On Thu, Oct 30, 2014 at 05:44:48PM +0100, Takashi Iwai wrote: >Hi, > >I've got a warning with the latest Linus tree like below: > >[ INFO: suspicious RCU usage. ] >3.18.0-rc2-test2+ #70 Not tainted >------------------------------- >include/linux/kvm_host.h:474 suspicious rcu_dereference_check() usage! > >other info that might help us debug this: > >rcu_scheduler_active = 1, debug_locks = 0 >1 lock held by qemu-system-x86/2371: > #0: (&vcpu->mutex){+.+...}, at: [<ffffffffa037d800>] vcpu_load+0x20/0xd0 [kvm] > >stack backtrace: >CPU: 4 PID: 2371 Comm: qemu-system-x86 Not tainted 3.18.0-rc2-test2+ #70 >Hardware name: Dell Inc. OptiPlex 9010/0M9KCM, BIOS A12 01/10/2013 > 0000000000000001 ffff880209983ca8 ffffffff816f514f 0000000000000000 > ffff8802099b8990 ffff880209983cd8 ffffffff810bd687 00000000000fee00 > ffff880208a2c000 ffff880208a10000 ffff88020ef50040 ffff880209983d08 >Call Trace: > [<ffffffff816f514f>] dump_stack+0x4e/0x71 > [<ffffffff810bd687>] lockdep_rcu_suspicious+0xe7/0x120 > [<ffffffffa037d055>] gfn_to_memslot+0xd5/0xe0 [kvm] > [<ffffffffa03807d3>] __gfn_to_pfn+0x33/0x60 [kvm] > [<ffffffffa0380885>] gfn_to_page+0x25/0x90 [kvm] > [<ffffffffa038aeec>] kvm_vcpu_reload_apic_access_page+0x3c/0x80 [kvm] The srcu read lock must be held while accessing memslots (e.g. when using gfn_to_* functions, however, kvm_vcpu_reload_apic_access_page() doesn't do this. I will send a patch to fix it after reproducibe. Regards, Wanpeng Li > [<ffffffffa08f0a9c>] vmx_vcpu_reset+0x20c/0x460 [kvm_intel] > [<ffffffffa039ab8e>] kvm_vcpu_reset+0x15e/0x1b0 [kvm] > [<ffffffffa039ac0c>] kvm_arch_vcpu_setup+0x2c/0x50 [kvm] > [<ffffffffa037f7e0>] kvm_vm_ioctl+0x1d0/0x780 [kvm] > [<ffffffff810bc664>] ? __lock_is_held+0x54/0x80 > [<ffffffff812231f0>] do_vfs_ioctl+0x300/0x520 > [<ffffffff8122ee45>] ? __fget+0x5/0x250 > [<ffffffff8122f0fa>] ? __fget_light+0x2a/0xe0 > [<ffffffff81223491>] SyS_ioctl+0x81/0xa0 > [<ffffffff816fed6d>] system_call_fastpath+0x16/0x1b >kvm: zapping shadow pages for mmio generation wraparound >kvm [2369]: vcpu0 disabled perfctr wrmsr: 0xc1 data 0xffff > > >The machine itself and KVM work fine even after this warning. I'm not >sure whether this is new, maybe it's triggered now since I changed my >Kconfig to cover more RCU testing recently. The warning is >reproducible, I can see it at the first invocation of kvm after each >fresh boot. > >Does this ring a bell to anyone? > > >thanks, > >Takashi >-- >To unsubscribe from this list: send the line "unsubscribe kvm" in >the body of a message to majordomo@xxxxxxxxxxxxxxx >More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html