From 79a8059d244e99454e474902e4325ee9b50e9178 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Mon, 21 Sep 2015 07:46:55 +0200 Subject: [PATCH] KVM: svm: do not call kvm_set_cr0 from init_vmcb kvm_set_cr0 may want to call kvm_zap_gfn_range and thus access the memslots array (SRCU protected). Using a mini SRCU critical section is ugly, and adding it to kvm_arch_vcpu_create doesn't work because the VMX vcpu_create callback calls synchronize_srcu. Fixes this lockdep splat: =============================== [ INFO: suspicious RCU usage. ] 4.3.0-rc1+ #1 Not tainted ------------------------------- include/linux/kvm_host.h:488 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-i38/17000: #0: (&(&kvm->mmu_lock)->rlock){+.+...}, at: kvm_zap_gfn_range+0x24/0x1a0 [kvm] [...] Call Trace: dump_stack+0x4e/0x84 lockdep_rcu_suspicious+0xfd/0x130 kvm_zap_gfn_range+0x188/0x1a0 [kvm] kvm_set_cr0+0xde/0x1e0 [kvm] init_vmcb+0x760/0xad0 [kvm_amd] svm_create_vcpu+0x197/0x250 [kvm_amd] kvm_arch_vcpu_create+0x47/0x70 [kvm] kvm_vm_ioctl+0x302/0x7e0 [kvm] ? __lock_is_held+0x51/0x70 ? __fget+0x101/0x210 do_vfs_ioctl+0x2f4/0x560 ? __fget_light+0x29/0x90 SyS_ioctl+0x4c/0x90 entry_SYSCALL_64_fastpath+0x16/0x73 Reported-by: Borislav Petkov Signed-off-by: Paolo Bonzini --- arch/x86/kvm/svm.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 89173af53c84..94b7d15db3fc 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -202,6 +202,7 @@ module_param(npt, int, S_IRUGO); static int nested = true; module_param(nested, int, S_IRUGO); +static void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0); static void svm_flush_tlb(struct kvm_vcpu *vcpu); static void svm_complete_interrupts(struct vcpu_svm *svm); @@ -1263,7 +1264,7 @@ static void init_vmcb(struct vcpu_svm *svm, bool init_event) * svm_set_cr0() sets PG and WP and clears NW and CD on save->cr0. * It also updates the guest-visible cr0 value. */ - (void)kvm_set_cr0(&svm->vcpu, X86_CR0_NW | X86_CR0_CD | X86_CR0_ET); + svm_set_cr0(&svm->vcpu, X86_CR0_NW | X86_CR0_CD | X86_CR0_ET); kvm_mmu_reset_context(&svm->vcpu); save->cr4 = X86_CR4_PAE;