Hi Halil,
Dne 27. 08. 21 v 14:54 Halil Pasic napsal(a):
While in practice vcpu->vcpu_idx == vcpu->vcp_id is often true,
it may not always be, and we must not rely on this.
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);
do_stuff(vcpu);
}
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.
I'm just backporting this fix to SLES 12 SP5, and I've noticed that
there is still this code in __floating_irq_kick():
/* find idle VCPUs first, then round robin */
sigcpu = find_first_bit(fi->idle_mask, online_vcpus);
/* ... round robin loop removed ...
dst_vcpu = kvm_get_vcpu(kvm, sigcpu);
It seems to me that this does exactly the thing that is not legit, but
I'm no expert. Did I miss something?
Petr T
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@xxxxxxxxxxxxx>
Fixes: 1ee0bc559dc3 ("KVM: s390: get rid of local_int array")
Cc: <stable@xxxxxxxxxxxxxxx> # 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
