On 10.10.24 10:57, Vitaly Kuznetsov wrote:
Nikolas Wipper nikwip@amazon.de writes:
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 46e0a466d7fb..7571ac578884 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -695,6 +695,9 @@ struct kvm_vcpu_hv { u64 vm_id; u32 vp_id; } nested;
- bool suspended;
- int waiting_on;
I don't quite understand why we need 'suspended' at all. Isn't it always suspended when 'waiting_on != -1'? I can see we always update these two in pair.
This is mainly for future proofing the implementation. You are right, this is currently not required, but it's nice to have a single flags, so that when the suspended state is used in a different context, the whole logic surrounding it still works.
Also, I would suggest we use a more descriptive name. 'waiting_on_vcpu_id', for example.
Sounds good.
};
struct kvm_hypervisor_cpuid { diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index 4f0a94346d00..6e7941ed25ae 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -971,6 +971,7 @@ int kvm_hv_vcpu_init(struct kvm_vcpu *vcpu)
vcpu->arch.hyperv = hv_vcpu; hv_vcpu->vcpu = vcpu;
hv_vcpu->waiting_on = -1;
synic_init(&hv_vcpu->synic);
@@ -2915,3 +2916,32 @@ int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
return 0; }
+void kvm_hv_vcpu_suspend_tlb_flush(struct kvm_vcpu *vcpu, int vcpu_id)
Can we make parameter's name 'waiting_on_vcpu_id' as well? Because as-is I'm getting confused which CPU of these two is actually getting suspended)
Yup, that would certainly help readability.
Also, why do we need '_tlb_flush' in the name? The mechanism seems to be fairly generic, it's just that we use it for TLB flushes.
The 'waiting_on' part is TLB flushing specific.
+{
- /* waiting_on's store should happen before suspended's */
- WRITE_ONCE(vcpu->arch.hyperv->waiting_on, vcpu_id);
- WRITE_ONCE(vcpu->arch.hyperv->suspended, true);
+}
+void kvm_hv_vcpu_unsuspend_tlb_flush(struct kvm_vcpu *vcpu)
And here someone may expect this means 'unsuspend vcpu' but in reality this means 'unsuspend all vCPUs which are waiting on 'vcpu'). I guess we need a rename. How about
void kvm_hv_unsuspend_vcpus(struct kvm_vcpu *waiting_on_vcpu)
?
Also sounds good.
+{
- DECLARE_BITMAP(vcpu_mask, KVM_MAX_VCPUS);
- struct kvm_vcpu_hv *vcpu_hv;
- struct kvm_vcpu *v;
- unsigned long i;
- kvm_for_each_vcpu(i, v, vcpu->kvm) {
vcpu_hv = to_hv_vcpu(v);if (kvm_hv_vcpu_suspended(v) &&READ_ONCE(vcpu_hv->waiting_on) == vcpu->vcpu_id) {/* waiting_on's store should happen before suspended's */WRITE_ONCE(v->arch.hyperv->waiting_on, -1);WRITE_ONCE(v->arch.hyperv->suspended, false);__set_bit(i, vcpu_mask);}- }
- kvm_make_vcpus_request_mask(vcpu->kvm, KVM_REQ_EVENT, vcpu_mask);
+} diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h index 913bfc96959c..a55832cea221 100644 --- a/arch/x86/kvm/hyperv.h +++ b/arch/x86/kvm/hyperv.h @@ -265,6 +265,15 @@ static inline void kvm_hv_nested_transtion_tlb_flush(struct kvm_vcpu *vcpu, }
int kvm_hv_vcpu_flush_tlb(struct kvm_vcpu *vcpu);
+static inline bool kvm_hv_vcpu_suspended(struct kvm_vcpu *vcpu) +{
- return vcpu->arch.hyperv_enabled &&
READ_ONCE(vcpu->arch.hyperv->suspended);I don't think READ_ONCE() means anything here, does it?
It does prevent compiler optimisations and is actually required[1]. Also it makes clear that this variable is shared, and may be accessed from remote CPUs.
[1] https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0124r6.html#Variab...
Nikolas