From: Paul Mackerras <paulus@samba.org> To: Alexander Graf <agraf@suse.de> Cc: kvm-ppc@vger.kernel.org, kvm@vger.kernel.org Subject: [PATCH 07/12] KVM: PPC: Book3S HV: Fix some races in starting secondary threads Date: Tue, 28 Aug 2012 22:36:21 +1000 [thread overview] Message-ID: <20120828123621.GH7258@bloggs.ozlabs.ibm.com> (raw) In-Reply-To: <20120828123043.GA7258@bloggs.ozlabs.ibm.com> Subsequent patches implementing in-kernel XICS emulation will make it possible for IPIs to arrive at secondary threads at arbitrary times. This fixes some races in how we start the secondary threads, which if not fixed could lead to occasional crashes of the host kernel. This makes sure that (a) we have grabbed all the secondary threads, and verified that they are no longer in the kernel, before we start any thread, (b) that the secondary thread loads its vcpu pointer after clearing the IPI that woke it up (so we don't miss a wakeup), and (c) that the secondary thread clears its vcpu pointer before incrementing the nap count. It also removes unnecessary setting of the vcpu and vcore pointers in the paca in kvmppc_core_vcpu_load. Signed-off-by: Paul Mackerras <paulus@samba.org> --- arch/powerpc/kvm/book3s_hv.c | 41 ++++++++++++++++++------------- arch/powerpc/kvm/book3s_hv_rmhandlers.S | 11 ++++++--- 2 files changed, 32 insertions(+), 20 deletions(-) diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index e6d8579..2d0477a 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -64,8 +64,6 @@ void kvmppc_core_vcpu_load(struct kvm_vcpu *vcpu, int cpu) { struct kvmppc_vcore *vc = vcpu->arch.vcore; - local_paca->kvm_hstate.kvm_vcpu = vcpu; - local_paca->kvm_hstate.kvm_vcore = vc; if (vc->runner == vcpu && vc->vcore_state != VCORE_INACTIVE) vc->stolen_tb += mftb() - vc->preempt_tb; } @@ -776,6 +774,7 @@ static int kvmppc_grab_hwthread(int cpu) /* Ensure the thread won't go into the kernel if it wakes */ tpaca->kvm_hstate.hwthread_req = 1; + tpaca->kvm_hstate.kvm_vcpu = NULL; /* * If the thread is already executing in the kernel (e.g. handling @@ -825,7 +824,6 @@ static void kvmppc_start_thread(struct kvm_vcpu *vcpu) smp_wmb(); #if defined(CONFIG_PPC_ICP_NATIVE) && defined(CONFIG_SMP) if (vcpu->arch.ptid) { - kvmppc_grab_hwthread(cpu); xics_wake_cpu(cpu); ++vc->n_woken; } @@ -851,7 +849,8 @@ static void kvmppc_wait_for_nap(struct kvmppc_vcore *vc) /* * Check that we are on thread 0 and that any other threads in - * this core are off-line. + * this core are off-line. Then grab the threads so they can't + * enter the kernel. */ static int on_primary_thread(void) { @@ -863,6 +862,17 @@ static int on_primary_thread(void) while (++thr < threads_per_core) if (cpu_online(cpu + thr)) return 0; + + /* Grab all hw threads so they can't go into the kernel */ + for (thr = 1; thr < threads_per_core; ++thr) { + if (kvmppc_grab_hwthread(cpu + thr)) { + /* Couldn't grab one; let the others go */ + do { + kvmppc_release_hwthread(cpu + thr); + } while (--thr > 0); + return 0; + } + } return 1; } @@ -911,16 +921,6 @@ static int kvmppc_run_core(struct kvmppc_vcore *vc) } /* - * Make sure we are running on thread 0, and that - * secondary threads are offline. - */ - if (threads_per_core > 1 && !on_primary_thread()) { - list_for_each_entry(vcpu, &vc->runnable_threads, arch.run_list) - vcpu->arch.ret = -EBUSY; - goto out; - } - - /* * Assign physical thread IDs, first to non-ceded vcpus * and then to ceded ones. */ @@ -939,15 +939,22 @@ static int kvmppc_run_core(struct kvmppc_vcore *vc) if (vcpu->arch.ceded) vcpu->arch.ptid = ptid++; + /* + * Make sure we are running on thread 0, and that + * secondary threads are offline. + */ + if (threads_per_core > 1 && !on_primary_thread()) { + list_for_each_entry(vcpu, &vc->runnable_threads, arch.run_list) + vcpu->arch.ret = -EBUSY; + goto out; + } + vc->stolen_tb += mftb() - vc->preempt_tb; vc->pcpu = smp_processor_id(); list_for_each_entry(vcpu, &vc->runnable_threads, arch.run_list) { kvmppc_start_thread(vcpu); kvmppc_create_dtl_entry(vcpu, vc); } - /* Grab any remaining hw threads so they can't go into the kernel */ - for (i = ptid; i < threads_per_core; ++i) - kvmppc_grab_hwthread(vc->pcpu + i); preempt_disable(); spin_unlock(&vc->lock); diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S index 44b72fe..1e90ef6 100644 --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S @@ -134,8 +134,11 @@ kvm_start_guest: 27: /* XXX should handle hypervisor maintenance interrupts etc. here */ + /* reload vcpu pointer after clearing the IPI */ + ld r4,HSTATE_KVM_VCPU(r13) + cmpdi r4,0 /* if we have no vcpu to run, go back to sleep */ - beq cr1,kvm_no_guest + beq kvm_no_guest /* were we napping due to cede? */ lbz r0,HSTATE_NAPPING(r13) @@ -1587,6 +1590,10 @@ secondary_too_late: .endr secondary_nap: + /* Clear our vcpu pointer so we don't come back in early */ + li r0, 0 + std r0, HSTATE_KVM_VCPU(r13) + lwsync /* Clear any pending IPI - assume we're a secondary thread */ ld r5, HSTATE_XICS_PHYS(r13) li r7, XICS_XIRR @@ -1612,8 +1619,6 @@ secondary_nap: kvm_no_guest: li r0, KVM_HWTHREAD_IN_NAP stb r0, HSTATE_HWTHREAD_STATE(r13) - li r0, 0 - std r0, HSTATE_KVM_VCPU(r13) li r3, LPCR_PECE0 mfspr r4, SPRN_LPCR -- 1.7.10.rc3.219.g53414
WARNING: multiple messages have this Message-ID (diff)
From: Paul Mackerras <paulus@samba.org> To: Alexander Graf <agraf@suse.de> Cc: kvm-ppc@vger.kernel.org, kvm@vger.kernel.org Subject: [PATCH 07/12] KVM: PPC: Book3S HV: Fix some races in starting secondary threads Date: Tue, 28 Aug 2012 12:36:21 +0000 [thread overview] Message-ID: <20120828123621.GH7258@bloggs.ozlabs.ibm.com> (raw) In-Reply-To: <20120828123043.GA7258@bloggs.ozlabs.ibm.com> Subsequent patches implementing in-kernel XICS emulation will make it possible for IPIs to arrive at secondary threads at arbitrary times. This fixes some races in how we start the secondary threads, which if not fixed could lead to occasional crashes of the host kernel. This makes sure that (a) we have grabbed all the secondary threads, and verified that they are no longer in the kernel, before we start any thread, (b) that the secondary thread loads its vcpu pointer after clearing the IPI that woke it up (so we don't miss a wakeup), and (c) that the secondary thread clears its vcpu pointer before incrementing the nap count. It also removes unnecessary setting of the vcpu and vcore pointers in the paca in kvmppc_core_vcpu_load. Signed-off-by: Paul Mackerras <paulus@samba.org> --- arch/powerpc/kvm/book3s_hv.c | 41 ++++++++++++++++++------------- arch/powerpc/kvm/book3s_hv_rmhandlers.S | 11 ++++++--- 2 files changed, 32 insertions(+), 20 deletions(-) diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index e6d8579..2d0477a 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -64,8 +64,6 @@ void kvmppc_core_vcpu_load(struct kvm_vcpu *vcpu, int cpu) { struct kvmppc_vcore *vc = vcpu->arch.vcore; - local_paca->kvm_hstate.kvm_vcpu = vcpu; - local_paca->kvm_hstate.kvm_vcore = vc; if (vc->runner = vcpu && vc->vcore_state != VCORE_INACTIVE) vc->stolen_tb += mftb() - vc->preempt_tb; } @@ -776,6 +774,7 @@ static int kvmppc_grab_hwthread(int cpu) /* Ensure the thread won't go into the kernel if it wakes */ tpaca->kvm_hstate.hwthread_req = 1; + tpaca->kvm_hstate.kvm_vcpu = NULL; /* * If the thread is already executing in the kernel (e.g. handling @@ -825,7 +824,6 @@ static void kvmppc_start_thread(struct kvm_vcpu *vcpu) smp_wmb(); #if defined(CONFIG_PPC_ICP_NATIVE) && defined(CONFIG_SMP) if (vcpu->arch.ptid) { - kvmppc_grab_hwthread(cpu); xics_wake_cpu(cpu); ++vc->n_woken; } @@ -851,7 +849,8 @@ static void kvmppc_wait_for_nap(struct kvmppc_vcore *vc) /* * Check that we are on thread 0 and that any other threads in - * this core are off-line. + * this core are off-line. Then grab the threads so they can't + * enter the kernel. */ static int on_primary_thread(void) { @@ -863,6 +862,17 @@ static int on_primary_thread(void) while (++thr < threads_per_core) if (cpu_online(cpu + thr)) return 0; + + /* Grab all hw threads so they can't go into the kernel */ + for (thr = 1; thr < threads_per_core; ++thr) { + if (kvmppc_grab_hwthread(cpu + thr)) { + /* Couldn't grab one; let the others go */ + do { + kvmppc_release_hwthread(cpu + thr); + } while (--thr > 0); + return 0; + } + } return 1; } @@ -911,16 +921,6 @@ static int kvmppc_run_core(struct kvmppc_vcore *vc) } /* - * Make sure we are running on thread 0, and that - * secondary threads are offline. - */ - if (threads_per_core > 1 && !on_primary_thread()) { - list_for_each_entry(vcpu, &vc->runnable_threads, arch.run_list) - vcpu->arch.ret = -EBUSY; - goto out; - } - - /* * Assign physical thread IDs, first to non-ceded vcpus * and then to ceded ones. */ @@ -939,15 +939,22 @@ static int kvmppc_run_core(struct kvmppc_vcore *vc) if (vcpu->arch.ceded) vcpu->arch.ptid = ptid++; + /* + * Make sure we are running on thread 0, and that + * secondary threads are offline. + */ + if (threads_per_core > 1 && !on_primary_thread()) { + list_for_each_entry(vcpu, &vc->runnable_threads, arch.run_list) + vcpu->arch.ret = -EBUSY; + goto out; + } + vc->stolen_tb += mftb() - vc->preempt_tb; vc->pcpu = smp_processor_id(); list_for_each_entry(vcpu, &vc->runnable_threads, arch.run_list) { kvmppc_start_thread(vcpu); kvmppc_create_dtl_entry(vcpu, vc); } - /* Grab any remaining hw threads so they can't go into the kernel */ - for (i = ptid; i < threads_per_core; ++i) - kvmppc_grab_hwthread(vc->pcpu + i); preempt_disable(); spin_unlock(&vc->lock); diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S index 44b72fe..1e90ef6 100644 --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S @@ -134,8 +134,11 @@ kvm_start_guest: 27: /* XXX should handle hypervisor maintenance interrupts etc. here */ + /* reload vcpu pointer after clearing the IPI */ + ld r4,HSTATE_KVM_VCPU(r13) + cmpdi r4,0 /* if we have no vcpu to run, go back to sleep */ - beq cr1,kvm_no_guest + beq kvm_no_guest /* were we napping due to cede? */ lbz r0,HSTATE_NAPPING(r13) @@ -1587,6 +1590,10 @@ secondary_too_late: .endr secondary_nap: + /* Clear our vcpu pointer so we don't come back in early */ + li r0, 0 + std r0, HSTATE_KVM_VCPU(r13) + lwsync /* Clear any pending IPI - assume we're a secondary thread */ ld r5, HSTATE_XICS_PHYS(r13) li r7, XICS_XIRR @@ -1612,8 +1619,6 @@ secondary_nap: kvm_no_guest: li r0, KVM_HWTHREAD_IN_NAP stb r0, HSTATE_HWTHREAD_STATE(r13) - li r0, 0 - std r0, HSTATE_KVM_VCPU(r13) li r3, LPCR_PECE0 mfspr r4, SPRN_LPCR -- 1.7.10.rc3.219.g53414
next prev parent reply other threads:[~2012-08-28 12:42 UTC|newest] Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-08-28 12:30 [PATCH 0/12] Sundry fixes for Book3S HV Paul Mackerras 2012-08-28 12:30 ` Paul Mackerras 2012-08-28 12:32 ` [PATCH 01/12] KVM: PPC: Move kvm->arch.slot_phys into memslot.arch Paul Mackerras 2012-08-28 12:32 ` Paul Mackerras 2012-08-28 12:32 ` [PATCH 02/12] KVM: PPC: Book3S HV: Take the SRCU read lock before looking up memslots Paul Mackerras 2012-08-28 12:32 ` Paul Mackerras 2012-08-28 12:33 ` [PATCH 03/12] KVM: PPC: Book3S HV: Provide a way for userspace to get/set per-vCPU areas Paul Mackerras 2012-08-28 12:33 ` Paul Mackerras 2012-08-28 12:34 ` [PATCH 04/12] KVM: PPC: Book3S HV: Allow KVM guests to stop secondary threads coming online Paul Mackerras 2012-08-28 12:34 ` Paul Mackerras 2012-08-29 4:51 ` [PATCH v2 " Paul Mackerras 2012-08-29 4:51 ` Paul Mackerras 2012-08-28 12:34 ` [PATCH 05/12] KVM: PPC: Fix updates of vcpu->cpu on HV KVM Paul Mackerras 2012-08-28 12:34 ` Paul Mackerras 2012-08-28 12:35 ` [PATCH 06/12] KVM: PPC: Book3S HV: Remove bogus update of thread IDs in " Paul Mackerras 2012-08-28 12:35 ` Paul Mackerras 2012-08-28 12:36 ` Paul Mackerras [this message] 2012-08-28 12:36 ` [PATCH 07/12] KVM: PPC: Book3S HV: Fix some races in starting secondary threads Paul Mackerras 2012-08-28 12:37 ` [PATCH 08/12] KVM: PPC: Book3s HV: Don't access runnable threads list without vcore lock Paul Mackerras 2012-08-28 12:37 ` Paul Mackerras 2012-08-28 12:38 ` [PATCH 09/12] KVM: PPC: Book3S HV: Fixes for late-joining threads Paul Mackerras 2012-08-28 12:38 ` Paul Mackerras 2012-08-28 12:39 ` [PATCH 10/12] KVM: PPC: Book3S HV: Run virtual core whenever any vcpus in it can run Paul Mackerras 2012-08-28 12:39 ` Paul Mackerras 2012-08-28 12:40 ` [PATCH 11/12] KVM: PPC: Book3S HV: Fix accounting of stolen time Paul Mackerras 2012-08-28 12:40 ` Paul Mackerras 2012-08-28 12:40 ` [PATCH 12/12] KVM: PPC: Book3S HV: Fix calculation of guest phys address for MMIO emulation Paul Mackerras 2012-08-28 12:40 ` Paul Mackerras
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