Re: [PATCH] kvm: use the correct RCU API

From: Paul E. McKenney
Date: Tue Apr 20 2010 - 17:55:51 EST

On Mon, Apr 19, 2010 at 05:41:23PM +0800, Lai Jiangshan wrote:
> The RCU/SRCU API have already changed for proving RCU usage.
>
> I got the following dmesg when PROVE_RCU=y because we used incorrect API.
> This patch coverts rcu_deference() to srcu_dereference() or family API.
>
> ===================================================
> [ INFO: suspicious rcu_dereference_check() usage. ]
> ---------------------------------------------------
> arch/x86/kvm/mmu.c:3020 invoked rcu_dereference_check() without protection!
>
> other info that might help us debug this:
>
>
> rcu_scheduler_active = 1, debug_locks = 0
> 2 locks held by qemu-system-x86/8550:
> #0: (&kvm->slots_lock){+.+.+.}, at: [<ffffffffa011a6ac>] kvm_set_memory_region+0x29/0x50 [kvm]
> #1: (&(&kvm->mmu_lock)->rlock){+.+...}, at: [<ffffffffa012262d>] kvm_arch_commit_memory_region+0xa6/0xe2 [kvm]
>
> stack backtrace:
> Pid: 8550, comm: qemu-system-x86 Not tainted 2.6.34-rc4-tip-01028-g939eab1 #27
> Call Trace:
> [<ffffffff8106c59e>] lockdep_rcu_dereference+0xaa/0xb3
> [<ffffffffa012f6c1>] kvm_mmu_calculate_mmu_pages+0x44/0x7d [kvm]
> [<ffffffffa012263e>] kvm_arch_commit_memory_region+0xb7/0xe2 [kvm]
> [<ffffffffa011a5d7>] __kvm_set_memory_region+0x636/0x6e2 [kvm]
> [<ffffffffa011a6ba>] kvm_set_memory_region+0x37/0x50 [kvm]
> [<ffffffffa015e956>] vmx_set_tss_addr+0x46/0x5a [kvm_intel]
> [<ffffffffa0126592>] kvm_arch_vm_ioctl+0x17a/0xcf8 [kvm]
> [<ffffffff810a8692>] ? unlock_page+0x27/0x2c
> [<ffffffff810bf879>] ? __do_fault+0x3a9/0x3e1
> [<ffffffffa011b12f>] kvm_vm_ioctl+0x364/0x38d [kvm]
> [<ffffffff81060cfa>] ? up_read+0x23/0x3d
> [<ffffffff810f3587>] vfs_ioctl+0x32/0xa6
> [<ffffffff810f3b19>] do_vfs_ioctl+0x495/0x4db
> [<ffffffff810e6b2f>] ? fget_light+0xc2/0x241
> [<ffffffff810e416c>] ? do_sys_open+0x104/0x116
> [<ffffffff81382d6d>] ? retint_swapgs+0xe/0x13
> [<ffffffff810f3ba6>] sys_ioctl+0x47/0x6a
> [<ffffffff810021db>] system_call_fastpath+0x16/0x1b

I have queued this one up, thank you, Lai!

Thanx, Paul

> Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
> ---
> diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
> index 73c5c2b..52b8ece 100644
> --- a/arch/ia64/kvm/kvm-ia64.c
> +++ b/arch/ia64/kvm/kvm-ia64.c
> @@ -1379,7 +1379,7 @@ static void kvm_release_vm_pages(struct kvm *kvm)
> int i, j;
> unsigned long base_gfn;
>
> - slots = rcu_dereference(kvm->memslots);
> + slots = kvm_memslots(kvm);
> for (i = 0; i < slots->nmemslots; i++) {
> memslot = &slots->memslots[i];
> base_gfn = memslot->base_gfn;
> diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
> index 60f09ab..cfa9d17 100644
> --- a/arch/s390/kvm/kvm-s390.h
> +++ b/arch/s390/kvm/kvm-s390.h
> @@ -72,7 +72,7 @@ static inline void kvm_s390_vcpu_set_mem(struct kvm_vcpu *vcpu)
> struct kvm_memslots *memslots;
>
> idx = srcu_read_lock(&vcpu->kvm->srcu);
> - memslots = rcu_dereference(vcpu->kvm->memslots);
> + memslots = kvm_memslots(vcpu->kvm);
>
> mem = &memslots->memslots[0];
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 71faa04..bb61881 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -792,7 +792,7 @@ static int kvm_handle_hva(struct kvm *kvm, unsigned long hva,
> int retval = 0;
> struct kvm_memslots *slots;
>
> - slots = rcu_dereference(kvm->memslots);
> + slots = kvm_memslots(kvm);
>
> for (i = 0; i < slots->nmemslots; i++) {
> struct kvm_memory_slot *memslot = &slots->memslots[i];
> @@ -3017,7 +3017,8 @@ unsigned int kvm_mmu_calculate_mmu_pages(struct kvm *kvm)
> unsigned int nr_pages = 0;
> struct kvm_memslots *slots;
>
> - slots = rcu_dereference(kvm->memslots);
> + slots = kvm_memslots(kvm);
> +
> for (i = 0; i < slots->nmemslots; i++)
> nr_pages += slots->memslots[i].npages;
>
> @@ -3292,7 +3293,7 @@ static int count_rmaps(struct kvm_vcpu *vcpu)
> int i, j, k, idx;
>
> idx = srcu_read_lock(&kvm->srcu);
> - slots = rcu_dereference(kvm->memslots);
> + slots = kvm_memslots(kvm);
> for (i = 0; i < KVM_MEMORY_SLOTS; ++i) {
> struct kvm_memory_slot *m = &slots->memslots[i];
> struct kvm_rmap_desc *d;
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 077cac5..725e7b6 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -1514,7 +1514,7 @@ static gva_t rmode_tss_base(struct kvm *kvm)
> struct kvm_memslots *slots;
> gfn_t base_gfn;
>
> - slots = rcu_dereference(kvm->memslots);
> + slots = kvm_memslots(kvm);
> base_gfn = kvm->memslots->memslots[0].base_gfn +
> kvm->memslots->memslots[0].npages - 3;
> return base_gfn << PAGE_SHIFT;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 6120e33..4dcd62c 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2408,7 +2408,7 @@ gfn_t unalias_gfn_instantiation(struct kvm *kvm, gfn_t gfn)
> struct kvm_mem_alias *alias;
> struct kvm_mem_aliases *aliases;
>
> - aliases = rcu_dereference(kvm->arch.aliases);
> + aliases = kvm_aliases(kvm);
>
> for (i = 0; i < aliases->naliases; ++i) {
> alias = &aliases->aliases[i];
> @@ -2427,7 +2427,7 @@ gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn)
> struct kvm_mem_alias *alias;
> struct kvm_mem_aliases *aliases;
>
> - aliases = rcu_dereference(kvm->arch.aliases);
> + aliases = kvm_aliases(kvm);
>
> for (i = 0; i < aliases->naliases; ++i) {
> alias = &aliases->aliases[i];
> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> index 2d10163..e218fed 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -65,4 +65,11 @@ static inline int is_paging(struct kvm_vcpu *vcpu)
> return kvm_read_cr0_bits(vcpu, X86_CR0_PG);
> }
>
> +static inline struct kvm_mem_aliases *kvm_aliases(struct kvm *kvm)
> +{
> + return rcu_dereference_check(kvm->arch.aliases,
> + srcu_read_lock_held(&kvm->srcu)
> + || lockdep_is_held(&kvm->slots_lock));
> +}
> +
> #endif
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index a3fd0f9..f735752 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -239,6 +239,13 @@ void kvm_exit(void);
> void kvm_get_kvm(struct kvm *kvm);
> void kvm_put_kvm(struct kvm *kvm);
>
> +static inline struct kvm_memslots *kvm_memslots(struct kvm *kvm)
> +{
> + return rcu_dereference_check(kvm->memslots,
> + srcu_read_lock_held(&kvm->srcu)
> + || lockdep_is_held(&kvm->slots_lock));
> +}
> +
> #define HPA_MSB ((sizeof(hpa_t) * 8) - 1)
> #define HPA_ERR_MASK ((hpa_t)1 << HPA_MSB)
> static inline int is_error_hpa(hpa_t hpa) { return hpa >> HPA_MSB; }
> diff --git a/virt/kvm/iommu.c b/virt/kvm/iommu.c
> index 80fd3ad..37ca71e 100644
> --- a/virt/kvm/iommu.c
> +++ b/virt/kvm/iommu.c
> @@ -78,7 +78,7 @@ static int kvm_iommu_map_memslots(struct kvm *kvm)
> int i, r = 0;
> struct kvm_memslots *slots;
>
> - slots = rcu_dereference(kvm->memslots);
> + slots = kvm_memslots(kvm);
>
> for (i = 0; i < slots->nmemslots; i++) {
> r = kvm_iommu_map_pages(kvm, &slots->memslots[i]);
> @@ -217,7 +217,7 @@ static int kvm_iommu_unmap_memslots(struct kvm *kvm)
> int i;
> struct kvm_memslots *slots;
>
> - slots = rcu_dereference(kvm->memslots);
> + slots = kvm_memslots(kvm);
>
> for (i = 0; i < slots->nmemslots; i++) {
> kvm_iommu_put_pages(kvm, slots->memslots[i].base_gfn,
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index b03f863..58b2147 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -829,7 +829,7 @@ EXPORT_SYMBOL_GPL(kvm_is_error_hva);
> struct kvm_memory_slot *gfn_to_memslot_unaliased(struct kvm *kvm, gfn_t gfn)
> {
> int i;
> - struct kvm_memslots *slots = rcu_dereference(kvm->memslots);
> + struct kvm_memslots *slots = kvm_memslots(kvm);
>
> for (i = 0; i < slots->nmemslots; ++i) {
> struct kvm_memory_slot *memslot = &slots->memslots[i];
> @@ -851,7 +851,7 @@ struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
> int kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn)
> {
> int i;
> - struct kvm_memslots *slots = rcu_dereference(kvm->memslots);
> + struct kvm_memslots *slots = kvm_memslots(kvm);
>
> gfn = unalias_gfn_instantiation(kvm, gfn);
> for (i = 0; i < KVM_MEMORY_SLOTS; ++i) {
> @@ -895,7 +895,7 @@ out:
> int memslot_id(struct kvm *kvm, gfn_t gfn)
> {
> int i;
> - struct kvm_memslots *slots = rcu_dereference(kvm->memslots);
> + struct kvm_memslots *slots = kvm_memslots(kvm);
> struct kvm_memory_slot *memslot = NULL;
>
> gfn = unalias_gfn(kvm, gfn);
> @@ -1979,7 +1979,9 @@ int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
> int len, const void *val)
> {
> int i;
> - struct kvm_io_bus *bus = rcu_dereference(kvm->buses[bus_idx]);
> + struct kvm_io_bus *bus;
> +
> + bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu);
> for (i = 0; i < bus->dev_count; i++)
> if (!kvm_iodevice_write(bus->devs[i], addr, len, val))
> return 0;
> @@ -1991,8 +1993,9 @@ int kvm_io_bus_read(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
> int len, void *val)
> {
> int i;
> - struct kvm_io_bus *bus = rcu_dereference(kvm->buses[bus_idx]);
> + struct kvm_io_bus *bus;
>
> + bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu);
> for (i = 0; i < bus->dev_count; i++)
> if (!kvm_iodevice_read(bus->devs[i], addr, len, val))
> return 0;
>
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