Re: [PATCH kernel v2 2/6] KVM: PPC: Use RCU for arch.spapr_tce_tables
From: David Gibson <hidden>
Date: 2016-01-24 23:45:52
Also in:
kvm
On Thu, Jan 21, 2016 at 06:39:33PM +1100, Alexey Kardashevskiy wrote:
At the moment spapr_tce_tables is not protected against races.
That's not really true - it's protected by the kvm->lock mutex.
This makes use of RCU-variants of list helpers. As some bits are executed in real mode, this makes use of just introduced list_for_each_entry_rcu_notrace(). This converts release_spapr_tce_table() to a RCU scheduled handler.
The change itself is fine, though.
quoted hunk ↗ jump to hunk
Signed-off-by: Alexey Kardashevskiy <redacted> Reviewed-by: David Gibson <redacted> --- arch/powerpc/include/asm/kvm_host.h | 1 + arch/powerpc/kvm/book3s.c | 2 +- arch/powerpc/kvm/book3s_64_vio.c | 20 +++++++++++--------- 3 files changed, 13 insertions(+), 10 deletions(-)diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h index 271fefb..c7ee696 100644 --- a/arch/powerpc/include/asm/kvm_host.h +++ b/arch/powerpc/include/asm/kvm_host.h@@ -184,6 +184,7 @@ struct kvmppc_spapr_tce_table { struct kvm *kvm; u64 liobn; u32 window_size; + struct rcu_head rcu; struct page *pages[0]; };diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c index 638c6d9..b34220d 100644 --- a/arch/powerpc/kvm/book3s.c +++ b/arch/powerpc/kvm/book3s.c@@ -807,7 +807,7 @@ int kvmppc_core_init_vm(struct kvm *kvm) { #ifdef CONFIG_PPC64 - INIT_LIST_HEAD(&kvm->arch.spapr_tce_tables); + INIT_LIST_HEAD_RCU(&kvm->arch.spapr_tce_tables); INIT_LIST_HEAD(&kvm->arch.rtas_tokens); #endifdiff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c index 54cf9bc..9526c34 100644 --- a/arch/powerpc/kvm/book3s_64_vio.c +++ b/arch/powerpc/kvm/book3s_64_vio.c@@ -45,19 +45,16 @@ static long kvmppc_stt_npages(unsigned long window_size) * sizeof(u64), PAGE_SIZE) / PAGE_SIZE; } -static void release_spapr_tce_table(struct kvmppc_spapr_tce_table *stt) +static void release_spapr_tce_table(struct rcu_head *head) { - struct kvm *kvm = stt->kvm; + struct kvmppc_spapr_tce_table *stt = container_of(head, + struct kvmppc_spapr_tce_table, rcu); int i; - mutex_lock(&kvm->lock); - list_del(&stt->list); for (i = 0; i < kvmppc_stt_npages(stt->window_size); i++) __free_page(stt->pages[i]); + kfree(stt); - mutex_unlock(&kvm->lock); - - kvm_put_kvm(kvm); } static int kvm_spapr_tce_fault(struct vm_area_struct *vma, struct vm_fault *vmf)@@ -88,7 +85,12 @@ static int kvm_spapr_tce_release(struct inode *inode, struct file *filp) { struct kvmppc_spapr_tce_table *stt = filp->private_data; - release_spapr_tce_table(stt); + list_del_rcu(&stt->list); + + kvm_put_kvm(stt->kvm); + + call_rcu(&stt->rcu, release_spapr_tce_table); + return 0; }@@ -131,7 +133,7 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm, kvm_get_kvm(kvm); mutex_lock(&kvm->lock); - list_add(&stt->list, &kvm->arch.spapr_tce_tables); + list_add_rcu(&stt->list, &kvm->arch.spapr_tce_tables); mutex_unlock(&kvm->lock);
-- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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