[PATCH 5/6] kvm: allocate vcpu pointer array separately

From: Juergen Gross <jgross@suse.com>
To: linux-kernel@vger.kernel.org, x86@kernel.org,
	linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org
Cc: Juergen Gross <jgross@suse.com>, Marc Zyngier <maz@kernel.org>,
	James Morse <james.morse@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	kvmarm@lists.cs.columbia.edu
Subject: [PATCH 5/6] kvm: allocate vcpu pointer array separately
Date: Thu,  1 Jul 2021 17:41:04 +0200	[thread overview]
Message-ID: <20210701154105.23215-6-jgross@suse.com> (raw)
In-Reply-To: <20210701154105.23215-1-jgross@suse.com>

Prepare support of very large vcpu numbers per guest by moving the
vcpu pointer array out of struct kvm.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 arch/arm64/kvm/arm.c            | 28 ++++++++++++++++++++++++----
 arch/x86/include/asm/kvm_host.h |  5 +----
 arch/x86/kvm/x86.c              | 19 +++++++++++++++++++
 include/linux/kvm_host.h        | 17 +++++++++++++++--
 4 files changed, 59 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index e720148232a0..4f055408fe9f 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -280,18 +280,38 @@ long kvm_arch_dev_ioctl(struct file *filp,
 
 struct kvm *kvm_arch_alloc_vm(void)
 {
+	struct kvm *kvm;
+
 	if (!has_vhe())
-		return kzalloc(sizeof(struct kvm), GFP_KERNEL);
+		kvm = kzalloc(sizeof(struct kvm), GFP_KERNEL);
+	else
+		kvm = vzalloc(sizeof(struct kvm));
 
-	return vzalloc(sizeof(struct kvm));
+	if (!kvm)
+		return NULL;
+
+	if (!has_vhe())
+		kvm->vcpus = kcalloc(KVM_MAX_VCPUS, sizeof(void *), GFP_KERNEL);
+	else
+		kvm->vcpus = vzalloc(KVM_MAX_VCPUS * sizeof(void *));
+
+	if (!kvm->vcpus) {
+		kvm_arch_free_vm(kvm);
+		kvm = NULL;
+	}
+
+	return kvm;
 }
 
 void kvm_arch_free_vm(struct kvm *kvm)
 {
-	if (!has_vhe())
+	if (!has_vhe()) {
+		kfree(kvm->vcpus);
 		kfree(kvm);
-	else
+	} else {
+		vfree(kvm->vcpus);
 		vfree(kvm);
+	}
 }
 
 int kvm_arch_vcpu_precreate(struct kvm *kvm, unsigned int id)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 79138c91f83d..39cbc4b6bffb 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1440,10 +1440,7 @@ static inline void kvm_ops_static_call_update(void)
 }
 
 #define __KVM_HAVE_ARCH_VM_ALLOC
-static inline struct kvm *kvm_arch_alloc_vm(void)
-{
-	return __vmalloc(kvm_x86_ops.vm_size, GFP_KERNEL_ACCOUNT | __GFP_ZERO);
-}
+struct kvm *kvm_arch_alloc_vm(void);
 void kvm_arch_free_vm(struct kvm *kvm);
 
 #define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLB
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3af398ef1fc9..a9b0bb2221ea 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10741,9 +10741,28 @@ void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu)
 	static_call(kvm_x86_sched_in)(vcpu, cpu);
 }
 
+struct kvm *kvm_arch_alloc_vm(void)
+{
+	struct kvm *kvm;
+
+	kvm = __vmalloc(kvm_x86_ops.vm_size, GFP_KERNEL_ACCOUNT | __GFP_ZERO);
+	if (!kvm)
+		return NULL;
+
+	kvm->vcpus = __vmalloc(KVM_MAX_VCPUS * sizeof(void *),
+			       GFP_KERNEL_ACCOUNT | __GFP_ZERO);
+	if (!kvm->vcpus) {
+		vfree(kvm);
+		kvm = NULL;
+	}
+
+	return kvm;
+}
+
 void kvm_arch_free_vm(struct kvm *kvm)
 {
 	kfree(to_kvm_hv(kvm)->hv_pa_pg);
+	vfree(kvm->vcpus);
 	vfree(kvm);
 }
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 8583ed3ff344..e424ef1078a1 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -525,7 +525,7 @@ struct kvm {
 	struct mutex slots_lock;
 	struct mm_struct *mm; /* userspace tied to this vm */
 	struct kvm_memslots __rcu *memslots[KVM_ADDRESS_SPACE_NUM];
-	struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
+	struct kvm_vcpu **vcpus;
 
 	/*
 	 * created_vcpus is protected by kvm->lock, and is incremented
@@ -1022,11 +1022,24 @@ void kvm_arch_pre_destroy_vm(struct kvm *kvm);
  */
 static inline struct kvm *kvm_arch_alloc_vm(void)
 {
-	return kzalloc(sizeof(struct kvm), GFP_KERNEL);
+	struct kvm *kvm = kzalloc(sizeof(struct kvm), GFP_KERNEL);
+
+	if (!kvm)
+		return NULL;
+
+	kvm->vcpus = kcalloc(KVM_MAX_VCPUS, sizeof(void *), GFP_KERNEL);
+	if (!kvm->vcpus) {
+		kfree(kvm);
+		kvm = NULL;
+	}
+
+	return kvm;
 }
 
 static inline void kvm_arch_free_vm(struct kvm *kvm)
 {
+	if (kvm)
+		kfree(kvm->vcpus);
 	kfree(kvm);
 }
 #endif
-- 
2.26.2

