user-level: 0.896 debug: 0.851 virtual: 0.759 kernel: 0.639 operating system: 0.498 TCG: 0.132 x86: 0.132 device: 0.126 PID: 0.104 ppc: 0.071 hypervisor: 0.058 VMM: 0.057 risc-v: 0.041 files: 0.031 register: 0.028 performance: 0.025 socket: 0.020 i386: 0.016 arm: 0.013 assembly: 0.010 vnc: 0.009 architecture: 0.007 peripherals: 0.006 semantic: 0.005 network: 0.005 KVM: 0.004 alpha: 0.003 boot: 0.003 graphic: 0.003 permissions: 0.003 mistranslation: 0.001 [BUG REPORT] cxl process in infinity loop Hi, all When I did the cxl memory hot-plug test on QEMU, I accidentally connected two memdev to the same downstream port, the command like below: > -object memory-backend-ram,size=262144k,share=on,id=vmem0 \ > -object memory-backend-ram,size=262144k,share=on,id=vmem1 \ > -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \ > -device cxl-rp,port=0,bus=cxl.1,id=root_port0,chassis=0,slot=0 \ > -device cxl-upstream,bus=root_port0,id=us0 \ > -device cxl-downstream,port=0,bus=us0,id=swport00,chassis=0,slot=5 \ > -device cxl-downstream,port=0,bus=us0,id=swport01,chassis=0,slot=7 \ same downstream port but has different slot! > -device cxl-type3,bus=swport00,volatile-memdev=vmem0,id=cxl-vmem0 \ > -device cxl-type3,bus=swport01,volatile-memdev=vmem1,id=cxl-vmem1 \ > -M > cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=64G,cxl-fmw.0.interleave-granularity=4k > \ There is no error occurred when vm start, but when I executed the “cxl list” command to view the CXL objects info, the process can not end properly. Then I used strace to trace the process, I found that the process is in infinity loop: # strace cxl list ...... clock_nanosleep(CLOCK_REALTIME, 0, {tv_sec=0, tv_nsec=1000000}, NULL) = 0 openat(AT_FDCWD, "/sys/bus/cxl/flush", O_WRONLY|O_CLOEXEC) = 3 write(3, "1\n\0", 3) = 3 close(3) = 0 access("/run/udev/queue", F_OK) = 0 clock_nanosleep(CLOCK_REALTIME, 0, {tv_sec=0, tv_nsec=1000000}, NULL) = 0 openat(AT_FDCWD, "/sys/bus/cxl/flush", O_WRONLY|O_CLOEXEC) = 3 write(3, "1\n\0", 3) = 3 close(3) = 0 access("/run/udev/queue", F_OK) = 0 clock_nanosleep(CLOCK_REALTIME, 0, {tv_sec=0, tv_nsec=1000000}, NULL) = 0 openat(AT_FDCWD, "/sys/bus/cxl/flush", O_WRONLY|O_CLOEXEC) = 3 write(3, "1\n\0", 3) = 3 close(3) = 0 access("/run/udev/queue", F_OK) = 0 clock_nanosleep(CLOCK_REALTIME, 0, {tv_sec=0, tv_nsec=1000000}, NULL) = 0 openat(AT_FDCWD, "/sys/bus/cxl/flush", O_WRONLY|O_CLOEXEC) = 3 write(3, "1\n\0", 3) = 3 close(3) = 0 access("/run/udev/queue", F_OK) = 0 clock_nanosleep(CLOCK_REALTIME, 0, {tv_sec=0, tv_nsec=1000000}, NULL) = 0 openat(AT_FDCWD, "/sys/bus/cxl/flush", O_WRONLY|O_CLOEXEC) = 3 write(3, "1\n\0", 3) = 3 close(3) = 0 access("/run/udev/queue", F_OK) = 0 clock_nanosleep(CLOCK_REALTIME, 0, {tv_sec=0, tv_nsec=1000000}, NULL) = 0 openat(AT_FDCWD, "/sys/bus/cxl/flush", O_WRONLY|O_CLOEXEC) = 3 write(3, "1\n\0", 3) = 3 close(3) = 0 access("/run/udev/queue", F_OK) = 0 clock_nanosleep(CLOCK_REALTIME, 0, {tv_sec=0, tv_nsec=1000000}, NULL) = 0 openat(AT_FDCWD, "/sys/bus/cxl/flush", O_WRONLY|O_CLOEXEC) = 3 write(3, "1\n\0", 3) = 3 close(3) = 0 access("/run/udev/queue", F_OK) = 0 clock_nanosleep(CLOCK_REALTIME, 0, {tv_sec=0, tv_nsec=1000000}, NULL) = 0 openat(AT_FDCWD, "/sys/bus/cxl/flush", O_WRONLY|O_CLOEXEC) = 3 write(3, "1\n\0", 3) = 3 close(3) = 0 access("/run/udev/queue", F_OK) = 0 [Environment]: linux: V6.10-rc3 QEMU: V9.0.0 ndctl: v79 I know this is because of the wrong use of the QEMU command, but I think we should be aware of this error in one of the QEMU, OS or ndctl side at least. Thanks Xingtao On Tue, 2 Jul 2024 00:30:06 +0000 "Xingtao Yao (Fujitsu)" wrote: > Hi, all > > When I did the cxl memory hot-plug test on QEMU, I accidentally connected > two memdev to the same downstream port, the command like below: > > > -object memory-backend-ram,size=262144k,share=on,id=vmem0 \ > > -object memory-backend-ram,size=262144k,share=on,id=vmem1 \ > > -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \ > > -device cxl-rp,port=0,bus=cxl.1,id=root_port0,chassis=0,slot=0 \ > > -device cxl-upstream,bus=root_port0,id=us0 \ > > -device cxl-downstream,port=0,bus=us0,id=swport00,chassis=0,slot=5 \ > > -device cxl-downstream,port=0,bus=us0,id=swport01,chassis=0,slot=7 \ > same downstream port but has different slot! > > > -device cxl-type3,bus=swport00,volatile-memdev=vmem0,id=cxl-vmem0 \ > > -device cxl-type3,bus=swport01,volatile-memdev=vmem1,id=cxl-vmem1 \ > > -M > > cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=64G,cxl-fmw.0.interleave-granularity=4k > > \ > > There is no error occurred when vm start, but when I executed the “cxl list” > command to view > the CXL objects info, the process can not end properly. I'd be happy to look preventing this on QEMU side if you send one, but in general there are are lots of ways to shoot yourself in the foot with CXL and PCI device emulation in QEMU so I'm not going to rush to solve this specific one. Likewise, some hardening in kernel / userspace probably makes sense but this is a non compliant switch so priority of a fix is probably fairly low. Jonathan > > Then I used strace to trace the process, I found that the process is in > infinity loop: > # strace cxl list > ...... > clock_nanosleep(CLOCK_REALTIME, 0, {tv_sec=0, tv_nsec=1000000}, NULL) = 0 > openat(AT_FDCWD, "/sys/bus/cxl/flush", O_WRONLY|O_CLOEXEC) = 3 > write(3, "1\n\0", 3) = 3 > close(3) = 0 > access("/run/udev/queue", F_OK) = 0 > clock_nanosleep(CLOCK_REALTIME, 0, {tv_sec=0, tv_nsec=1000000}, NULL) = 0 > openat(AT_FDCWD, "/sys/bus/cxl/flush", O_WRONLY|O_CLOEXEC) = 3 > write(3, "1\n\0", 3) = 3 > close(3) = 0 > access("/run/udev/queue", F_OK) = 0 > clock_nanosleep(CLOCK_REALTIME, 0, {tv_sec=0, tv_nsec=1000000}, NULL) = 0 > openat(AT_FDCWD, "/sys/bus/cxl/flush", O_WRONLY|O_CLOEXEC) = 3 > write(3, "1\n\0", 3) = 3 > close(3) = 0 > access("/run/udev/queue", F_OK) = 0 > clock_nanosleep(CLOCK_REALTIME, 0, {tv_sec=0, tv_nsec=1000000}, NULL) = 0 > openat(AT_FDCWD, "/sys/bus/cxl/flush", O_WRONLY|O_CLOEXEC) = 3 > write(3, "1\n\0", 3) = 3 > close(3) = 0 > access("/run/udev/queue", F_OK) = 0 > clock_nanosleep(CLOCK_REALTIME, 0, {tv_sec=0, tv_nsec=1000000}, NULL) = 0 > openat(AT_FDCWD, "/sys/bus/cxl/flush", O_WRONLY|O_CLOEXEC) = 3 > write(3, "1\n\0", 3) = 3 > close(3) = 0 > access("/run/udev/queue", F_OK) = 0 > clock_nanosleep(CLOCK_REALTIME, 0, {tv_sec=0, tv_nsec=1000000}, NULL) = 0 > openat(AT_FDCWD, "/sys/bus/cxl/flush", O_WRONLY|O_CLOEXEC) = 3 > write(3, "1\n\0", 3) = 3 > close(3) = 0 > access("/run/udev/queue", F_OK) = 0 > clock_nanosleep(CLOCK_REALTIME, 0, {tv_sec=0, tv_nsec=1000000}, NULL) = 0 > openat(AT_FDCWD, "/sys/bus/cxl/flush", O_WRONLY|O_CLOEXEC) = 3 > write(3, "1\n\0", 3) = 3 > close(3) = 0 > access("/run/udev/queue", F_OK) = 0 > clock_nanosleep(CLOCK_REALTIME, 0, {tv_sec=0, tv_nsec=1000000}, NULL) = 0 > openat(AT_FDCWD, "/sys/bus/cxl/flush", O_WRONLY|O_CLOEXEC) = 3 > write(3, "1\n\0", 3) = 3 > close(3) = 0 > access("/run/udev/queue", F_OK) = 0 > > [Environment]: > linux: V6.10-rc3 > QEMU: V9.0.0 > ndctl: v79 > > I know this is because of the wrong use of the QEMU command, but I think we > should > be aware of this error in one of the QEMU, OS or ndctl side at least. > > Thanks > Xingtao