linux/arch/s390/pci/pci_bus.h

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/* SPDX-License-Identifier: GPL-2.0 */
/*
* Copyright IBM Corp. 2020
*
* Author(s):
* Pierre Morel <pmorel@linux.ibm.com>
*
*/
#ifndef __S390_PCI_BUS_H
#define __S390_PCI_BUS_H
#include <linux/pci.h>
int zpci_bus_device_register(struct zpci_dev *zdev, struct pci_ops *ops);
void zpci_bus_device_unregister(struct zpci_dev *zdev);
int zpci_bus_scan_bus(struct zpci_bus *zbus);
s390/pci: separate zbus registration from scanning Now that the zbus can be created without being scanned we can go one step further and make registering a device to a zbus independent from scanning it. This way the zbus handling becomes much more natural in that functions can be registered on the zbus to be scanned later more closely resembling the handling of both real PCI hardware and other virtual PCI busses like Hyper-V's virtual PCI bus (see for example drivers/pci/controller/pci-hyperv.c:create_root_hv_pci_bus()). Having zbus registration separate from scanning allows us to return fully initialized but still disabled zdevs from zpci_create_device() which can then be configured just as we would configure a zdev from standby (minus the SCLP Configure already done by the platform). There is still the exception that a PCI function with non-zero devfn can be plugged before its PCI bus, which depends on the function with zero devfn, is created. In this case the zdev returend from zpci_create_device() is still missing its bus, hotplug slot, and resources which need to be created later but at least it doesn't wait in the enabled state and can otherwise be treated as initialized. With this we also separate the initial PCI scan using CLP List PCI Functions into two phases. In the CLP loop's callback we only register each function with a virtual zbus creating the latter as needed. Then, after we have built this virtual PCI topology based on our list of zbusses, we can make use of the common code functionality to scan each complete zbus as a separate child bus. Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com> Acked-by: Pierre Morel <pmorel@linux.ibm.com> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
2021-02-12 11:57:58 +01:00
void zpci_bus_scan_busses(void);
int zpci_bus_scan_device(struct zpci_dev *zdev);
void zpci_bus_remove_device(struct zpci_dev *zdev, bool set_error);
void zpci_release_device(struct kref *kref);
s390/pci: Allow re-add of a reserved but not yet removed device The architecture assumes that PCI functions can be removed synchronously as PCI events are processed. This however clashes with the reference counting of struct pci_dev which allows device drivers to hold on to a struct pci_dev reference even as the underlying device is removed. To bridge this gap commit 2a671f77ee49 ("s390/pci: fix use after free of zpci_dev") keeps the struct zpci_dev in ZPCI_FN_STATE_RESERVED state until common code releases the struct pci_dev. Only when all references are dropped, the struct zpci_dev can be removed and freed. Later commit a46044a92add ("s390/pci: fix zpci_zdev_put() on reserve") moved the deletion of the struct zpci_dev from the zpci_list in zpci_release_device() to the point where the device is reserved. This was done to prevent handling events for a device that is already being removed, e.g. when the platform generates both PCI event codes 0x304 and 0x308. In retrospect, deletion from the zpci_list in the release function without holding the zpci_list_lock was also racy. A side effect of this handling is that if the underlying device re-appears while the struct zpci_dev is in the ZPCI_FN_STATE_RESERVED state, the new and old instances of the struct zpci_dev and/or struct pci_dev may clash. For example when trying to create the IOMMU sysfs files for the new instance. In this case, re-adding the new instance is aborted. The old instance is removed, and the device will remain absent until the platform issues another event. Fix this by allowing the struct zpci_dev to be brought back up right until it is finally removed. To this end also keep the struct zpci_dev in the zpci_list until it is finally released when all references have been dropped. Deletion from the zpci_list from within the release function is made safe by using kref_put_lock() with the zpci_list_lock. This ensures that the releasing code holds the last reference. Cc: stable@vger.kernel.org Fixes: a46044a92add ("s390/pci: fix zpci_zdev_put() on reserve") Reviewed-by: Gerd Bayer <gbayer@linux.ibm.com> Tested-by: Gerd Bayer <gbayer@linux.ibm.com> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
2025-05-22 14:13:14 +02:00
void zpci_zdev_put(struct zpci_dev *zdev);
s390/pci: fix use after free of zpci_dev The struct pci_dev uses reference counting but zPCI assumed erroneously that the last reference would always be the local reference after calling pci_stop_and_remove_bus_device(). This is usually the case but not how reference counting works and thus inherently fragile. In fact one case where this causes a NULL pointer dereference when on an SRIOV device the function 0 was hot unplugged before another function of the same multi-function device. In this case the second function's pdev->sriov->dev reference keeps the struct pci_dev of function 0 alive even after the unplug. This bug was previously hidden by the fact that we were leaking the struct pci_dev which in turn means that it always outlived the struct zpci_dev. This was fixed in commit 0b13525c20fe ("s390/pci: fix leak of PCI device structure") exposing the broken behavior. Fix this by accounting for the long living reference a struct pci_dev has to its underlying struct zpci_dev via the zbus->function[] array and only release that in pcibios_release_device() ensuring that the struct pci_dev is not left with a dangling reference. This is a minimal fix in the future it would probably better to use fine grained reference counting for struct zpci_dev. Fixes: 05bc1be6db4b2 ("s390/pci: create zPCI bus") Cc: stable@vger.kernel.org Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
2021-08-06 12:11:16 +02:00
static inline void zpci_zdev_get(struct zpci_dev *zdev)
{
kref_get(&zdev->kref);
}
int zpci_alloc_domain(int domain);
void zpci_free_domain(int domain);
PCI: s390: Fix use-after-free of PCI resources with per-function hotplug On s390 PCI functions may be hotplugged individually even when they belong to a multi-function device. In particular on an SR-IOV device VFs may be removed and later re-added. In commit a50297cf8235 ("s390/pci: separate zbus creation from scanning") it was missed however that struct pci_bus and struct zpci_bus's resource list retained a reference to the PCI functions MMIO resources even though those resources are released and freed on hot-unplug. These stale resources may subsequently be claimed when the PCI function re-appears resulting in use-after-free. One idea of fixing this use-after-free in s390 specific code that was investigated was to simply keep resources around from the moment a PCI function first appeared until the whole virtual PCI bus created for a multi-function device disappears. The problem with this however is that due to the requirement of artificial MMIO addreesses (address cookies) extra logic is then needed to keep the address cookies compatible on re-plug. At the same time the MMIO resources semantically belong to the PCI function so tying their lifecycle to the function seems more logical. Instead a simpler approach is to remove the resources of an individually hot-unplugged PCI function from the PCI bus's resource list while keeping the resources of other PCI functions on the PCI bus untouched. This is done by introducing pci_bus_remove_resource() to remove an individual resource. Similarly the resource also needs to be removed from the struct zpci_bus's resource list. It turns out however, that there is really no need to add the MMIO resources to the struct zpci_bus's resource list at all and instead we can simply use the zpci_bar_struct's resource pointer directly. Fixes: a50297cf8235 ("s390/pci: separate zbus creation from scanning") Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com> Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com> Acked-by: Bjorn Helgaas <bhelgaas@google.com> Link: https://lore.kernel.org/r/20230306151014.60913-2-schnelle@linux.ibm.com Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
2023-03-06 16:10:11 +01:00
int zpci_setup_bus_resources(struct zpci_dev *zdev);
static inline struct zpci_dev *zdev_from_bus(struct pci_bus *bus,
unsigned int devfn)
{
struct zpci_bus *zbus = bus->sysdata;
return (devfn >= ZPCI_FUNCTIONS_PER_BUS) ? NULL : zbus->function[devfn];
}
s390/pci: fix PF/VF linking on hot plug Currently there are four places in which a PCI function is scanned and made available to drivers: 1. In pci_scan_root_bus() as part of the initial zbus creation. 2. In zpci_bus_add_devices() when registering a device in configured state on a zbus that has already been scanned. 3. When a function is already known to zPCI (in reserved/standby state) and configuration is triggered through firmware by PEC 0x301. 4. When a device is already known to zPCI (in standby/reserved state) and configuration is triggered from within Linux using enable_slot(). The PF/VF linking step and setting of pdev->is_virtfn introduced with commit e5794cf1a270 ("s390/pci: create links between PFs and VFs") was only triggered for the second case, which is where VFs created through sriov_numvfs usually land. However unlike some other platforms but like POWER VFs can be individually enabled/disabled through /sys/bus/pci/slots. Fix this by doing VF setup as part of pcibios_bus_add_device() which is called in all of the above cases. Finally to remove the PF/VF links call the common code pci_iov_remove_virtfn() function to remove linked VFs. This takes care of the necessary sysfs cleanup. Fixes: e5794cf1a270 ("s390/pci: create links between PFs and VFs") Cc: <stable@vger.kernel.org> # 5.8: 2f0230b2f2d5: s390/pci: re-introduce zpci_remove_device() Cc: <stable@vger.kernel.org> # 5.8 Acked-by: Pierre Morel <pmorel@linux.ibm.com> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
2020-08-03 17:58:10 +02:00
#endif /* __S390_PCI_BUS_H */