From: Vitaly Kuznetsov vkuznets@redhat.com
[ Upstream commit 87ee613d076351950b74383215437f841ebbeb75 ]
In most common cases VP index of a vcpu matches its vcpu index. Userspace is, however, free to set any mapping it wishes and we need to account for that when we need to find a vCPU with a particular VP index. To keep search algorithms optimal in both cases introduce 'num_mismatched_vp_indexes' counter showing how many vCPUs with mismatching VP index we have. In case the counter is zero we can assume vp_index == vcpu_idx.
Signed-off-by: Vitaly Kuznetsov vkuznets@redhat.com Reviewed-by: Roman Kagan rkagan@virtuozzo.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/include/asm/kvm_host.h | 3 +++ arch/x86/kvm/hyperv.c | 26 +++++++++++++++++++++++--- 2 files changed, 26 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 3245b95ad2d97..b6417454a9d79 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -784,6 +784,9 @@ struct kvm_hv { u64 hv_reenlightenment_control; u64 hv_tsc_emulation_control; u64 hv_tsc_emulation_status; + + /* How many vCPUs have VP index != vCPU index */ + atomic_t num_mismatched_vp_indexes; };
enum kvm_irqchip_mode { diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index 3f2775aac5545..2bb554b90b3c2 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -1045,11 +1045,31 @@ static int kvm_hv_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host) struct kvm_vcpu_hv *hv_vcpu = &vcpu->arch.hyperv;
switch (msr) { - case HV_X64_MSR_VP_INDEX: - if (!host || (u32)data >= KVM_MAX_VCPUS) + case HV_X64_MSR_VP_INDEX: { + struct kvm_hv *hv = &vcpu->kvm->arch.hyperv; + int vcpu_idx = kvm_vcpu_get_idx(vcpu); + u32 new_vp_index = (u32)data; + + if (!host || new_vp_index >= KVM_MAX_VCPUS) return 1; - hv_vcpu->vp_index = (u32)data; + + if (new_vp_index == hv_vcpu->vp_index) + return 0; + + /* + * The VP index is initialized to vcpu_index by + * kvm_hv_vcpu_postcreate so they initially match. Now the + * VP index is changing, adjust num_mismatched_vp_indexes if + * it now matches or no longer matches vcpu_idx. + */ + if (hv_vcpu->vp_index == vcpu_idx) + atomic_inc(&hv->num_mismatched_vp_indexes); + else if (new_vp_index == vcpu_idx) + atomic_dec(&hv->num_mismatched_vp_indexes); + + hv_vcpu->vp_index = new_vp_index; break; + } case HV_X64_MSR_VP_ASSIST_PAGE: { u64 gfn; unsigned long addr;