----- Original Message -----
> From: "Suraj Jitindar Singh" <sjitindarsingh@xxxxxxxxx>
> To: kvm@xxxxxxxxxxxxxxx
> Cc: pbonzini@xxxxxxxxxx, rkrcmar@xxxxxxxxxx, "Suraj Jitindar Singh" <sjitindarsingh@xxxxxxxxx>
> Sent: Friday, October 14, 2016 8:02:42 AM
> Subject: [PATCH] kvm/stats: Update kvm stats to clear on write to their debugfs entry
>
> Various kvm vm and vcpu stats are provided via debugfs entries.
> Currently there is no way to reset these stats back to zero for the system
> except by stopping all vms.
>
> Add the ability to clear (reset back to zero) these stats on a per stat
> basis by writing to the debugfs files. The stats are just reset to zero
> irrespective of what is actually written to the file.
Even though this is a debug interface, people will still rely on
underspecified APIs. Please make it fail with EINVAL unless 0 is
written. Apart from this, it's a good idea.
Paolo
>
> Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@xxxxxxxxx>
> ---
> virt/kvm/kvm_main.c | 66
> ++++++++++++++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 60 insertions(+), 6 deletions(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 81dfc73..141fc03 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -595,7 +595,7 @@ static int kvm_create_vm_debugfs(struct kvm *kvm, int fd)
> stat_data->kvm = kvm;
> stat_data->offset = p->offset;
> kvm->debugfs_stat_data[p - debugfs_entries] = stat_data;
> - if (!debugfs_create_file(p->name, 0444,
> + if (!debugfs_create_file(p->name, 0644,
> kvm->debugfs_dentry,
> stat_data,
> stat_fops_per_vm[p->kind]))
> @@ -3658,11 +3658,20 @@ static int vm_stat_get_per_vm(void *data, u64 *val)
> return 0;
> }
>
> +static int vm_stat_clear_per_vm(void *data, u64 val)
> +{
> + struct kvm_stat_data *stat_data = (struct kvm_stat_data *)data;
> +
> + *(ulong *)((void *)stat_data->kvm + stat_data->offset) = 0;
> +
> + return 0;
> +}
> +
> static int vm_stat_get_per_vm_open(struct inode *inode, struct file *file)
> {
> __simple_attr_check_format("%llu\n", 0ull);
> return kvm_debugfs_open(inode, file, vm_stat_get_per_vm,
> - NULL, "%llu\n");
> + vm_stat_clear_per_vm, "%llu\n");
> }
>
> static const struct file_operations vm_stat_get_per_vm_fops = {
> @@ -3688,11 +3697,23 @@ static int vcpu_stat_get_per_vm(void *data, u64 *val)
> return 0;
> }
>
> +static int vcpu_stat_clear_per_vm(void *data, u64 val)
> +{
> + int i;
> + struct kvm_stat_data *stat_data = (struct kvm_stat_data *)data;
> + struct kvm_vcpu *vcpu;
> +
> + kvm_for_each_vcpu(i, vcpu, stat_data->kvm)
> + *(u64 *)((void *)vcpu + stat_data->offset) = 0;
> +
> + return 0;
> +}
> +
> static int vcpu_stat_get_per_vm_open(struct inode *inode, struct file *file)
> {
> __simple_attr_check_format("%llu\n", 0ull);
> return kvm_debugfs_open(inode, file, vcpu_stat_get_per_vm,
> - NULL, "%llu\n");
> + vcpu_stat_clear_per_vm, "%llu\n");
> }
>
> static const struct file_operations vcpu_stat_get_per_vm_fops = {
> @@ -3727,7 +3748,23 @@ static int vm_stat_get(void *_offset, u64 *val)
> return 0;
> }
>
> -DEFINE_SIMPLE_ATTRIBUTE(vm_stat_fops, vm_stat_get, NULL, "%llu\n");
> +static int vm_stat_clear(void *_offset, u64 val)
> +{
> + unsigned offset = (long)_offset;
> + struct kvm *kvm;
> + struct kvm_stat_data stat_tmp = {.offset = offset};
> +
> + spin_lock(&kvm_lock);
> + list_for_each_entry(kvm, &vm_list, vm_list) {
> + stat_tmp.kvm = kvm;
> + vm_stat_clear_per_vm((void *)&stat_tmp, 0);
> + }
> + spin_unlock(&kvm_lock);
> +
> + return 0;
> +}
> +
> +DEFINE_SIMPLE_ATTRIBUTE(vm_stat_fops, vm_stat_get, vm_stat_clear, "%llu\n");
>
> static int vcpu_stat_get(void *_offset, u64 *val)
> {
> @@ -3747,7 +3784,24 @@ static int vcpu_stat_get(void *_offset, u64 *val)
> return 0;
> }
>
> -DEFINE_SIMPLE_ATTRIBUTE(vcpu_stat_fops, vcpu_stat_get, NULL, "%llu\n");
> +static int vcpu_stat_clear(void *_offset, u64 val)
> +{
> + unsigned offset = (long)_offset;
> + struct kvm *kvm;
> + struct kvm_stat_data stat_tmp = {.offset = offset};
> +
> + spin_lock(&kvm_lock);
> + list_for_each_entry(kvm, &vm_list, vm_list) {
> + stat_tmp.kvm = kvm;
> + vcpu_stat_clear_per_vm((void *)&stat_tmp, 0);
> + }
> + spin_unlock(&kvm_lock);
> +
> + return 0;
> +}
> +
> +DEFINE_SIMPLE_ATTRIBUTE(vcpu_stat_fops, vcpu_stat_get, vcpu_stat_clear,
> + "%llu\n");
>
> static const struct file_operations *stat_fops[] = {
> [KVM_STAT_VCPU] = &vcpu_stat_fops,
> @@ -3765,7 +3819,7 @@ static int kvm_init_debug(void)
>
> kvm_debugfs_num_entries = 0;
> for (p = debugfs_entries; p->name; ++p, kvm_debugfs_num_entries++) {
> - if (!debugfs_create_file(p->name, 0444, kvm_debugfs_dir,
> + if (!debugfs_create_file(p->name, 0644, kvm_debugfs_dir,
> (void *)(long)p->offset,
> stat_fops[p->kind]))
> goto out_dir;
> --
> 2.5.5
>
>
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