[PATCH v6 06/19] KVM: x86/xen: Add kvm_xen_enabled static key
From: David Woodhouse <dwmw2@infradead.org>
Date: 2021-02-03 15:02:49
Subsystem:
kernel virtual machine for x86 (kvm/x86), kvm x86 xen (kvm/xen), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Sean Christopherson, Paolo Bonzini, David Woodhouse, Paul Durrant, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
From: David Woodhouse <redacted> The code paths for Xen support are all fairly lightweight but if we hide them behind this, they're even *more* lightweight for any system which isn't actually hosting Xen guests. Signed-off-by: David Woodhouse <redacted> --- arch/x86/kvm/x86.c | 2 ++ arch/x86/kvm/xen.c | 17 +++++++++++++++++ arch/x86/kvm/xen.h | 10 ++++++++-- 3 files changed, 27 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a74ae5f70bdc..d98e08faea23 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c@@ -7953,6 +7953,7 @@ void kvm_arch_exit(void) kvm_mmu_module_exit(); free_percpu(user_return_msrs); kmem_cache_destroy(x86_fpu_cache); + WARN_ON(static_branch_unlikely(&kvm_xen_enabled.key)); } static int __kvm_vcpu_halt(struct kvm_vcpu *vcpu, int state, int reason)
@@ -10529,6 +10530,7 @@ void kvm_arch_destroy_vm(struct kvm *kvm) kfree(srcu_dereference_check(kvm->arch.pmu_event_filter, &kvm->srcu, 1)); kvm_mmu_uninit_vm(kvm); kvm_page_track_cleanup(kvm); + kvm_xen_destroy_vm(kvm); kvm_hv_destroy_vm(kvm); }
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index b52549fc6dbc..7d03d918e595 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c@@ -16,6 +16,8 @@ #include "trace.h" +DEFINE_STATIC_KEY_DEFERRED_FALSE(kvm_xen_enabled, HZ); + int kvm_xen_write_hypercall_page(struct kvm_vcpu *vcpu, u64 data) { struct kvm *kvm = vcpu->kvm;
@@ -93,10 +95,25 @@ int kvm_xen_hvm_config(struct kvm *kvm, struct kvm_xen_hvm_config *xhc) xhc->blob_size_32 || xhc->blob_size_64)) return -EINVAL; + mutex_lock(&kvm->lock); + + if (xhc->msr && !kvm->arch.xen_hvm_config.msr) + static_branch_inc(&kvm_xen_enabled.key); + else if (!xhc->msr && kvm->arch.xen_hvm_config.msr) + static_branch_slow_dec_deferred(&kvm_xen_enabled); + memcpy(&kvm->arch.xen_hvm_config, xhc, sizeof(*xhc)); + + mutex_unlock(&kvm->lock); return 0; } +void kvm_xen_destroy_vm(struct kvm *kvm) +{ + if (kvm->arch.xen_hvm_config.msr) + static_branch_slow_dec_deferred(&kvm_xen_enabled); +} + static int kvm_xen_hypercall_set_result(struct kvm_vcpu *vcpu, u64 result) { kvm_rax_write(vcpu, result);
diff --git a/arch/x86/kvm/xen.h b/arch/x86/kvm/xen.h
index 28e9c9892628..ec3d8f6d0ef5 100644
--- a/arch/x86/kvm/xen.h
+++ b/arch/x86/kvm/xen.h@@ -9,14 +9,20 @@ #ifndef __ARCH_X86_KVM_XEN_H__ #define __ARCH_X86_KVM_XEN_H__ +#include <linux/jump_label_ratelimit.h> + +extern struct static_key_false_deferred kvm_xen_enabled; + int kvm_xen_hypercall(struct kvm_vcpu *vcpu); int kvm_xen_write_hypercall_page(struct kvm_vcpu *vcpu, u64 data); int kvm_xen_hvm_config(struct kvm *kvm, struct kvm_xen_hvm_config *xhc); +void kvm_xen_destroy_vm(struct kvm *kvm); static inline bool kvm_xen_hypercall_enabled(struct kvm *kvm) { - return kvm->arch.xen_hvm_config.flags & - KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL; + return static_branch_unlikely(&kvm_xen_enabled.key) && + (kvm->arch.xen_hvm_config.flags & + KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL); } #endif /* __ARCH_X86_KVM_XEN_H__ */
--
2.29.2