KVM: X86: Dynamically allocate user_fpu

After reverting commit 240c35a3783a (kvm: x86: Use task structs fpu field
for user), struct kvm_vcpu is 19456 bytes on my server, PAGE_ALLOC_COSTLY_ORDER(3)
is the order at which allocations are deemed costly to service. In serveless
scenario, one host can service hundreds/thoudands firecracker/kata-container
instances, howerver, new instance will fail to launch after memory is too
fragmented to allocate kvm_vcpu struct on host, this was observed in some
cloud provider product environments.

This patch dynamically allocates user_fpu, kvm_vcpu is 15168 bytes now on my
Skylake server.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.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 b2f1ffb937affc81b4b62b63f1ca35ee6e6c84a8..e74f0711eaaf34e2bef60e5225be23ebbd1f5e08 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -616,7 +616,7 @@ struct kvm_vcpu_arch {
         * "guest_fpu" state here contains the guest FPU context, with the
         * host PRKU bits.
         */
-       struct fpu user_fpu;
+       struct fpu *user_fpu;
        struct fpu *guest_fpu;
 
        u64 xcr0;

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 19f69df9675869295764ae3a04bc1c0a5df0ff00..7eafc6907861e6d0f6b9ccfac1b2b6071238cd82 100644 (file)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -2143,12 +2143,20 @@ static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id)
                goto out;
        }
 
+       svm->vcpu.arch.user_fpu = kmem_cache_zalloc(x86_fpu_cache,
+                                                    GFP_KERNEL_ACCOUNT);
+       if (!svm->vcpu.arch.user_fpu) {
+               printk(KERN_ERR "kvm: failed to allocate kvm userspace's fpu\n");
+               err = -ENOMEM;
+               goto free_partial_svm;
+       }
+
        svm->vcpu.arch.guest_fpu = kmem_cache_zalloc(x86_fpu_cache,
                                                     GFP_KERNEL_ACCOUNT);
        if (!svm->vcpu.arch.guest_fpu) {
                printk(KERN_ERR "kvm: failed to allocate vcpu's fpu\n");
                err = -ENOMEM;
-               goto free_partial_svm;
+               goto free_user_fpu;
        }
 
        err = kvm_vcpu_init(&svm->vcpu, kvm, id);
@@ -2211,6 +2219,8 @@ uninit:
        kvm_vcpu_uninit(&svm->vcpu);
 free_svm:
        kmem_cache_free(x86_fpu_cache, svm->vcpu.arch.guest_fpu);
+free_user_fpu:
+       kmem_cache_free(x86_fpu_cache, svm->vcpu.arch.user_fpu);
 free_partial_svm:
        kmem_cache_free(kvm_vcpu_cache, svm);
 out:
@@ -2241,6 +2251,7 @@ static void svm_free_vcpu(struct kvm_vcpu *vcpu)
        __free_page(virt_to_page(svm->nested.hsave));
        __free_pages(virt_to_page(svm->nested.msrpm), MSRPM_ALLOC_ORDER);
        kvm_vcpu_uninit(vcpu);
+       kmem_cache_free(x86_fpu_cache, svm->vcpu.arch.user_fpu);
        kmem_cache_free(x86_fpu_cache, svm->vcpu.arch.guest_fpu);
        kmem_cache_free(kvm_vcpu_cache, svm);
 }

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index a279447eb75b6172ac470cd95e84b3e56f92ac90..074385c86c094be7c79606392dd840118331b9ef 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6598,6 +6598,7 @@ static void vmx_free_vcpu(struct kvm_vcpu *vcpu)
        free_loaded_vmcs(vmx->loaded_vmcs);
        kfree(vmx->guest_msrs);
        kvm_vcpu_uninit(vcpu);
+       kmem_cache_free(x86_fpu_cache, vmx->vcpu.arch.user_fpu);
        kmem_cache_free(x86_fpu_cache, vmx->vcpu.arch.guest_fpu);
        kmem_cache_free(kvm_vcpu_cache, vmx);
 }
@@ -6613,12 +6614,20 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
        if (!vmx)
                return ERR_PTR(-ENOMEM);
 
+       vmx->vcpu.arch.user_fpu = kmem_cache_zalloc(x86_fpu_cache,
+                       GFP_KERNEL_ACCOUNT);
+       if (!vmx->vcpu.arch.user_fpu) {
+               printk(KERN_ERR "kvm: failed to allocate kvm userspace's fpu\n");
+               err = -ENOMEM;
+               goto free_partial_vcpu;
+       }
+
        vmx->vcpu.arch.guest_fpu = kmem_cache_zalloc(x86_fpu_cache,
                        GFP_KERNEL_ACCOUNT);
        if (!vmx->vcpu.arch.guest_fpu) {
                printk(KERN_ERR "kvm: failed to allocate vcpu's fpu\n");
                err = -ENOMEM;
-               goto free_partial_vcpu;
+               goto free_user_fpu;
        }
 
        vmx->vpid = allocate_vpid();
@@ -6721,6 +6730,8 @@ uninit_vcpu:
 free_vcpu:
        free_vpid(vmx->vpid);
        kmem_cache_free(x86_fpu_cache, vmx->vcpu.arch.guest_fpu);
+free_user_fpu:
+       kmem_cache_free(x86_fpu_cache, vmx->vcpu.arch.user_fpu);
 free_partial_vcpu:
        kmem_cache_free(kvm_vcpu_cache, vmx);
        return ERR_PTR(err);

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7eb56f8e2ea8df3d16dd1e290f73d2b39a27c4ce..01e18caac825b6cf5afa4c5607f8a1cbf3b8b077 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8273,7 +8273,7 @@ static void kvm_load_guest_fpu(struct kvm_vcpu *vcpu)
 {
        fpregs_lock();
 
-       copy_fpregs_to_fpstate(&vcpu->arch.user_fpu);
+       copy_fpregs_to_fpstate(vcpu->arch.user_fpu);
        /* PKRU is separately restored in kvm_x86_ops->run.  */
        __copy_kernel_to_fpregs(&vcpu->arch.guest_fpu->state,
                                ~XFEATURE_MASK_PKRU);
@@ -8290,7 +8290,7 @@ static void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
        fpregs_lock();
 
        copy_fpregs_to_fpstate(vcpu->arch.guest_fpu);
-       copy_kernel_to_fpregs(&vcpu->arch.user_fpu.state);
+       copy_kernel_to_fpregs(&vcpu->arch.user_fpu->state);
 
        fpregs_mark_activate();
        fpregs_unlock();