From 0823570f01989d3703751f66534a138d4fae062e Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov Date: Tue, 1 Nov 2022 15:53:47 +0100 Subject: [PATCH] KVM: x86: hyper-v: Introduce TLB flush fifo To allow flushing individual GVAs instead of always flushing the whole VPID a per-vCPU structure to pass the requests is needed. Use standard 'kfifo' to queue two types of entries: individual GVA (GFN + up to 4095 following GFNs in the lower 12 bits) and 'flush all'. The size of the fifo is arbitrarily set to '16'. Note, kvm_hv_flush_tlb() only queues 'flush all' entries for now and kvm_hv_vcpu_flush_tlb() doesn't actually read the fifo just resets the queue before returning -EOPNOTSUPP (which triggers full TLB flush) so the functional change is very small but the infrastructure is prepared to handle individual GVA flush requests. Reviewed-by: Sean Christopherson Signed-off-by: Vitaly Kuznetsov Signed-off-by: Paolo Bonzini Message-Id: <20221101145426.251680-10-vkuznets@redhat.com> Signed-off-by: Paolo Bonzini --- arch/x86/include/asm/kvm_host.h | 20 ++++++++++++++ arch/x86/kvm/hyperv.c | 47 +++++++++++++++++++++++++++++++++ arch/x86/kvm/hyperv.h | 15 +++++++++++ arch/x86/kvm/svm/svm.c | 2 +- arch/x86/kvm/x86.c | 11 ++++++-- 5 files changed, 92 insertions(+), 3 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 0b85230a0e0a..3e35dcf40dc7 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -25,6 +25,7 @@ #include #include #include +#include #include #include @@ -618,6 +619,23 @@ struct kvm_vcpu_hv_synic { bool dont_zero_synic_pages; }; +/* The maximum number of entries on the TLB flush fifo. */ +#define KVM_HV_TLB_FLUSH_FIFO_SIZE (16) +/* + * Note: the following 'magic' entry is made up by KVM to avoid putting + * anything besides GVA on the TLB flush fifo. It is theoretically possible + * to observe a request to flush 4095 PFNs starting from 0xfffffffffffff000 + * which will look identical. KVM's action to 'flush everything' instead of + * flushing these particular addresses is, however, fully legitimate as + * flushing more than requested is always OK. + */ +#define KVM_HV_TLB_FLUSHALL_ENTRY ((u64)-1) + +struct kvm_vcpu_hv_tlb_flush_fifo { + spinlock_t write_lock; + DECLARE_KFIFO(entries, u64, KVM_HV_TLB_FLUSH_FIFO_SIZE); +}; + /* Hyper-V per vcpu emulation context */ struct kvm_vcpu_hv { struct kvm_vcpu *vcpu; @@ -639,6 +657,8 @@ struct kvm_vcpu_hv { u32 nested_eax; /* HYPERV_CPUID_NESTED_FEATURES.EAX */ u32 nested_ebx; /* HYPERV_CPUID_NESTED_FEATURES.EBX */ } cpuid_cache; + + struct kvm_vcpu_hv_tlb_flush_fifo tlb_flush_fifo; }; /* Xen HVM per vcpu emulation context */ diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index 3c0f639f6a05..9d9a5ff2d54b 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -29,6 +29,7 @@ #include #include #include +#include #include #include @@ -954,6 +955,9 @@ int kvm_hv_vcpu_init(struct kvm_vcpu *vcpu) hv_vcpu->vp_index = vcpu->vcpu_idx; + INIT_KFIFO(hv_vcpu->tlb_flush_fifo.entries); + spin_lock_init(&hv_vcpu->tlb_flush_fifo.write_lock); + return 0; } @@ -1783,6 +1787,37 @@ static u64 kvm_get_sparse_vp_set(struct kvm *kvm, struct kvm_hv_hcall *hc, var_cnt * sizeof(*sparse_banks)); } +static void hv_tlb_flush_enqueue(struct kvm_vcpu *vcpu) +{ + struct kvm_vcpu_hv_tlb_flush_fifo *tlb_flush_fifo; + struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu); + u64 flush_all_entry = KVM_HV_TLB_FLUSHALL_ENTRY; + + if (!hv_vcpu) + return; + + tlb_flush_fifo = &hv_vcpu->tlb_flush_fifo; + + kfifo_in_spinlocked_noirqsave(&tlb_flush_fifo->entries, &flush_all_entry, + 1, &tlb_flush_fifo->write_lock); +} + +int kvm_hv_vcpu_flush_tlb(struct kvm_vcpu *vcpu) +{ + struct kvm_vcpu_hv_tlb_flush_fifo *tlb_flush_fifo; + struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu); + + if (!hv_vcpu) + return -EINVAL; + + tlb_flush_fifo = &hv_vcpu->tlb_flush_fifo; + + kfifo_reset_out(&tlb_flush_fifo->entries); + + /* Precise flushing isn't implemented yet. */ + return -EOPNOTSUPP; +} + static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc) { struct kvm *kvm = vcpu->kvm; @@ -1791,6 +1826,8 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc) DECLARE_BITMAP(vcpu_mask, KVM_MAX_VCPUS); u64 valid_bank_mask; u64 sparse_banks[KVM_HV_MAX_SPARSE_VCPU_SET_BITS]; + struct kvm_vcpu *v; + unsigned long i; bool all_cpus; /* @@ -1870,10 +1907,20 @@ do_flush: * analyze it here, flush TLB regardless of the specified address space. */ if (all_cpus) { + kvm_for_each_vcpu(i, v, kvm) + hv_tlb_flush_enqueue(v); + kvm_make_all_cpus_request(kvm, KVM_REQ_HV_TLB_FLUSH); } else { sparse_set_to_vcpu_mask(kvm, sparse_banks, valid_bank_mask, vcpu_mask); + for_each_set_bit(i, vcpu_mask, KVM_MAX_VCPUS) { + v = kvm_get_vcpu(kvm, i); + if (!v) + continue; + hv_tlb_flush_enqueue(v); + } + kvm_make_vcpus_request_mask(kvm, KVM_REQ_HV_TLB_FLUSH, vcpu_mask); } diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h index 1030b1b50552..f79edf9234cd 100644 --- a/arch/x86/kvm/hyperv.h +++ b/arch/x86/kvm/hyperv.h @@ -151,4 +151,19 @@ int kvm_vm_ioctl_hv_eventfd(struct kvm *kvm, struct kvm_hyperv_eventfd *args); int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid, struct kvm_cpuid_entry2 __user *entries); +static inline void kvm_hv_vcpu_purge_flush_tlb(struct kvm_vcpu *vcpu) +{ + struct kvm_vcpu_hv_tlb_flush_fifo *tlb_flush_fifo; + struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu); + + if (!hv_vcpu || !kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu)) + return; + + tlb_flush_fifo = &hv_vcpu->tlb_flush_fifo; + + kfifo_reset_out(&tlb_flush_fifo->entries); +} + +int kvm_hv_vcpu_flush_tlb(struct kvm_vcpu *vcpu); + #endif diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 4ea6ddd99899..91352d692845 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -3727,7 +3727,7 @@ static void svm_flush_tlb_current(struct kvm_vcpu *vcpu) * A TLB flush for the current ASID flushes both "host" and "guest" TLB * entries, and thus is a superset of Hyper-V's fine grained flushing. */ - kvm_clear_request(KVM_REQ_HV_TLB_FLUSH, vcpu); + kvm_hv_vcpu_purge_flush_tlb(vcpu); /* * Flush only the current ASID even if the TLB flush was invoked via diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 12e49e8566d4..72ac6bf05c8b 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3425,7 +3425,7 @@ static void kvm_vcpu_flush_tlb_guest(struct kvm_vcpu *vcpu) * Flushing all "guest" TLB is always a superset of Hyper-V's fine * grained flushing. */ - kvm_clear_request(KVM_REQ_HV_TLB_FLUSH, vcpu); + kvm_hv_vcpu_purge_flush_tlb(vcpu); } @@ -10256,7 +10256,14 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) kvm_service_local_tlb_flush_requests(vcpu); - if (kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu)) + /* + * Fall back to a "full" guest flush if Hyper-V's precise + * flushing fails. Note, Hyper-V's flushing is per-vCPU, but + * the flushes are considered "remote" and not "local" because + * the requests can be initiated from other vCPUs. + */ + if (kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu) && + kvm_hv_vcpu_flush_tlb(vcpu)) kvm_vcpu_flush_tlb_guest(vcpu); if (kvm_check_request(KVM_REQ_REPORT_TPR_ACCESS, vcpu)) {