KVM: x86: hyper-v: Allocate 'struct kvm_vcpu_hv' dynamically

Hyper-V context is only needed for guests which use Hyper-V emulation in
KVM (e.g. Windows/Hyper-V guests). 'struct kvm_vcpu_hv' is, however, quite
big, it accounts for more than 1/4 of the total 'struct kvm_vcpu_arch'
which is also quite big already. This all looks like a waste.

Allocate 'struct kvm_vcpu_hv' dynamically. This patch does not bring any
(intentional) functional change as we still allocate the context
unconditionally but it paves the way to doing that only when needed.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210126134816.1880136-13-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index b6de568..95eb6e9 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -519,6 +519,7 @@ struct kvm_vcpu_hv_synic {
 
 /* Hyper-V per vcpu emulation context */
 struct kvm_vcpu_hv {
+       struct kvm_vcpu *vcpu;
        u32 vp_index;
        u64 hv_vapic;
        s64 runtime_offset;
@@ -735,7 +736,7 @@ struct kvm_vcpu_arch {
        /* used for guest single stepping over the given code position */
        unsigned long singlestep_rip;
 
-       struct kvm_vcpu_hv hyperv;
+       struct kvm_vcpu_hv *hyperv;
        struct kvm_vcpu_xen xen;
 
        cpumask_var_t wbinvd_dirty_mask;

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 10e7ed2..333bd20 100644 (file)
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -837,6 +837,9 @@ void kvm_hv_vcpu_uninit(struct kvm_vcpu *vcpu)
 
        for (i = 0; i < ARRAY_SIZE(hv_vcpu->stimer); i++)
                stimer_cleanup(&hv_vcpu->stimer[i]);
+
+       kfree(hv_vcpu);
+       vcpu->arch.hyperv = NULL;
 }
 
 bool kvm_hv_assist_page_enabled(struct kvm_vcpu *vcpu)
@@ -886,16 +889,25 @@ static void stimer_init(struct kvm_vcpu_hv_stimer *stimer, int timer_index)
        stimer_prepare_msg(stimer);
 }
 
-void kvm_hv_vcpu_init(struct kvm_vcpu *vcpu)
+int kvm_hv_vcpu_init(struct kvm_vcpu *vcpu)
 {
-       struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
+       struct kvm_vcpu_hv *hv_vcpu;
        int i;
 
+       hv_vcpu = kzalloc(sizeof(struct kvm_vcpu_hv), GFP_KERNEL_ACCOUNT);
+       if (!hv_vcpu)
+               return -ENOMEM;
+
+       vcpu->arch.hyperv = hv_vcpu;
+       hv_vcpu->vcpu = vcpu;
+
        synic_init(&hv_vcpu->synic);
 
        bitmap_zero(hv_vcpu->stimer_pending_bitmap, HV_SYNIC_STIMER_COUNT);
        for (i = 0; i < ARRAY_SIZE(hv_vcpu->stimer); i++)
                stimer_init(&hv_vcpu->stimer[i], i);
+
+       return 0;
 }
 
 void kvm_hv_vcpu_postcreate(struct kvm_vcpu *vcpu)

diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
index 57e53a8..4bc2ab0 100644 (file)
--- a/arch/x86/kvm/hyperv.h
+++ b/arch/x86/kvm/hyperv.h
@@ -57,20 +57,19 @@ static inline struct kvm_hv *to_kvm_hv(struct kvm *kvm)
 
 static inline struct kvm_vcpu_hv *to_hv_vcpu(struct kvm_vcpu *vcpu)
 {
-       return &vcpu->arch.hyperv;
+       return vcpu->arch.hyperv;
 }
 
 static inline struct kvm_vcpu *hv_vcpu_to_vcpu(struct kvm_vcpu_hv *hv_vcpu)
 {
-       struct kvm_vcpu_arch *arch;
-
-       arch = container_of(hv_vcpu, struct kvm_vcpu_arch, hyperv);
-       return container_of(arch, struct kvm_vcpu, arch);
+       return hv_vcpu->vcpu;
 }
 
 static inline struct kvm_vcpu_hv_synic *to_hv_synic(struct kvm_vcpu *vcpu)
 {
-       return &vcpu->arch.hyperv.synic;
+       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)
@@ -101,7 +100,7 @@ int kvm_hv_synic_set_irq(struct kvm *kvm, u32 vcpu_id, u32 sint);
 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);
 
-void kvm_hv_vcpu_init(struct kvm_vcpu *vcpu);
+int kvm_hv_vcpu_init(struct kvm_vcpu *vcpu);
 void kvm_hv_vcpu_postcreate(struct kvm_vcpu *vcpu);
 void kvm_hv_vcpu_uninit(struct kvm_vcpu *vcpu);
 

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7caf95d..a75d015 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10083,11 +10083,12 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
        vcpu->arch.pending_external_vector = -1;
        vcpu->arch.preempted_in_kernel = false;
 
-       kvm_hv_vcpu_init(vcpu);
+       if (kvm_hv_vcpu_init(vcpu))
+               goto free_guest_fpu;
 
        r = static_call(kvm_x86_vcpu_create)(vcpu);
        if (r)
-               goto free_guest_fpu;
+               goto free_hv_vcpu;
 
        vcpu->arch.arch_capabilities = kvm_get_arch_capabilities();
        vcpu->arch.msr_platform_info = MSR_PLATFORM_INFO_CPUID_FAULT;
@@ -10098,6 +10099,8 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
        vcpu_put(vcpu);
        return 0;
 
+free_hv_vcpu:
+       kvm_hv_vcpu_uninit(vcpu);
 free_guest_fpu:
        kvm_free_guest_fpu(vcpu);
 free_user_fpu: