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 (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