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Mon, 24 Feb 2025 11:41:38 GMT Received: from smtpav04.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B622D58050; Mon, 24 Feb 2025 11:41:38 +0000 (GMT) Received: from smtpav04.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C25DE58045; Mon, 24 Feb 2025 11:41:34 +0000 (GMT) Received: from [9.171.81.103] (unknown [9.171.81.103]) by smtpav04.wdc07v.mail.ibm.com (Postfix) with ESMTP; Mon, 24 Feb 2025 11:41:34 +0000 (GMT) Message-ID: <16f499d3b04d0f56463b4b09e722f1900d21858c.camel@linux.ibm.com> Subject: Re: [PATCH v6 3/3] PCI: s390: Enable HAVE_PCI_MMAP on s390 and restrict mmap() of resources to mappable BARs From: Niklas Schnelle To: Bjorn Helgaas , Christoph Hellwig , Alexandra Winter , Alex Williamson , Gerd Bayer , Matthew Rosato , Jason Gunthorpe , Thorsten Winkler , Bjorn Helgaas Cc: Julian Ruess , Halil Pasic , Christian Borntraeger , Sven Schnelle , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-pci@vger.kernel.org Date: Mon, 24 Feb 2025 12:41:33 +0100 In-Reply-To: <20250214-vfio_pci_mmap-v6-3-6f300cb63a7e@linux.ibm.com> References: <20250214-vfio_pci_mmap-v6-0-6f300cb63a7e@linux.ibm.com> <20250214-vfio_pci_mmap-v6-3-6f300cb63a7e@linux.ibm.com> Autocrypt: addr=schnelle@linux.ibm.com; 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charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.3 (3.54.3-1.fc41) 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-ORIG-GUID: oY8kH1XTy1ewNhu2Y-ZEr5Rb6UsG6lpl X-Proofpoint-GUID: l2-s2rE6QjaNhJvvGedEd3NHf88j0tTe X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-02-24_05,2025-02-24_02,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 phishscore=0 priorityscore=1501 impostorscore=0 suspectscore=0 malwarescore=0 spamscore=0 clxscore=1015 mlxlogscore=765 mlxscore=0 bulkscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2502100000 definitions=main-2502240084 On Fri, 2025-02-14 at 14:10 +0100, Niklas Schnelle wrote: > So far s390 does not select HAVE_PCI_MMAP. This is partly because access > to mapped PCI resources requires special PCI load/store instructions and > prior to commit 71ba41c9b1d9 ("s390/pci: provide support for MIO > instructions") even required use of special syscalls. This really isn't > a showstopper though and in fact lack of HAVE_PCI_MMAP has previously > caused extra work when testing and debugging PCI devices and drivers. >=20 > Another issue when looking at HAVE_PCI_MMAP however comes from the > virtual ISM devices. These present 256 TiB BARs which really can't be > accessed via a mapping to user-space. >=20 > Now, the newly added pdev->non_mappable_bars flag provides a way to > exclude devices whose BARs can't be mapped to user-space including the > s390 ISM device. So honor this flag also in the mmap() paths protected > by HAVE_PCI_MMMAP and with the ISM device thus excluded enable > HAVE_PCI_MMAP for s390. >=20 > Note that most distributions enable CONFIG_IO_STRICT_DEVMEM=3Dy and > require unbinding drivers before resources can be mapped. This makes it > extremely unlikely that any existing programs on s390 will now suddenly > fail after succeeding to mmap() resources and then trying to access the > mapping without use of the special PCI instructions. >=20 > Link: https://lore.kernel.org/lkml/20250212132808.08dcf03c.alex.williamso= n@redhat.com/ > Suggested-by: Alex Williamson > Signed-off-by: Niklas Schnelle > --- > arch/s390/include/asm/pci.h | 4 ++++ > drivers/pci/pci-sysfs.c | 4 ++++ > drivers/pci/proc.c | 4 ++++ > 3 files changed, 12 insertions(+) >=20 > diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h > index 474e1f8d1d3c2fc5685b459cc68b67ac651ea3e9..518dd71a78c83c74dc7b29778= e299d5c8cabcc59 100644 > --- a/arch/s390/include/asm/pci.h > +++ b/arch/s390/include/asm/pci.h > @@ -11,6 +11,10 @@ > #include > #include > =20 > +#define HAVE_PCI_MMAP 1 > +#define ARCH_GENERIC_PCI_MMAP_RESOURCE 1 > +#define arch_can_pci_mmap_wc() 1 > + > #define PCIBIOS_MIN_IO 0x1000 > #define PCIBIOS_MIN_MEM 0x10000000 > =20 > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c > index b46ce1a2c5542cdea0a3f9df324434fdb7e8a4d2..7373eca0a4943bf896b4a1771= 24e0d4572baec2b 100644 > --- a/drivers/pci/pci-sysfs.c > +++ b/drivers/pci/pci-sysfs.c > @@ -1257,6 +1257,10 @@ static int pci_create_resource_files(struct pci_de= v *pdev) > int i; > int retval; > =20 > + /* Skip devices with non-mappable BARs */ > + if (pdev->non_mappable_bars) > + return 0; > + > /* Expose the PCI resources from this device as files */ > for (i =3D 0; i < PCI_STD_NUM_BARS; i++) { > =20 > diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c > index f967709082d654a101039091b5493b2dec5f57b4..9348a0fb808477ca9be80a8b8= 8bbc036565bc411 100644 > --- a/drivers/pci/proc.c > +++ b/drivers/pci/proc.c > @@ -251,6 +251,10 @@ static int proc_bus_pci_mmap(struct file *file, stru= ct vm_area_struct *vma) > security_locked_down(LOCKDOWN_PCI_ACCESS)) > return -EPERM; > =20 > + /* Skip devices with non-mappable BARs */ > + if (dev->non_mappable_bars) > + return -EINVAL; > + > if (fpriv->mmap_state =3D=3D pci_mmap_io) { > if (!arch_can_pci_mmap_io()) > return -EINVAL; >=20 Gentle ping