack. I'm just worried, that we've run into incompatible interpretations or uses of this feature that now prevent us from fixing actual bugs. Thanks in advance, Niklas Schnelle