KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 429 insertions, 0 deletions

diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
new file mode 100644
index 000000000..622a6553e
--- /dev/null
+++ b/arch/x86/kvm/hyperv.h
@@ -0,0 +1,429 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * KVM Microsoft Hyper-V emulation
+ *
+ * derived from arch/x86/kvm/x86.c
+ *
+ * Copyright (C) 2006 Qumranet, Inc.
+ * Copyright (C) 2008 Qumranet, Inc.
+ * Copyright IBM Corporation, 2008
+ * Copyright 2010 Red Hat, Inc. and/or its affiliates.
+ * Copyright (C) 2015 Andrey Smetanin <asmetanin@virtuozzo.com>
+ *
+ * Authors:
+ *   Avi Kivity   <avi@qumranet.com>
+ *   Yaniv Kamay  <yaniv@qumranet.com>
+ *   Amit Shah    <amit.shah@qumranet.com>
+ *   Ben-Ami Yassour <benami@il.ibm.com>
+ *   Andrey Smetanin <asmetanin@virtuozzo.com>
+ */
+
+#ifndef __ARCH_X86_KVM_HYPERV_H__
+#define __ARCH_X86_KVM_HYPERV_H__
+
+#include <linux/kvm_host.h>
+
+#include "regs.h"
+
+#ifdef CONFIG_KVM_HYPERV
+
+
+/* Hyper-V SynIC timer */
+struct kvm_vcpu_hv_stimer {
+	struct hrtimer timer;
+	int index;
+	union hv_stimer_config config;
+	u64 count;
+	u64 exp_time;
+	struct hv_message msg;
+	bool msg_pending;
+};
+
+/* Hyper-V synthetic interrupt controller (SynIC)*/
+struct kvm_vcpu_hv_synic {
+	u64 version;
+	u64 control;
+	u64 msg_page;
+	u64 evt_page;
+	atomic64_t sint[HV_SYNIC_SINT_COUNT];
+	atomic_t sint_to_gsi[HV_SYNIC_SINT_COUNT];
+	DECLARE_BITMAP(auto_eoi_bitmap, 256);
+	DECLARE_BITMAP(vec_bitmap, 256);
+	bool active;
+	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)
+
+enum hv_tlb_flush_fifos {
+	HV_L1_TLB_FLUSH_FIFO,
+	HV_L2_TLB_FLUSH_FIFO,
+	HV_NR_TLB_FLUSH_FIFOS,
+};
+
+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;
+	u32 vp_index;
+	u64 hv_vapic;
+	s64 runtime_offset;
+	struct kvm_vcpu_hv_synic synic;
+	struct kvm_hyperv_exit exit;
+	struct kvm_vcpu_hv_stimer stimer[HV_SYNIC_STIMER_COUNT];
+	DECLARE_BITMAP(stimer_pending_bitmap, HV_SYNIC_STIMER_COUNT);
+	bool enforce_cpuid;
+	struct {
+		u32 features_eax; /* HYPERV_CPUID_FEATURES.EAX */
+		u32 features_ebx; /* HYPERV_CPUID_FEATURES.EBX */
+		u32 features_edx; /* HYPERV_CPUID_FEATURES.EDX */
+		u32 enlightenments_eax; /* HYPERV_CPUID_ENLIGHTMENT_INFO.EAX */
+		u32 enlightenments_ebx; /* HYPERV_CPUID_ENLIGHTMENT_INFO.EBX */
+		u32 syndbg_cap_eax; /* HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES.EAX */
+		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[HV_NR_TLB_FLUSH_FIFOS];
+
+	/*
+	 * Preallocated buffers for handling hypercalls that pass sparse vCPU
+	 * sets (for high vCPU counts, they're too large to comfortably fit on
+	 * the stack).
+	 */
+	u64 sparse_banks[HV_MAX_SPARSE_VCPU_BANKS];
+	DECLARE_BITMAP(vcpu_mask, KVM_MAX_VCPUS);
+
+	struct hv_vp_assist_page vp_assist_page;
+
+	struct {
+		u64 pa_page_gpa;
+		u64 vm_id;
+		u32 vp_id;
+	} nested;
+};
+
+/* "Hv#1" signature */
+#define HYPERV_CPUID_SIGNATURE_EAX 0x31237648
+
+/*
+ * The #defines related to the synthetic debugger are required by KDNet, but
+ * they are not documented in the Hyper-V TLFS because the synthetic debugger
+ * functionality has been deprecated and is subject to removal in future
+ * versions of Windows.
+ */
+#define HYPERV_CPUID_SYNDBG_VENDOR_AND_MAX_FUNCTIONS	0x40000080
+#define HYPERV_CPUID_SYNDBG_INTERFACE			0x40000081
+#define HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES	0x40000082
+
+/*
+ * Hyper-V synthetic debugger platform capabilities
+ * These are HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES.EAX bits.
+ */
+#define HV_X64_SYNDBG_CAP_ALLOW_KERNEL_DEBUGGING	BIT(1)
+
+/* Hyper-V Synthetic debug options MSR */
+#define HV_X64_MSR_SYNDBG_CONTROL		0x400000F1
+#define HV_X64_MSR_SYNDBG_STATUS		0x400000F2
+#define HV_X64_MSR_SYNDBG_SEND_BUFFER		0x400000F3
+#define HV_X64_MSR_SYNDBG_RECV_BUFFER		0x400000F4
+#define HV_X64_MSR_SYNDBG_PENDING_BUFFER	0x400000F5
+#define HV_X64_MSR_SYNDBG_OPTIONS		0x400000FF
+
+/* Hyper-V HV_X64_MSR_SYNDBG_OPTIONS bits */
+#define HV_X64_SYNDBG_OPTION_USE_HCALLS		BIT(2)
+
+static inline struct kvm_hv *to_kvm_hv(struct kvm *kvm)
+{
+	return &kvm->arch.hyperv;
+}
+
+static inline struct kvm_vcpu_hv *to_hv_vcpu_safe(struct kvm_vcpu *vcpu)
+{
+	/*
+	 * Ensure the HyperV structure is fully initialized when accessing it
+	 * without holding vcpu->mutex (or some other guarantee that KVM can't
+	 * concurrently instantiate the structure).
+	 *
+	 * Pairs with the smp_store_release() in kvm_hv_vcpu_init().
+	 */
+	return smp_load_acquire(&vcpu->arch.hyperv);
+}
+
+static inline struct kvm_vcpu_hv *to_hv_vcpu(struct kvm_vcpu *vcpu)
+{
+	kvm_lockdep_assert_vcpu_is_locked_or_unreachable(vcpu);
+
+	return vcpu->arch.hyperv;
+}
+
+static inline struct kvm_vcpu_hv_synic *to_hv_synic(struct kvm_vcpu *vcpu)
+{
+	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
+
+	return &hv_vcpu->synic;
+}
+
+static inline struct kvm_vcpu *hv_synic_to_vcpu(struct kvm_vcpu_hv_synic *synic)
+{
+	struct kvm_vcpu_hv *hv_vcpu = container_of(synic, struct kvm_vcpu_hv, synic);
+
+	return hv_vcpu->vcpu;
+}
+
+static inline struct kvm_hv_syndbg *to_hv_syndbg(struct kvm_vcpu *vcpu)
+{
+	return &vcpu->kvm->arch.hyperv.hv_syndbg;
+}
+
+static inline u32 kvm_hv_get_vpindex(struct kvm_vcpu *vcpu)
+{
+	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu_safe(vcpu);
+
+	return hv_vcpu ? hv_vcpu->vp_index : vcpu->vcpu_idx;
+}
+
+int kvm_hv_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host);
+int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata, bool host);
+
+static inline bool kvm_hv_hypercall_enabled(struct kvm_vcpu *vcpu)
+{
+	return vcpu->arch.hyperv_enabled && to_kvm_hv(vcpu->kvm)->hv_guest_os_id;
+}
+
+int kvm_hv_hypercall(struct kvm_vcpu *vcpu);
+
+void kvm_hv_irq_routing_update(struct kvm *kvm);
+int kvm_hv_synic_set_irq(struct kvm_kernel_irq_routing_entry *e, struct kvm *kvm,
+			 int irq_source_id, int level, bool line_status);
+void kvm_hv_synic_send_eoi(struct kvm_vcpu *vcpu, int vector);
+int kvm_hv_activate_synic(struct kvm_vcpu *vcpu, bool dont_zero_synic_pages);
+
+static inline bool kvm_hv_synic_has_vector(struct kvm_vcpu *vcpu, int vector)
+{
+	return to_hv_vcpu(vcpu) && test_bit(vector, to_hv_synic(vcpu)->vec_bitmap);
+}
+
+static inline bool kvm_hv_synic_auto_eoi_set(struct kvm_vcpu *vcpu, int vector)
+{
+	return to_hv_vcpu(vcpu) &&
+	       test_bit(vector, to_hv_synic(vcpu)->auto_eoi_bitmap);
+}
+
+void kvm_hv_vcpu_uninit(struct kvm_vcpu *vcpu);
+
+bool kvm_hv_assist_page_enabled(struct kvm_vcpu *vcpu);
+int kvm_hv_get_assist_page(struct kvm_vcpu *vcpu);
+
+static inline struct kvm_vcpu_hv_stimer *to_hv_stimer(struct kvm_vcpu *vcpu,
+						      int timer_index)
+{
+	return &to_hv_vcpu(vcpu)->stimer[timer_index];
+}
+
+static inline struct kvm_vcpu *hv_stimer_to_vcpu(struct kvm_vcpu_hv_stimer *stimer)
+{
+	struct kvm_vcpu_hv *hv_vcpu;
+
+	hv_vcpu = container_of(stimer - stimer->index, struct kvm_vcpu_hv,
+			       stimer[0]);
+	return hv_vcpu->vcpu;
+}
+
+static inline bool kvm_hv_has_stimer_pending(struct kvm_vcpu *vcpu)
+{
+	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu_safe(vcpu);
+
+	if (!hv_vcpu)
+		return false;
+
+	return !bitmap_empty(hv_vcpu->stimer_pending_bitmap,
+			     HV_SYNIC_STIMER_COUNT);
+}
+
+/*
+ * With HV_ACCESS_TSC_INVARIANT feature, invariant TSC (CPUID.80000007H:EDX[8])
+ * is only observed after HV_X64_MSR_TSC_INVARIANT_CONTROL was written to.
+ */
+static inline bool kvm_hv_invtsc_suppressed(struct kvm_vcpu *vcpu)
+{
+	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
+
+	/*
+	 * If Hyper-V's invariant TSC control is not exposed to the guest,
+	 * the invariant TSC CPUID flag is not suppressed, Windows guests were
+	 * observed to be able to handle it correctly. Going forward, VMMs are
+	 * encouraged to enable Hyper-V's invariant TSC control when invariant
+	 * TSC CPUID flag is set to make KVM's behavior match genuine Hyper-V.
+	 */
+	if (!hv_vcpu ||
+	    !(hv_vcpu->cpuid_cache.features_eax & HV_ACCESS_TSC_INVARIANT))
+		return false;
+
+	/*
+	 * If Hyper-V's invariant TSC control is exposed to the guest, KVM is
+	 * responsible for suppressing the invariant TSC CPUID flag if the
+	 * Hyper-V control is not enabled.
+	 */
+	return !(to_kvm_hv(vcpu->kvm)->hv_invtsc_control & HV_EXPOSE_INVARIANT_TSC);
+}
+
+void kvm_hv_process_stimers(struct kvm_vcpu *vcpu);
+
+void kvm_hv_setup_tsc_page(struct kvm *kvm,
+			   struct pvclock_vcpu_time_info *hv_clock);
+void kvm_hv_request_tsc_page_update(struct kvm *kvm);
+
+void kvm_hv_xsaves_xsavec_maybe_warn(struct kvm_vcpu *vcpu);
+
+void kvm_hv_init_vm(struct kvm *kvm);
+void kvm_hv_destroy_vm(struct kvm *kvm);
+int kvm_hv_vcpu_init(struct kvm_vcpu *vcpu);
+void kvm_hv_set_cpuid(struct kvm_vcpu *vcpu, bool hyperv_enabled);
+int kvm_hv_set_enforce_cpuid(struct kvm_vcpu *vcpu, bool enforce);
+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 struct kvm_vcpu_hv_tlb_flush_fifo *kvm_hv_get_tlb_flush_fifo(struct kvm_vcpu *vcpu,
+									   bool is_guest_mode)
+{
+	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu_safe(vcpu);
+	int i = is_guest_mode ? HV_L2_TLB_FLUSH_FIFO :
+				HV_L1_TLB_FLUSH_FIFO;
+
+	if (!hv_vcpu)
+		return NULL;
+
+	return &hv_vcpu->tlb_flush_fifo[i];
+}
+
+static inline void kvm_hv_vcpu_purge_flush_tlb(struct kvm_vcpu *vcpu)
+{
+	struct kvm_vcpu_hv_tlb_flush_fifo *tlb_flush_fifo;
+
+	if (!kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu))
+		return;
+
+	tlb_flush_fifo = kvm_hv_get_tlb_flush_fifo(vcpu, is_guest_mode(vcpu));
+	if (!tlb_flush_fifo)
+		return;
+
+	kfifo_reset_out(&tlb_flush_fifo->entries);
+}
+
+static inline bool guest_hv_cpuid_has_l2_tlb_flush(struct kvm_vcpu *vcpu)
+{
+	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
+
+	return hv_vcpu &&
+		(hv_vcpu->cpuid_cache.nested_eax & HV_X64_NESTED_DIRECT_FLUSH);
+}
+
+static inline bool kvm_hv_is_tlb_flush_hcall(struct kvm_vcpu *vcpu)
+{
+	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
+	u16 code;
+
+	if (!hv_vcpu)
+		return false;
+
+	code = is_64_bit_hypercall(vcpu) ? kvm_rcx_read_raw(vcpu) :
+					   kvm_eax_read(vcpu);
+
+	return (code == HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE ||
+		code == HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST ||
+		code == HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX ||
+		code == HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX);
+}
+
+static inline int kvm_hv_verify_vp_assist(struct kvm_vcpu *vcpu)
+{
+	if (!to_hv_vcpu(vcpu))
+		return 0;
+
+	if (!kvm_hv_assist_page_enabled(vcpu))
+		return 0;
+
+	return kvm_hv_get_assist_page(vcpu);
+}
+
+static inline void kvm_hv_nested_transtion_tlb_flush(struct kvm_vcpu *vcpu,
+						     bool tdp_enabled)
+{
+	/*
+	 * KVM_REQ_HV_TLB_FLUSH flushes entries from either L1's VP_ID or
+	 * L2's VP_ID upon request from the guest. Make sure we check for
+	 * pending entries in the right FIFO upon L1/L2 transition as these
+	 * requests are put by other vCPUs asynchronously.
+	 */
+	if (to_hv_vcpu(vcpu) && tdp_enabled)
+		kvm_make_request(KVM_REQ_HV_TLB_FLUSH, vcpu);
+}
+
+int kvm_hv_vcpu_flush_tlb(struct kvm_vcpu *vcpu);
+#else /* CONFIG_KVM_HYPERV */
+static inline void kvm_hv_setup_tsc_page(struct kvm *kvm,
+					 struct pvclock_vcpu_time_info *hv_clock) {}
+static inline void kvm_hv_request_tsc_page_update(struct kvm *kvm) {}
+static inline void kvm_hv_xsaves_xsavec_maybe_warn(struct kvm_vcpu *vcpu) {}
+static inline void kvm_hv_init_vm(struct kvm *kvm) {}
+static inline void kvm_hv_destroy_vm(struct kvm *kvm) {}
+static inline int kvm_hv_vcpu_init(struct kvm_vcpu *vcpu)
+{
+	return 0;
+}
+static inline void kvm_hv_vcpu_uninit(struct kvm_vcpu *vcpu) {}
+static inline bool kvm_hv_hypercall_enabled(struct kvm_vcpu *vcpu)
+{
+	return false;
+}
+static inline int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
+{
+	return HV_STATUS_ACCESS_DENIED;
+}
+static inline void kvm_hv_vcpu_purge_flush_tlb(struct kvm_vcpu *vcpu) {}
+static inline bool kvm_hv_synic_has_vector(struct kvm_vcpu *vcpu, int vector)
+{
+	return false;
+}
+static inline bool kvm_hv_synic_auto_eoi_set(struct kvm_vcpu *vcpu, int vector)
+{
+	return false;
+}
+static inline void kvm_hv_synic_send_eoi(struct kvm_vcpu *vcpu, int vector) {}
+static inline bool kvm_hv_invtsc_suppressed(struct kvm_vcpu *vcpu)
+{
+	return false;
+}
+static inline void kvm_hv_set_cpuid(struct kvm_vcpu *vcpu, bool hyperv_enabled) {}
+static inline bool kvm_hv_has_stimer_pending(struct kvm_vcpu *vcpu)
+{
+	return false;
+}
+static inline int kvm_hv_verify_vp_assist(struct kvm_vcpu *vcpu)
+{
+	return 0;
+}
+static inline u32 kvm_hv_get_vpindex(struct kvm_vcpu *vcpu)
+{
+	return vcpu->vcpu_idx;
+}
+static inline void kvm_hv_nested_transtion_tlb_flush(struct kvm_vcpu *vcpu, bool tdp_enabled) {}
+#endif /* CONFIG_KVM_HYPERV */
+
+#endif /* __ARCH_X86_KVM_HYPERV_H__ */