Since there is no srcu read lock around kvmppc_h_page_init(), a "suspicious rcu_dereference_check() usage" can be triggered by running host linux with CONFIG_PROVE_RCU=y and the following code in the guest: plpar_hcall_norets(H_PAGE_INIT, H_ZERO_PAGE, phys_addr, 0); ============================= WARNING: suspicious RCU usage 7.0.0-dirty #227 Not tainted ----------------------------- ./include/linux/kvm_host.h:1074 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 1 lock held by qemu-system-ppc/2093: #0: c000000354197ab0 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x10c/0xaf0 stack backtrace: CPU: 30 UID: 0 PID: 2093 Comm: qemu-system-ppc Not tainted 7.0.0-dirty #227 PREEMPT(full) Hardware name: IBM,9080-HEX POWER10 (architected) 0x800200 0xf000006 of:IBM,FW1060.60 (NH1060_158) hv:phyp pSeries Call Trace: [c00000033e1bf430] [c000000001b3dbd4] dump_stack_lvl+0xc8/0x130 (unreliable) [c00000033e1bf470] [c0000000003da964] lockdep_rcu_suspicious+0x1f4/0x290 [c00000033e1bf520] [c000000000231424] gfn_to_memslot+0x1b4/0x1c0 [c00000033e1bf560] [c00000000023637c] kvm_clear_guest+0x9c/0x110 [c00000033e1bf5c0] [c0000000002714a4] kvmppc_h_page_init+0x160/0x1a0 [c00000033e1bf610] [c00000000026c040] kvmppc_pseries_do_hcall+0x1930/0x1940 [c00000033e1bf6d0] [c00000000026fb18] kvmppc_vcpu_run_hv+0x268/0x800 [c00000033e1bf7a0] [c000000000246b30] kvmppc_vcpu_run+0x30/0x50 [c00000033e1bf7c0] [c000000000241ed4] kvm_arch_vcpu_ioctl_run+0x364/0x530 [c00000033e1bf860] [c00000000022b870] kvm_vcpu_ioctl+0x1b0/0xaf0 [c00000033e1bfa50] [c0000000009b4514] sys_ioctl+0x144/0x190 [c00000033e1bfab0] [c000000000034330] system_call_exception+0x170/0x370 [c00000033e1bfe50] [c00000000000d05c] system_call_vectored_common+0x15c/0x2ec Fix this by taking a srcu read lock around kvmppc_h_page_init(). Fixes: 2d34d1c3bbfd ("KVM: PPC: Book3S HV: Implement virtual mode H_PAGE_INIT handler") Cc: stable@vger.kernel.org # 5.2+ Signed-off-by: Gautam Menghani --- v3: 1. Use srcu_read_{lock/unlock} instead of the vcpu_srcu* variants (Ritesh) v2: None arch/powerpc/kvm/book3s_hv.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index de05d721edc4..3ed033d4f80f 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -1386,9 +1386,11 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu) ret = kvmhv_copy_tofrom_guest_nested(vcpu); break; case H_PAGE_INIT: + idx = srcu_read_lock(&kvm->srcu); ret = kvmppc_h_page_init(vcpu, kvmppc_get_gpr(vcpu, 4), kvmppc_get_gpr(vcpu, 5), kvmppc_get_gpr(vcpu, 6)); + srcu_read_unlock(&kvm->srcu, idx); break; case H_SVM_PAGE_IN: ret = H_UNSUPPORTED; -- 2.54.0