[PATCH: kvm 3/5] Fix hotadd of CPUs for KVM.

Zachary Amsden
2009-09-25T00:50:12Z

Both VMX and SVM require per-cpu memory allocation, which is done at module
init time, for only online cpus. When bringing a new CPU online, we must
also allocate this structure. The method chosen to implement this is to
make the CPU online notifier available via a call to the arch code. This
allows memory allocation to be done smoothly, without any need to allocate
extra structures.

Note: CPU up notifiers may call KVM callback before calling cpufreq callbacks.
This would causes the CPU frequency not to be detected (and it is not always
clear on non-constant TSC platforms what the bringup TSC rate will be, so the
guess of using tsc_khz could be wrong). So, we clear the rate to zero in such
a case and add logic to query it upon entry.

Signed-off-by: Zachary Amsden <zamsden@redhat.com>
---
arch/x86/include/asm/kvm_host.h | 2 ++
arch/x86/kvm/svm.c | 15 +++++++++++++--
arch/x86/kvm/vmx.c | 17 +++++++++++++++++
arch/x86/kvm/x86.c | 13 +++++++++----
include/linux/kvm_host.h | 6 ++++++
virt/kvm/kvm_main.c | 6 ++----
6 files changed, 49 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 299cc1b..b7dd14b 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -459,6 +459,7 @@ struct descriptor_table {
struct kvm_x86_ops {
int (*cpu_has_kvm_support)(void); /* __init */
int (*disabled_by_bios)(void); /* __init */
+ int (*cpu_hotadd)(int cpu);
int (*hardware_enable)(void *dummy);
void (*hardware_disable)(void *dummy);
void (*check_processor_compatibility)(void *rtn);
@@ -791,6 +792,7 @@ asmlinkage void kvm_handle_fault_on_reboot(void);
_ASM_PTR " 666b, 667b \n\t" \
".popsection"

+#define KVM_ARCH_WANT_HOTPLUG_NOTIFIER
#define KVM_ARCH_WANT_MMU_NOTIFIER
int kvm_unmap_hva(struct kvm *kvm, unsigned long hva);
int kvm_age_hva(struct kvm *kvm, unsigned long hva);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 9a4daca..8f99d0c 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -330,13 +330,13 @@ static int svm_hardware_enable(void *garbage)
return -EBUSY;

if (!has_svm()) {
- printk(KERN_ERR "svm_cpu_init: err EOPNOTSUPP on %d\n", me);
+ printk(KERN_ERR "svm_hardware_enable: err EOPNOTSUPP on %d\n", me);
return -EINVAL;
}
svm_data = per_cpu(svm_data, me);

if (!svm_data) {
- printk(KERN_ERR "svm_cpu_init: svm_data is NULL on %d\n",
+ printk(KERN_ERR "svm_hardware_enable: svm_data is NULL on %d\n",
me);
return -EINVAL;
}
@@ -394,6 +394,16 @@ err_1:

}

+static __cpuinit int svm_cpu_hotadd(int cpu)
+{
+ struct svm_cpu_data *svm_data = per_cpu(svm_data, cpu);
+
+ if (svm_data)
+ return 0;
+
+ return svm_cpu_init(cpu);
+}
+
static void set_msr_interception(u32 *msrpm, unsigned msr,
int read, int write)
{
@@ -2858,6 +2868,7 @@ static struct kvm_x86_ops svm_x86_ops = {
.hardware_setup = svm_hardware_setup,
.hardware_unsetup = svm_hardware_unsetup,
.check_processor_compatibility = svm_check_processor_compat,
+ .cpu_hotadd = svm_cpu_hotadd,
.hardware_enable = svm_hardware_enable,
.hardware_disable = svm_hardware_disable,
.cpu_has_accelerated_tpr = svm_cpu_has_accelerated_tpr,
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 3fe0d42..b8a8428 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1408,6 +1408,22 @@ static __exit void hardware_unsetup(void)
free_kvm_area();
}

+static __cpuinit int vmx_cpu_hotadd(int cpu)
+{
+ struct vmcs *vmcs;
+
+ if (per_cpu(vmxarea, cpu))
+ return 0;
+
+ vmcs = alloc_vmcs_cpu(cpu);
+ if (!vmcs)
+ return -ENOMEM;
+
+ per_cpu(vmxarea, cpu) = vmcs;
+
+ return 0;
+}
+
static void fix_pmode_dataseg(int seg, struct kvm_save_segment *save)
{
struct kvm_vmx_segment_field *sf = &kvm_vmx_segment_fields[seg];
@@ -3925,6 +3941,7 @@ static struct kvm_x86_ops vmx_x86_ops = {
.hardware_setup = hardware_setup,
.hardware_unsetup = hardware_unsetup,
.check_processor_compatibility = vmx_check_processor_compat,
+ .cpu_hotadd = vmx_cpu_hotadd,
.hardware_enable = hardware_enable,
.hardware_disable = hardware_disable,
.cpu_has_accelerated_tpr = report_flexpriority,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c18e2fc..66c6bb9 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1326,6 +1326,8 @@ out:
void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
{
kvm_x86_ops->vcpu_load(vcpu, cpu);
+ if (unlikely(per_cpu(cpu_tsc_khz, cpu) == 0))
+ per_cpu(cpu_tsc_khz, cpu) = cpufreq_quick_get(cpu);
kvm_request_guest_time_update(vcpu);
}

@@ -4699,12 +4701,15 @@ int kvm_arch_vcpu_reset(struct kvm_vcpu *vcpu)
return kvm_x86_ops->vcpu_reset(vcpu);
}

+int kvm_arch_cpu_hotadd(int cpu)
+{
+ if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
+ per_cpu(cpu_tsc_khz, cpu) = 0;
+ return kvm_x86_ops->cpu_hotadd(cpu);
+}
+
int kvm_arch_hardware_enable(void *garbage)
{
- if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) {
- int cpu = raw_smp_processor_id();
- per_cpu(cpu_tsc_khz, cpu) = cpufreq_quick_get(cpu);
- }
return kvm_x86_ops->hardware_enable(garbage);
}

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 0bf9ee9..2f075c4 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -345,6 +345,12 @@ struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, unsigned int id);
int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu);
void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu);

+#ifdef KVM_ARCH_WANT_HOTPLUG_NOTIFIER
+int kvm_arch_cpu_hotadd(int cpu);
+#else
+#define kvm_arch_cpu_hotadd(x) (0)
+#endif
+
int kvm_arch_vcpu_reset(struct kvm_vcpu *vcpu);
int kvm_arch_hardware_enable(void *garbage);
void kvm_arch_hardware_disable(void *garbage);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e27b7a9..7818b51 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1716,9 +1716,6 @@ static int kvm_cpu_hotplug(struct notifier_block *notifier, unsigned long val,
{
int cpu = (long)v;

- if (!kvm_usage_count)
- return NOTIFY_OK;
-
val &= ~CPU_TASKS_FROZEN;
switch (val) {
case CPU_DYING:
@@ -1734,7 +1731,8 @@ static int kvm_cpu_hotplug(struct notifier_block *notifier, unsigned long val,
case CPU_ONLINE:
printk(KERN_INFO "kvm: enabling virtualization on CPU%d\n",
cpu);
- smp_call_function_single(cpu, hardware_enable, NULL, 1);
+ if (!kvm_arch_cpu_hotadd(cpu))
+ smp_call_function_single(cpu, hardware_enable, NULL, 1);
break;
}
return NOTIFY_OK;
--
1.6.4.4