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charset="UTF-8" Content-Transfer-Encoding: quoted-printable Date: Thu, 23 Apr 2026 16:55:29 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Evolution 3.58.3 (3.58.3-1.fc43) X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-GUID: 0cmBSsbFJcSNz14z4SlFVe-xcpTlEpuH X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDIzMDE0OCBTYWx0ZWRfX/Vt1JU5GYUs4 j2gM4cZwvoLJDdh8jGjpN1+6l27twLpWwWqVCcYVf+LFo3kNSotfL+BMy6qmSnSeRE34+aeEkSn hrw71TvQL5c71y75Xd+qdHqAx3uKDRvcCZq3tIjpmWc9nv+BNZSIdMvFAZZM7WSJjjELPlo23/Z aXMzTEh3SUyWSTLWAz6jClqX+Ptc5mp2xt4aJiAcfiDg+poZ02ipfs91Qo6LBvwRFXuF7R6XNhs CjIr2XgO1cdIw2ZbWb2SV7/eSpmhNlpeJUU78cQzLK2WcpAm7eFnin7XY9Lxh/k/JmwaojStX2u iKMMbWNlsUyh/WUkKzQ8oKa9gMkJsOpV6Ykhtwpm137ODm/8aqbm4eFxjlG5zw+HB8t2tAxY7IV kJZ6GHAqXh9KhmDuBwgSt969eMdHgUXNpiYCA1iv5qE2eBRMATSqqxgrpXLIC3/D1VQ39ieonEo dpveVva1A/ZVPrNZ5Fg== X-Authority-Analysis: v=2.4 cv=C8LZDwP+ c=1 sm=1 tr=0 ts=69ea3322 cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=LQvJE2i9nHpm6XaOmtEA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: ye574-iU3Iev19Ib485Mt-TFCoNQW-5B 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=2026-04-23_03,2026-04-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 suspectscore=0 priorityscore=1501 malwarescore=0 lowpriorityscore=0 clxscore=1015 bulkscore=0 impostorscore=0 spamscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604200000 definitions=main-2604230148 On Wed, 2026-04-22 at 18:19 +0300, Leon Romanovsky wrote: > On Wed, Apr 22, 2026 at 03:22:53PM +0100, Matt Evans wrote: > > Hi Leon, > >=20 > > On 21/04/2026 20:49, Leon Romanovsky wrote: > > >=20 > > > On Tue, Apr 21, 2026 at 10:43:51AM -0700, Matt Evans wrote: > > > > Extend pcim_p2pdma_provider()'s checks to exclude functions that ha= ve > > > > pdev->non_mappable_bars set. > > > >=20 > > > > Consumers such as VFIO were previously able to map these for access= by > > > > the CPU or P2P. Update the comment on non_mappable_bars to show it > > > > refers to any access, not just userspace CPU access. > > > >=20 > > > > Fixes: 372d6d1b8ae3c ("PCI/P2PDMA: Refactor to separate core P2P fu= nctionality from memory allocation") > > >=20 > > > I don't object to the patch, but this Fixes line doesn't look correct= . > > > non_mappable_bars applies only to s390, which doesn't support p2p. Th= at > > > wasn't prevented before 372d6d1b8ae3c refactoring too. > >=20 > > Thanks; I'd chosen that commit as it adds the function that the additio= nal > > test is being added to. >=20 > Can I suggest slightly different solution? > If CONFIG_..._S390 is set, we will unset CONFIG_PCI_P2PDMA and pcim_p2pdm= a_provider() > will be compiled to return NULL, without changing non_mappable_bars > description. >=20 > Thanks Hi Leon, I'm not sure this is an ideal solution for the longer term. While ISM definitely can't do P2P and is more akin to an emulated PCI device in its actual implementation, other PCI devices on the platform such as ConnectX family NICs, NVMes and the IBM Spyre Accelerator are much more run off the mill.=C2=A0 So, I'd prefer not to create restrictions unnecessarily. Now there are other unusual properties like the fact that all OSs on s390 run virtualized with PCI functions passed-through by a machine level hypervisor. That and firmware also control root ports and PCIe switches. Still, I don't believe there is anything fundamentally preventing P2P to work in the future. While we could then take this restriction out again, I'd prefer not to introduce it in the first place unless we have to. Thanks, Niklas Schnelle