This patch moves the actual VMX enablement from the initialization
of the module to the creation of a VCPU.
With this approach, KVM can be easily autoloaded and does not block
other VMMs while being modprobe'd.
This improves the user experience a lot, since now other VMMs can
run, even though KVM is loaded, so users do not have to manually
load/unload KVM or any other VMM module.
Compared to the previously suggested approach "2", which would
introduce a complete framework that brings almost no benefit,
this approach enables coexistence of multiple VMMs without much
intervention. Thanks to Gerd for pointing that out.
I verified that this approach works with VirtualBox.
Signed-off-by: Alexander Graf <[EMAIL PROTECTED]>
---
arch/x86/kvm/vmx.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++----
1 files changed, 75 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 64e2439..2c48590 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -116,6 +116,9 @@ static struct page *vmx_msr_bitmap;
static DECLARE_BITMAP(vmx_vpid_bitmap, VMX_NR_VPIDS);
static DEFINE_SPINLOCK(vmx_vpid_lock);
+static int vmx_usage_count = 0;
+static DEFINE_SPINLOCK(vmx_usage_lock);
+
static struct vmcs_config {
int size;
int order;
@@ -1059,10 +1062,68 @@ static __init int vmx_disabled_by_bios(void)
/* locked but not enabled */
}
-static void hardware_enable(void *garbage)
+static void __vmx_off(void *garbage)
+{
+ asm volatile (__ex(ASM_VMX_VMXOFF) : : : "cc");
+ write_cr4(read_cr4() & ~X86_CR4_VMXE);
+}
+
+static void vmx_off(void)
+{
+ if (!vmx_usage_count)
+ return;
+
+ spin_lock(&vmx_usage_lock);
+
+ vmx_usage_count--;
+ if (vmx_usage_count == 0)
+ on_each_cpu(__vmx_off, NULL, 1);
+
+ spin_unlock(&vmx_usage_lock);
+}
+
+static void __vmx_on(void *garbage)
{
int cpu = raw_smp_processor_id();
u64 phys_addr = __pa(per_cpu(vmxarea, cpu));
+
+ write_cr4(read_cr4() | X86_CR4_VMXE); /* FIXME: not cpu hotplug safe */
+ asm volatile (ASM_VMX_VMXON_RAX
+ : : "a"(&phys_addr), "m"(phys_addr)
+ : "memory", "cc");
+}
+
+static void __vmx_check(void *r)
+{
+ if (read_cr4() & X86_CR4_VMXE)
+ *((int*)r) = -EBUSY;
+}
+
+static int vmx_on(void)
+{
+ int r = 0;
+ spin_lock(&vmx_usage_lock);
+ vmx_usage_count++;
+ if (vmx_usage_count == 1) {
+ on_each_cpu(__vmx_check, &r, 1);
+ if (r)
+ goto out_1;
+
+ on_each_cpu(__vmx_on, NULL, 1);
+ }
+
+ goto out;
+
+out_1:
+ vmx_usage_count--;
+out:
+ spin_unlock(&vmx_usage_lock);
+ return r;
+}
+
+static void hardware_enable(void *garbage)
+{
+ int cpu = raw_smp_processor_id();
u64 old;
INIT_LIST_HEAD(&per_cpu(vcpus_on_cpu, cpu));
@@ -1075,10 +1136,9 @@ static void hardware_enable(void *garbage)
wrmsrl(MSR_IA32_FEATURE_CONTROL, old |
FEATURE_CONTROL_LOCKED |
FEATURE_CONTROL_VMXON_ENABLED);
- write_cr4(read_cr4() | X86_CR4_VMXE); /* FIXME: not cpu hotplug safe */
- asm volatile (ASM_VMX_VMXON_RAX
- : : "a"(&phys_addr), "m"(phys_addr)
- : "memory", "cc");
+
+ if (vmx_usage_count)
+ __vmx_on(garbage);
}
static void vmclear_local_vcpus(void)
@@ -1094,8 +1154,9 @@ static void vmclear_local_vcpus(void)
static void hardware_disable(void *garbage)
{
vmclear_local_vcpus();
- asm volatile (__ex(ASM_VMX_VMXOFF) : : : "cc");
- write_cr4(read_cr4() & ~X86_CR4_VMXE);
+
+ if (vmx_usage_count)
+ __vmx_off(garbage);
}
static __init int adjust_vmx_controls(u32 ctl_min, u32 ctl_opt,
@@ -3490,6 +3551,7 @@ static void vmx_free_vcpu(struct kvm_vcpu *vcpu)
kfree(vmx->guest_msrs);
kvm_vcpu_uninit(vcpu);
kmem_cache_free(kvm_vcpu_cache, vmx);
+ vmx_off();
}
static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
@@ -3501,6 +3563,10 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm,
unsigned int id)
if (!vmx)
return ERR_PTR(-ENOMEM);
+ err = vmx_on();
+ if (err)
+ goto free_vmx;
+
allocate_vpid(vmx);
err = kvm_vcpu_init(&vmx->vcpu, kvm, id);
@@ -3550,6 +3616,8 @@ uninit_vcpu:
kvm_vcpu_uninit(&vmx->vcpu);
free_vcpu:
kmem_cache_free(kvm_vcpu_cache, vmx);
+free_vmx:
+ vmx_off();
return ERR_PTR(err);
}
--
1.6.0.2
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