From a73896cb5bbdce672945745db8224352a689f580 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Sun, 2 Nov 2014 07:54:30 +0100 Subject: [PATCH] KVM: vmx: defer load of APIC access page address during reset Most call paths to vmx_vcpu_reset do not hold the SRCU lock. Defer loading the APIC access page to the next vmentry. This avoids the following lockdep splat: [ 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: [] 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: [] dump_stack+0x4e/0x71 [] lockdep_rcu_suspicious+0xe7/0x120 [] gfn_to_memslot+0xd5/0xe0 [kvm] [] __gfn_to_pfn+0x33/0x60 [kvm] [] gfn_to_page+0x25/0x90 [kvm] [] kvm_vcpu_reload_apic_access_page+0x3c/0x80 [kvm] [] vmx_vcpu_reset+0x20c/0x460 [kvm_intel] [] kvm_vcpu_reset+0x15e/0x1b0 [kvm] [] kvm_arch_vcpu_setup+0x2c/0x50 [kvm] [] kvm_vm_ioctl+0x1d0/0x780 [kvm] [] ? __lock_is_held+0x54/0x80 [] do_vfs_ioctl+0x300/0x520 [] ? __fget+0x5/0x250 [] ? __fget_light+0x2a/0xe0 [] SyS_ioctl+0x81/0xa0 [] system_call_fastpath+0x16/0x1b Reported-by: Takashi Iwai Reported-by: Alexei Starovoitov Reviewed-by: Wanpeng Li Tested-by: Wanpeng Li Fixes: 38b9917350cb2946e368ba684cfc33d1672f104e Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index a0f78dbaabee..3e556c68351b 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -4579,7 +4579,7 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu) vmcs_write32(TPR_THRESHOLD, 0); } - kvm_vcpu_reload_apic_access_page(vcpu); + kvm_make_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu); if (vmx_vm_has_apicv(vcpu->kvm)) memset(&vmx->pi_desc, 0, sizeof(struct pi_desc)); -- 2.30.2