Now that we run the exit handler with preemption disabled, we start
seeing some very ugly things going on:
BUG: scheduling while atomic: qemu-system-arm/1144/0x00000002
Modules linked in:
[<c0015f3c>] (unwind_backtrace+0x0/0xf8) from [<c03f54e0>] (__schedule_bug+0x44/0x58)
[<c03f54e0>] (__schedule_bug+0x44/0x58) from [<c0402690>] (__schedule+0x620/0x644)
[<c0402690>] (__schedule+0x620/0x644) from [<c0402ad8>] (schedule_preempt_disabled+0x24/0x34)
[<c0402ad8>] (schedule_preempt_disabled+0x24/0x34) from [<c04016ac>] (__mutex_lock_slowpath+0x120/0x1a8)
[<c04016ac>] (__mutex_lock_slowpath+0x120/0x1a8) from [<c040176c>] (mutex_lock+0x38/0x3c)
[<c040176c>] (mutex_lock+0x38/0x3c) from [<c0026ab4>] (user_mem_abort.isra.9+0xbc/0x1fc)
[<c0026ab4>] (user_mem_abort.isra.9+0xbc/0x1fc) from [<c00273bc>] (kvm_handle_guest_abort+0xdc/0x164)
[<c00273bc>] (kvm_handle_guest_abort+0xdc/0x164) from [<c0024fcc>] (handle_exit+0x74/0x11c)
[<c0024fcc>] (handle_exit+0x74/0x11c) from [<c00255c0>] (kvm_arch_vcpu_ioctl_run+0x138/0x21c)
[<c00255c0>] (kvm_arch_vcpu_ioctl_run+0x138/0x21c) from [<c002214c>] (kvm_vcpu_ioctl+0x3d8/0x6bc)
[<c002214c>] (kvm_vcpu_ioctl+0x3d8/0x6bc) from [<c00e0990>] (do_vfs_ioctl+0x7c/0x2d0)
[<c00e0990>] (do_vfs_ioctl+0x7c/0x2d0) from [<c00e0c1c>] (sys_ioctl+0x38/0x5c)
[<c00e0c1c>] (sys_ioctl+0x38/0x5c) from [<c000eec0>] (ret_fast_syscall+0x0/0x30)
The culprit is the stage-2 lock, which is defined as a mutex, and
really should be a spinlock.
Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
---
arch/arm/include/asm/kvm_host.h | 2 +-
arch/arm/kvm/arm.c | 2 +-
arch/arm/kvm/mmu.c | 12 ++++++------
3 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 0c7e782..9d0cc83 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -40,7 +40,7 @@ struct kvm_arch {
u32 vmid;
/* 1-level 2nd stage table and lock */
- struct mutex pgd_mutex;
+ spinlock_t pgd_lock;
pgd_t *pgd;
/* VTTBR value associated with above pgd and vmid */
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index f3b206a..44691e1 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -97,7 +97,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
ret = kvm_alloc_stage2_pgd(kvm);
if (ret)
goto out_fail_alloc;
- mutex_init(&kvm->arch.pgd_mutex);
+ spin_lock_init(&kvm->arch.pgd_lock);
ret = create_hyp_mappings(kvm, kvm + 1);
if (ret)
diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 8c30376..4b174e6 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -354,14 +354,14 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
return -EFAULT;
}
- mutex_lock(&vcpu->kvm->arch.pgd_mutex);
+ spin_lock(&vcpu->kvm->arch.pgd_lock);
new_pte = pfn_pte(pfn, PAGE_KVM_GUEST);
if (writable)
new_pte |= L_PTE2_WRITE;
ret = stage2_set_pte(vcpu->kvm, fault_ipa, &new_pte);
if (ret)
put_page(pfn_to_page(pfn));
- mutex_unlock(&vcpu->kvm->arch.pgd_mutex);
+ spin_unlock(&vcpu->kvm->arch.pgd_lock);
return ret;
}
@@ -611,13 +611,13 @@ int kvm_unmap_hva(struct kvm *kvm, unsigned long hva)
if (!kvm->arch.pgd)
return 0;
- mutex_lock(&kvm->arch.pgd_mutex);
+ spin_lock(&kvm->arch.pgd_lock);
found = hva_to_gpa(kvm, hva, &gpa);
if (found) {
stage2_set_pte(kvm, gpa, &null_pte);
__kvm_tlb_flush_vmid(kvm);
}
- mutex_unlock(&kvm->arch.pgd_mutex);
+ spin_unlock(&kvm->arch.pgd_lock);
return 0;
}
@@ -629,7 +629,7 @@ void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte)
if (!kvm->arch.pgd)
return;
- mutex_lock(&kvm->arch.pgd_mutex);
+ spin_lock(&kvm->arch.pgd_lock);
found = hva_to_gpa(kvm, hva, &gpa);
if (found) {
stage2_set_pte(kvm, gpa, &pte);
@@ -640,5 +640,5 @@ void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte)
*/
__kvm_tlb_flush_vmid(kvm);
}
- mutex_unlock(&kvm->arch.pgd_mutex);
+ spin_unlock(&kvm->arch.pgd_lock);
}
--
1.7.10.3
