[PATCH v4 14/26] KVM: Move out KVM arch PM hooks and hardware enable/disable logic

From: isaku . yamahata
Date: Thu Sep 08 2022 - 19:27:17 EST

Next message: isaku . yamahata: "[PATCH v4 15/26] KVM: kvm_arch.c: Remove _nolock post fix"
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In reply to: Isaku Yamahata: "Re: [PATCH v4 13/26] KVM: Add arch hook when VM is added/deleted"
Next in thread: isaku . yamahata: "[PATCH v4 15/26] KVM: kvm_arch.c: Remove _nolock post fix"
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From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>

To make clear that those files are default implementation that KVM/x86 (and
other KVM arch in future) will override them, split out those into a single
file. Once conversions for all kvm archs are done, the file will be
deleted. kvm_arch_pre_hardware_unsetup() is introduced to avoid cross-arch
code churn for now. Once it's settled down,
kvm_arch_pre_hardware_unsetup() can be merged into
kvm_arch_hardware_unsetup() in each arch code. x86 kvm_arch_resume() needs
to be adjusted to do CPU compatibility check and virtualization hardware
enabling.

Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
---
arch/x86/kvm/x86.c | 10 ++
include/linux/kvm_host.h | 1 +
virt/kvm/kvm_arch.c | 124 +++++++++++++++++++++++-
virt/kvm/kvm_main.c | 198 +++++----------------------------------
4 files changed, 156 insertions(+), 177 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c733f65aaf3c..23623b6a789b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11854,9 +11854,19 @@ void kvm_arch_resume(int usage_count)
u64 max_tsc = 0;
bool stable, backwards_tsc = false;

+ if (kvm_arch_check_processor_compat())
+ return; /* FIXME: disable KVM. */
+
if (!usage_count)
return;

+ preempt_disable();
+ if (kvm_arch_hardware_enable()) {
+ preempt_enable();
+ return;
+ }
+ preempt_enable();
+
local_tsc = rdtsc();
stable = !kvm_check_tsc_unstable();
list_for_each_entry(kvm, &vm_list, vm_list) {
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index f78364e01ca9..60f4ae9d6f48 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1437,6 +1437,7 @@ static inline void kvm_create_vcpu_debugfs(struct kvm_vcpu *vcpu) {}
int kvm_arch_hardware_enable(void);
void kvm_arch_hardware_disable(void);
int kvm_arch_hardware_setup(void *opaque);
+void kvm_arch_pre_hardware_unsetup(void);
void kvm_arch_hardware_unsetup(void);
int kvm_arch_check_processor_compat(void);
int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu);
diff --git a/virt/kvm/kvm_arch.c b/virt/kvm/kvm_arch.c
index 0eac996f4981..32befdbf7d6e 100644
--- a/virt/kvm/kvm_arch.c
+++ b/virt/kvm/kvm_arch.c
@@ -6,49 +6,169 @@
* Author:
* Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
* <isaku.yamahata@xxxxxxxxx>
+ *
+ * TODO: Delete this file once the conversion of all KVM arch is done.
*/

#include <linux/kvm_host.h>

+static cpumask_t cpus_hardware_enabled = CPU_MASK_NONE;
+static atomic_t hardware_enable_failed;
+
__weak int kvm_arch_post_init_vm(struct kvm *kvm)
{
return 0;
}

+static void hardware_enable_nolock(void *caller_name)
+{
+ int cpu = raw_smp_processor_id();
+ int r;
+
+ WARN_ON_ONCE(preemptible());
+
+ if (cpumask_test_cpu(cpu, &cpus_hardware_enabled))
+ return;
+
+ cpumask_set_cpu(cpu, &cpus_hardware_enabled);
+
+ r = kvm_arch_hardware_enable();
+
+ if (r) {
+ cpumask_clear_cpu(cpu, &cpus_hardware_enabled);
+ atomic_inc(&hardware_enable_failed);
+ pr_warn("kvm: enabling virtualization on CPU%d failed during %s()\n",
+ cpu, (const char *)caller_name);
+ }
+}
+
+static void hardware_disable_nolock(void *junk)
+{
+ int cpu = raw_smp_processor_id();
+
+ WARN_ON_ONCE(preemptible());
+
+ if (!cpumask_test_cpu(cpu, &cpus_hardware_enabled))
+ return;
+ cpumask_clear_cpu(cpu, &cpus_hardware_enabled);
+ kvm_arch_hardware_disable();
+}
+
+__weak void kvm_arch_pre_hardware_unsetup(void)
+{
+ on_each_cpu(hardware_disable_nolock, NULL, 1);
+}
+
/*
* Called after the VM is otherwise initialized, but just before adding it to
* the vm_list.
*/
__weak int kvm_arch_add_vm(struct kvm *kvm, int usage_count)
{
- return kvm_arch_post_init_vm(kvm);
+ int r = 0;
+
+ if (usage_count != 1)
+ return 0;
+
+ atomic_set(&hardware_enable_failed, 0);
+ on_each_cpu(hardware_enable_nolock, (void *)__func__, 1);
+
+ if (atomic_read(&hardware_enable_failed)) {
+ r = -EBUSY;
+ goto err;
+ }
+
+ r = kvm_arch_post_init_vm(kvm);
+err:
+ if (r)
+ on_each_cpu(hardware_disable_nolock, NULL, 1);
+ return r;
}

__weak int kvm_arch_del_vm(int usage_count)
{
+ if (usage_count)
+ return 0;
+
+ on_each_cpu(hardware_disable_nolock, NULL, 1);
return 0;
}

__weak int kvm_arch_online_cpu(unsigned int cpu, int usage_count)
{
- return 0;
+ int ret = 0;
+
+ ret = kvm_arch_check_processor_compat();
+ if (ret)
+ return ret;
+
+ /*
+ * Abort the CPU online process if hardware virtualization cannot
+ * be enabled. Otherwise running VMs would encounter unrecoverable
+ * errors when scheduled to this CPU.
+ */
+ if (usage_count) {
+ WARN_ON_ONCE(atomic_read(&hardware_enable_failed));
+
+ /*
+ * arch callback kvm_arch_hardware_eanble() assumes that
+ * preemption is disabled for historical reason. Disable
+ * preemption until all arch callbacks are fixed.
+ */
+ preempt_disable();
+ hardware_enable_nolock((void *)__func__);
+ preempt_enable();
+ if (atomic_read(&hardware_enable_failed)) {
+ atomic_set(&hardware_enable_failed, 0);
+ ret = -EIO;
+ }
+ }
+ return ret;
}

__weak int kvm_arch_offline_cpu(unsigned int cpu, int usage_count)
{
+ if (usage_count) {
+ /*
+ * arch callback kvm_arch_hardware_disable() assumes that
+ * preemption is disabled for historical reason. Disable
+ * preemption until all arch callbacks are fixed.
+ */
+ preempt_disable();
+ hardware_disable_nolock(NULL);
+ preempt_enable();
+ }
return 0;
}

__weak int kvm_arch_reboot(int val)
{
+ on_each_cpu(hardware_disable_nolock, NULL, 1);
return NOTIFY_OK;
}

__weak int kvm_arch_suspend(int usage_count)
{
+ if (usage_count) {
+ preempt_disable();
+ hardware_disable_nolock(NULL);
+ preempt_enable();
+ }
return 0;
}

__weak void kvm_arch_resume(int usage_count)
{
+ if (kvm_arch_check_processor_compat())
+ /*
+ * No warning here because kvm_arch_check_processor_compat()
+ * would have warned with more information.
+ */
+ return; /* FIXME: disable KVM */
+
+ if (usage_count) {
+ preempt_disable();
+ hardware_enable_nolock((void *)__func__);
+ preempt_enable();
+ }
}
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 7acc35e279ec..5373127dcdb6 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -102,9 +102,7 @@ EXPORT_SYMBOL_GPL(halt_poll_ns_shrink);
DEFINE_MUTEX(kvm_lock);
LIST_HEAD(vm_list);

-static cpumask_var_t cpus_hardware_enabled;
static int kvm_usage_count;
-static atomic_t hardware_enable_failed;

static struct kmem_cache *kvm_vcpu_cache;

@@ -142,9 +140,6 @@ static int kvm_no_compat_open(struct inode *inode, struct file *file)
#define KVM_COMPAT(c) .compat_ioctl = kvm_no_compat_ioctl, \
.open = kvm_no_compat_open
#endif
-static int hardware_enable_all(void);
-static void hardware_disable_all(void);
-static void hardware_disable_nolock(void *junk);
static void kvm_del_vm(void);

static void kvm_io_bus_destroy(struct kvm_io_bus *bus);
@@ -1196,10 +1191,6 @@ static struct kvm *kvm_create_vm(unsigned long type, const char *fdname)
if (r)
goto out_err_no_arch_destroy_vm;

- r = hardware_enable_all();
- if (r)
- goto out_err_no_disable;
-
#ifdef CONFIG_HAVE_KVM_IRQFD
INIT_HLIST_HEAD(&kvm->irq_ack_notifier_list);
#endif
@@ -1216,14 +1207,28 @@ static struct kvm *kvm_create_vm(unsigned long type, const char *fdname)
if (r)
goto out_err_no_debugfs;

+ /*
+ * During onlining a CPU, cpu_online_mask is set before kvm_online_cpu()
+ * is called. on_each_cpu() between them includes the CPU. As a result,
+ * hardware_enable_nolock() may get invoked before kvm_online_cpu().
+ * This would enable hardware virtualization on that cpu without
+ * compatibility checks, which can potentially crash system or break
+ * running VMs.
+ *
+ * Disable CPU hotplug to prevent this case from happening.
+ */
+ cpus_read_lock();
mutex_lock(&kvm_lock);
+ kvm_usage_count++;
r = kvm_arch_add_vm(kvm, kvm_usage_count);
if (r) {
+ /* the following kvm_del_vm() decrements kvm_usage_count. */
mutex_unlock(&kvm_lock);
goto out_err;
}
list_add(&kvm->vm_list, &vm_list);
mutex_unlock(&kvm_lock);
+ cpus_read_unlock();

preempt_notifier_inc();
kvm_init_pm_notifier(kvm);
@@ -1240,9 +1245,7 @@ static struct kvm *kvm_create_vm(unsigned long type, const char *fdname)
mmu_notifier_unregister(&kvm->mmu_notifier, current->mm);
#endif
out_err_no_mmu_notifier:
- hardware_disable_all();
kvm_del_vm();
-out_err_no_disable:
kvm_arch_destroy_vm(kvm);
out_err_no_arch_destroy_vm:
WARN_ON_ONCE(!refcount_dec_and_test(&kvm->users_count));
@@ -1321,7 +1324,6 @@ static void kvm_destroy_vm(struct kvm *kvm)
cleanup_srcu_struct(&kvm->srcu);
kvm_arch_free_vm(kvm);
preempt_notifier_dec();
- hardware_disable_all();
kvm_del_vm();
mmdrop(mm);
module_put(kvm_chardev_ops.owner);
@@ -4986,163 +4988,37 @@ static struct miscdevice kvm_dev = {
&kvm_chardev_ops,
};

-static void hardware_enable_nolock(void *caller_name)
-{
- int cpu = raw_smp_processor_id();
- int r;
-
- WARN_ON_ONCE(preemptible());
-
- if (cpumask_test_cpu(cpu, cpus_hardware_enabled))
- return;
-
- cpumask_set_cpu(cpu, cpus_hardware_enabled);
-
- r = kvm_arch_hardware_enable();
-
- if (r) {
- cpumask_clear_cpu(cpu, cpus_hardware_enabled);
- atomic_inc(&hardware_enable_failed);
- pr_warn("kvm: enabling virtualization on CPU%d failed during %s()\n",
- cpu, (const char *)caller_name);
- }
-}
-
static int kvm_online_cpu(unsigned int cpu)
{
int ret;

- ret = kvm_arch_check_processor_compat();
- if (ret)
- return ret;
-
mutex_lock(&kvm_lock);
- /*
- * Abort the CPU online process if hardware virtualization cannot
- * be enabled. Otherwise running VMs would encounter unrecoverable
- * errors when scheduled to this CPU.
- */
- if (kvm_usage_count) {
- WARN_ON_ONCE(atomic_read(&hardware_enable_failed));
-
- /*
- * arch callback kvm_arch_hardware_eanble() assumes that
- * preemption is disabled for historical reason. Disable
- * preemption until all arch callbacks are fixed.
- */
- preempt_disable();
- hardware_enable_nolock((void *)__func__);
- preempt_enable();
- if (atomic_read(&hardware_enable_failed)) {
- atomic_set(&hardware_enable_failed, 0);
- ret = -EIO;
- } else {
- ret = kvm_arch_online_cpu(cpu, kvm_usage_count);
- if (ret)
- hardware_disable_nolock(NULL);
- }
- }
+ ret = kvm_arch_online_cpu(cpu, kvm_usage_count);
mutex_unlock(&kvm_lock);
return ret;
}

-static void hardware_disable_nolock(void *junk)
-{
- int cpu = raw_smp_processor_id();
-
- WARN_ON_ONCE(preemptible());
-
- if (!cpumask_test_cpu(cpu, cpus_hardware_enabled))
- return;
- cpumask_clear_cpu(cpu, cpus_hardware_enabled);
- kvm_arch_hardware_disable();
-}
-
static int kvm_offline_cpu(unsigned int cpu)
{
- int ret = 0;
+ int ret;

mutex_lock(&kvm_lock);
- if (kvm_usage_count) {
- /*
- * arch callback kvm_arch_hardware_disable() assumes that
- * preemption is disabled for historical reason. Disable
- * preemption until all arch callbacks are fixed.
- */
- preempt_disable();
- hardware_disable_nolock(NULL);
- ret = kvm_arch_offline_cpu(cpu, kvm_usage_count);
- if (ret) {
- (void)hardware_enable_nolock(NULL);
- atomic_set(&hardware_enable_failed, 0);
- }
- preempt_enable();
- }
+ ret = kvm_arch_offline_cpu(cpu, kvm_usage_count);
mutex_unlock(&kvm_lock);
return ret;
}

-static void hardware_disable_all_nolock(void)
-{
- BUG_ON(!kvm_usage_count);
-
- kvm_usage_count--;
- if (!kvm_usage_count)
- on_each_cpu(hardware_disable_nolock, NULL, 1);
-}
-
-static void hardware_disable_all(void)
-{
- cpus_read_lock();
- mutex_lock(&kvm_lock);
- hardware_disable_all_nolock();
- mutex_unlock(&kvm_lock);
- cpus_read_unlock();
-}
-
static void kvm_del_vm(void)
{
cpus_read_lock();
mutex_lock(&kvm_lock);
+ WARN_ON_ONCE(!kvm_usage_count);
+ kvm_usage_count--;
kvm_arch_del_vm(kvm_usage_count);
mutex_unlock(&kvm_lock);
cpus_read_unlock();
}

-static int hardware_enable_all(void)
-{
- int r = 0;
-
- /*
- * During onlining a CPU, cpu_online_mask is set before kvm_online_cpu()
- * is called. on_each_cpu() between them includes the CPU. As a result,
- * hardware_enable_nolock() may get invoked before kvm_online_cpu().
- * This would enable hardware virtualization on that cpu without
- * compatibility checks, which can potentially crash system or break
- * running VMs.
- *
- * Disable CPU hotplug to prevent this case from happening.
- */
- cpus_read_lock();
- mutex_lock(&kvm_lock);
-
- kvm_usage_count++;
- if (kvm_usage_count == 1) {
- atomic_set(&hardware_enable_failed, 0);
- on_each_cpu(hardware_enable_nolock, (void *)__func__, 1);
-
- if (atomic_read(&hardware_enable_failed)) {
- hardware_disable_all_nolock();
- r = -EBUSY;
- }
- }
-
- mutex_unlock(&kvm_lock);
- cpus_read_unlock();
-
- return r;
-}
-
static int kvm_reboot(struct notifier_block *notifier, unsigned long val,
void *v)
{
@@ -5160,7 +5036,6 @@ static int kvm_reboot(struct notifier_block *notifier, unsigned long val,
/* This hook is called without cpuhotplug disabled. */
cpus_read_lock();
mutex_lock(&kvm_lock);
- on_each_cpu(hardware_disable_nolock, NULL, 1);
r = kvm_arch_reboot(val);
mutex_unlock(&kvm_lock);
cpus_read_unlock();
@@ -5753,40 +5628,19 @@ static void kvm_init_debug(void)

static int kvm_suspend(void)
{
- int ret;
-
/*
* The caller ensures that CPU hotlug is disabled by
* cpu_hotplug_disable() and other CPUs are offlined. No need for
* locking.
*/
lockdep_assert_not_held(&kvm_lock);
-
- preempt_disable();
- if (kvm_usage_count)
- hardware_disable_nolock(NULL);
- ret = kvm_arch_suspend(kvm_usage_count);
- preempt_enable();
-
- return ret;
+ return kvm_arch_suspend(kvm_usage_count);
}

static void kvm_resume(void)
{
lockdep_assert_not_held(&kvm_lock);
-
- if (kvm_arch_check_processor_compat())
- /*
- * No warning here because kvm_arch_check_processor_compat()
- * would have warned with more information.
- */
- return; /* FIXME: disable KVM */
-
- preempt_disable();
- if (kvm_usage_count)
- hardware_enable_nolock((void *)__func__);
kvm_arch_resume(kvm_usage_count);
- preempt_enable();
}

static struct syscore_ops kvm_syscore_ops = {
@@ -5924,11 +5778,6 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
if (r)
goto out_irqfd;

- if (!zalloc_cpumask_var(&cpus_hardware_enabled, GFP_KERNEL)) {
- r = -ENOMEM;
- goto out_free_0;
- }
-
r = kvm_arch_hardware_setup(opaque);
if (r < 0)
goto out_free_1;
@@ -6005,8 +5854,6 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
out_free_2:
kvm_arch_hardware_unsetup();
out_free_1:
- free_cpumask_var(cpus_hardware_enabled);
-out_free_0:
kvm_irqfd_exit();
out_irqfd:
kvm_arch_exit();
@@ -6028,11 +5875,12 @@ void kvm_exit(void)
unregister_syscore_ops(&kvm_syscore_ops);
unregister_reboot_notifier(&kvm_reboot_notifier);
cpuhp_remove_state_nocalls(CPUHP_AP_KVM_ONLINE);
- on_each_cpu(hardware_disable_nolock, NULL, 1);
+ cpus_read_lock();
+ kvm_arch_pre_hardware_unsetup();
kvm_arch_hardware_unsetup();
+ cpus_read_unlock();
kvm_arch_exit();
kvm_irqfd_exit();
- free_cpumask_var(cpus_hardware_enabled);
kvm_vfio_ops_exit();
}
EXPORT_SYMBOL_GPL(kvm_exit);
--
2.25.1

Next message: isaku . yamahata: "[PATCH v4 15/26] KVM: kvm_arch.c: Remove _nolock post fix"
Previous message: isaku . yamahata: "[PATCH v4 13/26] KVM: Add arch hook when VM is added/deleted"
In reply to: Isaku Yamahata: "Re: [PATCH v4 13/26] KVM: Add arch hook when VM is added/deleted"
Next in thread: isaku . yamahata: "[PATCH v4 15/26] KVM: kvm_arch.c: Remove _nolock post fix"
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