------- Comment From niklas.schne...@ibm.com 2020-05-18 07:18 EDT------- I agree, it's pretty big but this was the least impact approach we could think of and it fixes a kernel crash that can be triggered from user space simply by invoking the s390_pci_read/write_mmio syscalls when running with MIO.
The code mostly mirrors existing PCI code with the addition of the secondary address space access and is otherwise self contained so it should be extremely unlikely to impact anything apart from these two syscalls. With the new PCI instructions that can be used in userspace, these syscalls will not be needed in the future but we of course still need them for applications that have not been updated to use the new instructions. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1874055 Title: [UBUNTU 20.04] s390x/pci: s390_pci_mmio_write/read fail when MIO instructions are available Status in Ubuntu on IBM z Systems: Triaged Status in linux package in Ubuntu: Triaged Bug description: One of the PCI enhancements on Z15 are the enhanced PCI load/store instructions which can be executed directly from user space code. When these instructions are available and preexisting user space code still uses the old s390_pci_mmio_write/read system calls, the system calls fail with an "Unable to handle kernel pointer dereference in virtual kernel address space" in the kernel. This issue affects distributions which have the enablement for Z15 PCI enhancements and where customers run workloads which accesses PCI adapters from user space, e.g. RDMA applications. To solve this, the system call implementation needs to be enhanced to provide to execute enhanced PCI load/store instructions on behalf of the user space application making use of the mappings into its virtual address space To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-z-systems/+bug/1874055/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
