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Wed, 30 Apr 2025 15:36:15 +0000 (GMT) Received: from smtpav06.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C27F558054; Wed, 30 Apr 2025 15:36:13 +0000 (GMT) Received: from [9.111.36.251] (unknown [9.111.36.251]) by smtpav06.wdc07v.mail.ibm.com (Postfix) with ESMTP; Wed, 30 Apr 2025 15:36:13 +0000 (GMT) Message-ID: Subject: Re: [PATCH 6.1 039/167] s390/pci: Support mmap() of PCI resources except for ISM devices From: Niklas Schnelle To: Greg Kroah-Hartman , stable@vger.kernel.org Cc: patches@lists.linux.dev, Bjorn Helgaas , Sasha Levin Date: Wed, 30 Apr 2025 17:36:12 +0200 In-Reply-To: <20250429161053.337884386@linuxfoundation.org> References: <20250429161051.743239894@linuxfoundation.org> <20250429161053.337884386@linuxfoundation.org> Autocrypt: addr=schnelle@linux.ibm.com; prefer-encrypt=mutual; keydata=mQINBGHm3M8BEAC+MIQkfoPIAKdjjk84OSQ8erd2OICj98+GdhMQpIjHXn/RJdCZLa58k /ay5x0xIHkWzx1JJOm4Lki7WEzRbYDexQEJP0xUia0U+4Yg7PJL4Dg/W4Ho28dRBROoJjgJSLSHwc 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scancount=1 engine=8.19.0-2504070000 definitions=main-2504300111 On Tue, 2025-04-29 at 18:42 +0200, Greg Kroah-Hartman wrote: > 6.1-stable review patch. If anyone has any objections, please let me kno= w. >=20 > ------------------ >=20 > From: Niklas Schnelle >=20 > [ Upstream commit aa9f168d55dc47c0de564f7dfe0e90467c9fee71 ] >=20 > So far s390 does not allow mmap() of PCI resources to user-space via the > usual mechanisms, though it does use it for RDMA. For the PCI sysfs > resource files and /proc/bus/pci it defines neither HAVE_PCI_MMAP nor > ARCH_GENERIC_PCI_MMAP_RESOURCE. For vfio-pci s390 previously relied on > disabled VFIO_PCI_MMAP and now relies on setting pdev->non_mappable_bars > for all devices. >=20 > This is partly because access to mapped PCI resources from user-space > requires special PCI load/store memory-I/O (MIO) instructions, or the > special MMIO syscalls when these are not available. Still, such access is > possible and useful not just for RDMA, in fact not being able to mmap() P= CI > resources has previously caused extra work when testing devices. >=20 > One thing that doesn't work with PCI resources mapped to user-space thoug= h > is the s390 specific virtual ISM device. Not only because the BAR size of > 256 TiB prevents mapping the whole BAR but also because access requires u= se > of the legacy PCI instructions which are not accessible to user-space on > systems with the newer MIO PCI instructions. >=20 > Now with the pdev->non_mappable_bars flag ISM can be excluded from mappin= g > its resources while making this functionality available for all other PCI > devices. To this end introduce a minimal implementation of PCI_QUIRKS and > use that to set pdev->non_mappable_bars for ISM devices only. Then also s= et > ARCH_GENERIC_PCI_MMAP_RESOURCE to take advantage of the generic > implementation of pci_mmap_resource_range() enabling only the newer sysfs > mmap() interface. This follows the recommendation in > Documentation/PCI/sysfs-pci.rst. >=20 > Link: https://lore.kernel.org/r/20250226-vfio_pci_mmap-v7-3-c5c0f1d26efd@= linux.ibm.com > Signed-off-by: Niklas Schnelle > Signed-off-by: Bjorn Helgaas > Signed-off-by: Sasha Levin > --- > arch/s390/Kconfig | 4 +--- > arch/s390/include/asm/pci.h | 3 +++ > arch/s390/pci/Makefile | 2 +- > arch/s390/pci/pci_fixup.c | 23 +++++++++++++++++++++++ > drivers/s390/net/ism_drv.c | 1 - > include/linux/pci_ids.h | 1 + > 6 files changed, 29 insertions(+), 5 deletions(-) > create mode 100644 arch/s390/pci/pci_fixup.c >=20 > diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig > index de575af02ffea..50a4a878bae6d 100644 > --- a/arch/s390/Kconfig > +++ b/arch/s390/Kconfig > @@ -38,9 +38,6 @@ config AUDIT_ARCH > config NO_IOPORT_MAP > def_bool y > =20 > -config PCI_QUIRKS > - def_bool n > - > config ARCH_SUPPORTS_UPROBES > def_bool y > =20 > @@ -213,6 +210,7 @@ config S390 > select PCI_DOMAINS if PCI > select PCI_MSI if PCI > select PCI_MSI_ARCH_FALLBACKS if PCI_MSI > + select PCI_QUIRKS if PCI > select SPARSE_IRQ > select SWIOTLB > select SYSCTL_EXCEPTION_TRACE > diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h > index 108e732d7b140..a4e9a6ecbd437 100644 > --- a/arch/s390/include/asm/pci.h > +++ b/arch/s390/include/asm/pci.h > @@ -11,6 +11,9 @@ > #include > #include > =20 > +#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/arch/s390/pci/Makefile b/arch/s390/pci/Makefile > index eeef68901a15c..2f8dd3f688391 100644 > --- a/arch/s390/pci/Makefile > +++ b/arch/s390/pci/Makefile > @@ -5,5 +5,5 @@ > =20 > obj-$(CONFIG_PCI) +=3D pci.o pci_irq.o pci_dma.o pci_clp.o pci_sysfs.o \ > pci_event.o pci_debug.o pci_insn.o pci_mmio.o \ > - pci_bus.o pci_kvm_hook.o pci_report.o > + pci_bus.o pci_kvm_hook.o pci_report.o pci_fixup.o > obj-$(CONFIG_PCI_IOV) +=3D pci_iov.o > diff --git a/arch/s390/pci/pci_fixup.c b/arch/s390/pci/pci_fixup.c > new file mode 100644 > index 0000000000000..35688b6450983 > --- /dev/null > +++ b/arch/s390/pci/pci_fixup.c > @@ -0,0 +1,23 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Exceptions for specific devices, > + * > + * Copyright IBM Corp. 2025 > + * > + * Author(s): > + * Niklas Schnelle > + */ > +#include > + > +static void zpci_ism_bar_no_mmap(struct pci_dev *pdev) > +{ > + /* > + * ISM's BAR is special. Drivers written for ISM know > + * how to handle this but others need to be aware of their > + * special nature e.g. to prevent attempts to mmap() it. > + */ > + pdev->non_mappable_bars =3D 1; > +} As already noted by others and for other versions the above will cause a build error without also pulling in commit 888bd8322dfc ("s390/pci: Introduce pdev->non_mappable_bars and replace VFIO_PCI_MMAP") > +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_IBM, > + PCI_DEVICE_ID_IBM_ISM, > + zpci_ism_bar_no_mmap); >=20 --- snip ---