From: David Woodhouse dwmw@amazon.co.uk
commit 8228c77d8b56e3f735baf71fefb1b548c23691a7 upstream.
On the preemption path when updating a Xen guest's runstate times, this lock is taken inside the scheduler rq->lock, which is a raw spinlock. This was shown in a lockdep warning:
[ 89.138354] ============================= [ 89.138356] [ BUG: Invalid wait context ] [ 89.138358] 5.15.0-rc5+ #834 Tainted: G S I E [ 89.138360] ----------------------------- [ 89.138361] xen_shinfo_test/2575 is trying to lock: [ 89.138363] ffffa34a0364efd8 (&kvm->arch.pvclock_gtod_sync_lock){....}-{3:3}, at: get_kvmclock_ns+0x1f/0x130 [kvm] [ 89.138442] other info that might help us debug this: [ 89.138444] context-{5:5} [ 89.138445] 4 locks held by xen_shinfo_test/2575: [ 89.138447] #0: ffff972bdc3b8108 (&vcpu->mutex){+.+.}-{4:4}, at: kvm_vcpu_ioctl+0x77/0x6f0 [kvm] [ 89.138483] #1: ffffa34a03662e90 (&kvm->srcu){....}-{0:0}, at: kvm_arch_vcpu_ioctl_run+0xdc/0x8b0 [kvm] [ 89.138526] #2: ffff97331fdbac98 (&rq->__lock){-.-.}-{2:2}, at: __schedule+0xff/0xbd0 [ 89.138534] #3: ffffa34a03662e90 (&kvm->srcu){....}-{0:0}, at: kvm_arch_vcpu_put+0x26/0x170 [kvm] ... [ 89.138695] get_kvmclock_ns+0x1f/0x130 [kvm] [ 89.138734] kvm_xen_update_runstate+0x14/0x90 [kvm] [ 89.138783] kvm_xen_update_runstate_guest+0x15/0xd0 [kvm] [ 89.138830] kvm_arch_vcpu_put+0xe6/0x170 [kvm] [ 89.138870] kvm_sched_out+0x2f/0x40 [kvm] [ 89.138900] __schedule+0x5de/0xbd0
Cc: stable@vger.kernel.org Reported-by: syzbot+b282b65c2c68492df769@syzkaller.appspotmail.com Fixes: 30b5c851af79 ("KVM: x86/xen: Add support for vCPU runstate information") Signed-off-by: David Woodhouse dwmw@amazon.co.uk Message-Id: 1b02a06421c17993df337493a68ba923f3bd5c0f.camel@infradead.org Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/include/asm/kvm_host.h | 2 +- arch/x86/kvm/x86.c | 28 ++++++++++++++-------------- 2 files changed, 15 insertions(+), 15 deletions(-)
--- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1084,7 +1084,7 @@ struct kvm_arch { u64 cur_tsc_generation; int nr_vcpus_matched_tsc;
- spinlock_t pvclock_gtod_sync_lock; + raw_spinlock_t pvclock_gtod_sync_lock; bool use_master_clock; u64 master_kernel_ns; u64 master_cycle_now; --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2537,7 +2537,7 @@ static void kvm_synchronize_tsc(struct k kvm_vcpu_write_tsc_offset(vcpu, offset); raw_spin_unlock_irqrestore(&kvm->arch.tsc_write_lock, flags);
- spin_lock_irqsave(&kvm->arch.pvclock_gtod_sync_lock, flags); + raw_spin_lock_irqsave(&kvm->arch.pvclock_gtod_sync_lock, flags); if (!matched) { kvm->arch.nr_vcpus_matched_tsc = 0; } else if (!already_matched) { @@ -2545,7 +2545,7 @@ static void kvm_synchronize_tsc(struct k }
kvm_track_tsc_matching(vcpu); - spin_unlock_irqrestore(&kvm->arch.pvclock_gtod_sync_lock, flags); + raw_spin_unlock_irqrestore(&kvm->arch.pvclock_gtod_sync_lock, flags); }
static inline void adjust_tsc_offset_guest(struct kvm_vcpu *vcpu, @@ -2775,9 +2775,9 @@ static void kvm_gen_update_masterclock(s kvm_make_mclock_inprogress_request(kvm);
/* no guest entries from this point */ - spin_lock_irqsave(&ka->pvclock_gtod_sync_lock, flags); + raw_spin_lock_irqsave(&ka->pvclock_gtod_sync_lock, flags); pvclock_update_vm_gtod_copy(kvm); - spin_unlock_irqrestore(&ka->pvclock_gtod_sync_lock, flags); + raw_spin_unlock_irqrestore(&ka->pvclock_gtod_sync_lock, flags);
kvm_for_each_vcpu(i, vcpu, kvm) kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu); @@ -2795,15 +2795,15 @@ u64 get_kvmclock_ns(struct kvm *kvm) unsigned long flags; u64 ret;
- spin_lock_irqsave(&ka->pvclock_gtod_sync_lock, flags); + raw_spin_lock_irqsave(&ka->pvclock_gtod_sync_lock, flags); if (!ka->use_master_clock) { - spin_unlock_irqrestore(&ka->pvclock_gtod_sync_lock, flags); + raw_spin_unlock_irqrestore(&ka->pvclock_gtod_sync_lock, flags); return get_kvmclock_base_ns() + ka->kvmclock_offset; }
hv_clock.tsc_timestamp = ka->master_cycle_now; hv_clock.system_time = ka->master_kernel_ns + ka->kvmclock_offset; - spin_unlock_irqrestore(&ka->pvclock_gtod_sync_lock, flags); + raw_spin_unlock_irqrestore(&ka->pvclock_gtod_sync_lock, flags);
/* both __this_cpu_read() and rdtsc() should be on the same cpu */ get_cpu(); @@ -2897,13 +2897,13 @@ static int kvm_guest_time_update(struct * If the host uses TSC clock, then passthrough TSC as stable * to the guest. */ - spin_lock_irqsave(&ka->pvclock_gtod_sync_lock, flags); + raw_spin_lock_irqsave(&ka->pvclock_gtod_sync_lock, flags); use_master_clock = ka->use_master_clock; if (use_master_clock) { host_tsc = ka->master_cycle_now; kernel_ns = ka->master_kernel_ns; } - spin_unlock_irqrestore(&ka->pvclock_gtod_sync_lock, flags); + raw_spin_unlock_irqrestore(&ka->pvclock_gtod_sync_lock, flags);
/* Keep irq disabled to prevent changes to the clock */ local_irq_save(flags); @@ -6101,13 +6101,13 @@ set_pit2_out: * is slightly ahead) here we risk going negative on unsigned * 'system_time' when 'user_ns.clock' is very small. */ - spin_lock_irq(&ka->pvclock_gtod_sync_lock); + raw_spin_lock_irq(&ka->pvclock_gtod_sync_lock); if (kvm->arch.use_master_clock) now_ns = ka->master_kernel_ns; else now_ns = get_kvmclock_base_ns(); ka->kvmclock_offset = user_ns.clock - now_ns; - spin_unlock_irq(&ka->pvclock_gtod_sync_lock); + raw_spin_unlock_irq(&ka->pvclock_gtod_sync_lock);
kvm_make_all_cpus_request(kvm, KVM_REQ_CLOCK_UPDATE); break; @@ -8157,9 +8157,9 @@ static void kvm_hyperv_tsc_notifier(void list_for_each_entry(kvm, &vm_list, vm_list) { struct kvm_arch *ka = &kvm->arch;
- spin_lock_irqsave(&ka->pvclock_gtod_sync_lock, flags); + raw_spin_lock_irqsave(&ka->pvclock_gtod_sync_lock, flags); pvclock_update_vm_gtod_copy(kvm); - spin_unlock_irqrestore(&ka->pvclock_gtod_sync_lock, flags); + raw_spin_unlock_irqrestore(&ka->pvclock_gtod_sync_lock, flags);
kvm_for_each_vcpu(cpu, vcpu, kvm) kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu); @@ -11148,7 +11148,7 @@ int kvm_arch_init_vm(struct kvm *kvm, un
raw_spin_lock_init(&kvm->arch.tsc_write_lock); mutex_init(&kvm->arch.apic_map_lock); - spin_lock_init(&kvm->arch.pvclock_gtod_sync_lock); + raw_spin_lock_init(&kvm->arch.pvclock_gtod_sync_lock);
kvm->arch.kvmclock_offset = -get_kvmclock_base_ns(); pvclock_update_vm_gtod_copy(kvm);