Messages in this thread | | | Subject | Re: [PATCH 1/1] KVM: s390: index kvm->arch.idle_mask by vcpu_idx | From | Christian Borntraeger <> | Date | Fri, 27 Aug 2021 18:36:48 +0200 |
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On 27.08.21 16:06, Claudio Imbrenda wrote: > On Fri, 27 Aug 2021 14:54:29 +0200 > Halil Pasic <pasic@linux.ibm.com> wrote: > >> While in practice vcpu->vcpu_idx == vcpu->vcp_id is often true, >> it may not always be, and we must not rely on this. > > why? > > maybe add a simple explanation of why vcpu_idx and vcpu_id can be > different, namely: > KVM decides the vcpu_idx, userspace decides the vcpu_id, thus the two > might not match > >> >> Currently kvm->arch.idle_mask is indexed by vcpu_id, which implies >> that code like >> for_each_set_bit(vcpu_id, kvm->arch.idle_mask, online_vcpus) { >> vcpu = kvm_get_vcpu(kvm, vcpu_id); > > you can also add a sentence to clarify that kvm_get_vcpu expects an > vcpu_idx, not an vcpu_id. > >> do_stuff(vcpu);
I will modify the patch description accordingly before sending to Paolo. Thanks for noticing.
>> } >> is not legit. The trouble is, we do actually use kvm->arch.idle_mask >> like this. To fix this problem we have two options. Either use >> kvm_get_vcpu_by_id(vcpu_id), which would loop to find the right vcpu_id, >> or switch to indexing via vcpu_idx. The latter is preferable for obvious >> reasons. >> >> Let us make switch from indexing kvm->arch.idle_mask by vcpu_id to >> indexing it by vcpu_idx. To keep gisa_int.kicked_mask indexed by the >> same index as idle_mask lets make the same change for it as well. >> >> Signed-off-by: Halil Pasic <pasic@linux.ibm.com> >> Fixes: 1ee0bc559dc3 ("KVM: s390: get rid of local_int array") > > otherwise looks good to me. > > Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com> > >> Cc: <stable@vger.kernel.org> # 3.15+ >> --- >> arch/s390/include/asm/kvm_host.h | 1 + >> arch/s390/kvm/interrupt.c | 12 ++++++------ >> arch/s390/kvm/kvm-s390.c | 2 +- >> arch/s390/kvm/kvm-s390.h | 2 +- >> 4 files changed, 9 insertions(+), 8 deletions(-) >> >> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h >> index 161a9e12bfb8..630eab0fa176 100644 >> --- a/arch/s390/include/asm/kvm_host.h >> +++ b/arch/s390/include/asm/kvm_host.h >> @@ -957,6 +957,7 @@ struct kvm_arch{ >> atomic64_t cmma_dirty_pages; >> /* subset of available cpu features enabled by user space */ >> DECLARE_BITMAP(cpu_feat, KVM_S390_VM_CPU_FEAT_NR_BITS); >> + /* indexed by vcpu_idx */ >> DECLARE_BITMAP(idle_mask, KVM_MAX_VCPUS); >> struct kvm_s390_gisa_interrupt gisa_int; >> struct kvm_s390_pv pv; >> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c >> index d548d60caed2..16256e17a544 100644 >> --- a/arch/s390/kvm/interrupt.c >> +++ b/arch/s390/kvm/interrupt.c >> @@ -419,13 +419,13 @@ static unsigned long deliverable_irqs(struct kvm_vcpu *vcpu) >> static void __set_cpu_idle(struct kvm_vcpu *vcpu) >> { >> kvm_s390_set_cpuflags(vcpu, CPUSTAT_WAIT); >> - set_bit(vcpu->vcpu_id, vcpu->kvm->arch.idle_mask); >> + set_bit(kvm_vcpu_get_idx(vcpu), vcpu->kvm->arch.idle_mask); >> } >> >> static void __unset_cpu_idle(struct kvm_vcpu *vcpu) >> { >> kvm_s390_clear_cpuflags(vcpu, CPUSTAT_WAIT); >> - clear_bit(vcpu->vcpu_id, vcpu->kvm->arch.idle_mask); >> + clear_bit(kvm_vcpu_get_idx(vcpu), vcpu->kvm->arch.idle_mask); >> } >> >> static void __reset_intercept_indicators(struct kvm_vcpu *vcpu) >> @@ -3050,18 +3050,18 @@ int kvm_s390_get_irq_state(struct kvm_vcpu *vcpu, __u8 __user *buf, int len) >> >> static void __airqs_kick_single_vcpu(struct kvm *kvm, u8 deliverable_mask) >> { >> - int vcpu_id, online_vcpus = atomic_read(&kvm->online_vcpus); >> + int vcpu_idx, online_vcpus = atomic_read(&kvm->online_vcpus); >> struct kvm_s390_gisa_interrupt *gi = &kvm->arch.gisa_int; >> struct kvm_vcpu *vcpu; >> >> - for_each_set_bit(vcpu_id, kvm->arch.idle_mask, online_vcpus) { >> - vcpu = kvm_get_vcpu(kvm, vcpu_id); >> + for_each_set_bit(vcpu_idx, kvm->arch.idle_mask, online_vcpus) { >> + vcpu = kvm_get_vcpu(kvm, vcpu_idx); >> if (psw_ioint_disabled(vcpu)) >> continue; >> deliverable_mask &= (u8)(vcpu->arch.sie_block->gcr[6] >> 24); >> if (deliverable_mask) { >> /* lately kicked but not yet running */ >> - if (test_and_set_bit(vcpu_id, gi->kicked_mask)) >> + if (test_and_set_bit(vcpu_idx, gi->kicked_mask)) >> return; >> kvm_s390_vcpu_wakeup(vcpu); >> return; >> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c >> index 4527ac7b5961..8580543c5bc3 100644 >> --- a/arch/s390/kvm/kvm-s390.c >> +++ b/arch/s390/kvm/kvm-s390.c >> @@ -4044,7 +4044,7 @@ static int vcpu_pre_run(struct kvm_vcpu *vcpu) >> kvm_s390_patch_guest_per_regs(vcpu); >> } >> >> - clear_bit(vcpu->vcpu_id, vcpu->kvm->arch.gisa_int.kicked_mask); >> + clear_bit(kvm_vcpu_get_idx(vcpu), vcpu->kvm->arch.gisa_int.kicked_mask); >> >> vcpu->arch.sie_block->icptcode = 0; >> cpuflags = atomic_read(&vcpu->arch.sie_block->cpuflags); >> diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h >> index 9fad25109b0d..ecd741ee3276 100644 >> --- a/arch/s390/kvm/kvm-s390.h >> +++ b/arch/s390/kvm/kvm-s390.h >> @@ -79,7 +79,7 @@ static inline int is_vcpu_stopped(struct kvm_vcpu *vcpu) >> >> static inline int is_vcpu_idle(struct kvm_vcpu *vcpu) >> { >> - return test_bit(vcpu->vcpu_id, vcpu->kvm->arch.idle_mask); >> + return test_bit(kvm_vcpu_get_idx(vcpu), vcpu->kvm->arch.idle_mask); >> } >> >> static inline int kvm_is_ucontrol(struct kvm *kvm) >> >> base-commit: 77dd11439b86e3f7990e4c0c9e0b67dca82750ba >
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