[PATCH 07/45] KVM: x86: Allocate vcpu struct in common x86 code

Sean Christopherson
2019-10-22T01:58:47Z

Move allocation of VMX and SVM vcpus to common x86. Although the struct
being allocated is technically a VMX/SVM struct, it can be interpreted
directly as a 'struct kvm_vcpu' because of the pre-existing requirement
that 'struct kvm_vcpu' be located at offset zero of the arch/vendor vcpu
struct.

Remove the message from the build-time assertions regarding placement of
the struct, as compatibility with the arch usercopy region is no longer
the sole dependent on 'struct kvm_vcpu' being at offset zero.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/include/asm/kvm_host.h | 2 +-
arch/x86/kvm/svm.c | 28 +++++++++-------------------
arch/x86/kvm/vmx/vmx.c | 24 ++++++++----------------
arch/x86/kvm/x86.c | 16 ++++++++++++----
4 files changed, 30 insertions(+), 40 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 5d8056ff7390..77581eeb02e3 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1014,7 +1014,7 @@ struct kvm_x86_ops {
void (*vm_destroy)(struct kvm *kvm);

/* Create, but do not attach this VCPU */
- struct kvm_vcpu *(*vcpu_create)(struct kvm *kvm, unsigned id);
+ int (*vcpu_create)(struct kvm *kvm, struct kvm_vcpu *vcpu, unsigned id);
void (*vcpu_free)(struct kvm_vcpu *vcpu);
void (*vcpu_reset)(struct kvm_vcpu *vcpu, bool init_event);

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 2f66c52e1b5d..bbc5dac9d400 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -2138,9 +2138,9 @@ static int avic_init_vcpu(struct vcpu_svm *svm)
return ret;
}

-static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id)
+static int svm_create_vcpu(struct kvm *kvm, struct kvm_vcpu *vcpu,
+ unsigned int id)
{
- struct kvm_vcpu *vcpu;
struct vcpu_svm *svm;
struct page *page;
struct page *msrpm_pages;
@@ -2148,22 +2148,15 @@ static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id)
struct page *nested_msrpm_pages;
int err;

- BUILD_BUG_ON_MSG(offsetof(struct vcpu_svm, vcpu) != 0,
- "struct kvm_vcpu must be at offset 0 for arch usercopy region");
-
- svm = kmem_cache_zalloc(kvm_vcpu_cache, GFP_KERNEL_ACCOUNT);
- if (!svm) {
- err = -ENOMEM;
- goto out;
- }
- vcpu = &svm->vcpu;
+ BUILD_BUG_ON(offsetof(struct vcpu_svm, vcpu) != 0);
+ svm = to_svm(vcpu);

vcpu->arch.user_fpu = kmem_cache_zalloc(x86_fpu_cache,
GFP_KERNEL_ACCOUNT);
if (!vcpu->arch.user_fpu) {
printk(KERN_ERR "kvm: failed to allocate kvm userspace's fpu\n");
err = -ENOMEM;
- goto free_partial_svm;
+ goto out;
}

vcpu->arch.guest_fpu = kmem_cache_zalloc(x86_fpu_cache,
@@ -2176,7 +2169,7 @@ static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id)

err = kvm_vcpu_init(vcpu, kvm, id);
if (err)
- goto free_svm;
+ goto free_guest_fpu;

err = -ENOMEM;
page = alloc_page(GFP_KERNEL_ACCOUNT);
@@ -2220,7 +2213,7 @@ static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id)

svm_init_osvw(vcpu);

- return vcpu;
+ return 0;

free_page4:
__free_page(hsave_page);
@@ -2232,14 +2225,12 @@ static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id)
__free_page(page);
uninit:
kvm_vcpu_uninit(vcpu);
-free_svm:
+free_guest_fpu:
kmem_cache_free(x86_fpu_cache, vcpu->arch.guest_fpu);
free_user_fpu:
kmem_cache_free(x86_fpu_cache, vcpu->arch.user_fpu);
-free_partial_svm:
- kmem_cache_free(kvm_vcpu_cache, svm);
out:
- return ERR_PTR(err);
+ return err;
}

static void svm_clear_current_vmcb(struct vmcb *vmcb)
@@ -2268,7 +2259,6 @@ static void svm_free_vcpu(struct kvm_vcpu *vcpu)
kvm_vcpu_uninit(vcpu);
kmem_cache_free(x86_fpu_cache, vcpu->arch.user_fpu);
kmem_cache_free(x86_fpu_cache, vcpu->arch.guest_fpu);
- kmem_cache_free(kvm_vcpu_cache, svm);
}

static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 70b8d15eb2c5..832d8e38acd4 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6693,31 +6693,24 @@ static void vmx_free_vcpu(struct kvm_vcpu *vcpu)
kvm_vcpu_uninit(vcpu);
kmem_cache_free(x86_fpu_cache, vcpu->arch.user_fpu);
kmem_cache_free(x86_fpu_cache, vcpu->arch.guest_fpu);
- kmem_cache_free(kvm_vcpu_cache, vmx);
}

-static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
+static int vmx_create_vcpu(struct kvm *kvm, struct kvm_vcpu *vcpu,
+ unsigned int id)
{
- struct kvm_vcpu *vcpu;
struct vcpu_vmx *vmx;
unsigned long *msr_bitmap;
int cpu, err;

- BUILD_BUG_ON_MSG(offsetof(struct vcpu_vmx, vcpu) != 0,
- "struct kvm_vcpu must be at offset 0 for arch usercopy region");
-
- vmx = kmem_cache_zalloc(kvm_vcpu_cache, GFP_KERNEL_ACCOUNT);
- if (!vmx)
- return ERR_PTR(-ENOMEM);
-
- vcpu = &vmx->vcpu;
+ BUILD_BUG_ON(offsetof(struct vcpu_vmx, vcpu) != 0);
+ vmx = to_vmx(vcpu);

vcpu->arch.user_fpu = kmem_cache_zalloc(x86_fpu_cache,
GFP_KERNEL_ACCOUNT);
if (!vcpu->arch.user_fpu) {
printk(KERN_ERR "kvm: failed to allocate kvm userspace's fpu\n");
err = -ENOMEM;
- goto free_partial_vcpu;
+ goto out;
}

vcpu->arch.guest_fpu = kmem_cache_zalloc(x86_fpu_cache,
@@ -6815,7 +6808,7 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)

vmx->ept_pointer = INVALID_PAGE;

- return vcpu;
+ return 0;

free_vmcs:
free_loaded_vmcs(vmx->loaded_vmcs);
@@ -6830,9 +6823,8 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
kmem_cache_free(x86_fpu_cache, vcpu->arch.guest_fpu);
free_user_fpu:
kmem_cache_free(x86_fpu_cache, vcpu->arch.user_fpu);
-free_partial_vcpu:
- kmem_cache_free(kvm_vcpu_cache, vmx);
- return ERR_PTR(err);
+out:
+ return err;
}

#define L1TF_MSG_SMT "L1TF CPU bug present and SMT on, data leak possible. See CVE-2018-3646 and https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html for details.\n"
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c9a291693279..45b296a9fdbb 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9012,26 +9012,34 @@ static void fx_init(struct kvm_vcpu *vcpu)

void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu)
{
- void *wbinvd_dirty_mask = vcpu->arch.wbinvd_dirty_mask;
-
kvmclock_reset(vcpu);

kvm_x86_ops->vcpu_free(vcpu);
- free_cpumask_var(wbinvd_dirty_mask);
+
+ free_cpumask_var(vcpu->arch.wbinvd_dirty_mask);
+ kmem_cache_free(kvm_vcpu_cache, vcpu);
}

struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm,
unsigned int id)
{
struct kvm_vcpu *vcpu;
+ int r;

if (kvm_check_tsc_unstable() && atomic_read(&kvm->online_vcpus) != 0)
printk_once(KERN_WARNING
"kvm: SMP vm created on host with unstable TSC; "
"guest TSC will not be reliable\n");

- vcpu = kvm_x86_ops->vcpu_create(kvm, id);
+ vcpu = kmem_cache_zalloc(kvm_vcpu_cache, GFP_KERNEL_ACCOUNT);
+ if (!vcpu)
+ return ERR_PTR(-ENOMEM);

+ r = kvm_x86_ops->vcpu_create(kvm, vcpu, id);
+ if (r) {
+ kmem_cache_free(kvm_vcpu_cache, vcpu);
+ return ERR_PTR(r);
+ }
return vcpu;
}

--
2.22.0