kvm: x86, powerpc: do not allow clearing largepages debugfs entry
commit 833b45de69a6016c4b0cebe6765d526a31a81580 upstream.
The largepages debugfs entry is incremented/decremented as shadow
pages are created or destroyed. Clearing it will result in an
underflow, which is harmless to KVM but ugly (and could be
misinterpreted by tools that use debugfs information), so make
this particular statistic read-only.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm-ppc@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2e8e9fd..5de2c4a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -92,8 +92,8 @@
static u64 __read_mostly efer_reserved_bits = ~((u64)EFER_SCE);
#endif
-#define VM_STAT(x) offsetof(struct kvm, stat.x), KVM_STAT_VM
-#define VCPU_STAT(x) offsetof(struct kvm_vcpu, stat.x), KVM_STAT_VCPU
+#define VM_STAT(x, ...) offsetof(struct kvm, stat.x), KVM_STAT_VM, ## __VA_ARGS__
+#define VCPU_STAT(x, ...) offsetof(struct kvm_vcpu, stat.x), KVM_STAT_VCPU, ## __VA_ARGS__
#define KVM_X2APIC_API_VALID_FLAGS (KVM_X2APIC_API_USE_32BIT_IDS | \
KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK)
@@ -205,7 +205,7 @@
{ "mmu_cache_miss", VM_STAT(mmu_cache_miss) },
{ "mmu_unsync", VM_STAT(mmu_unsync) },
{ "remote_tlb_flush", VM_STAT(remote_tlb_flush) },
- { "largepages", VM_STAT(lpages) },
+ { "largepages", VM_STAT(lpages, .mode = 0444) },
{ "max_mmu_page_hash_collisions",
VM_STAT(max_mmu_page_hash_collisions) },
{ NULL }
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index d42a36e..3d0a6194 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1034,6 +1034,7 @@
struct kvm_stat_data {
int offset;
+ int mode;
struct kvm *kvm;
};
@@ -1041,6 +1042,7 @@
const char *name;
int offset;
enum kvm_stat_kind kind;
+ int mode;
};
extern struct kvm_stats_debugfs_item debugfs_entries[];
extern struct dentry *kvm_debugfs_dir;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 4a584a5..0c578a1 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -616,8 +616,9 @@
stat_data->kvm = kvm;
stat_data->offset = p->offset;
+ stat_data->mode = p->mode ? p->mode : 0644;
kvm->debugfs_stat_data[p - debugfs_entries] = stat_data;
- debugfs_create_file(p->name, 0644, kvm->debugfs_dentry,
+ debugfs_create_file(p->name, stat_data->mode, kvm->debugfs_dentry,
stat_data, stat_fops_per_vm[p->kind]);
}
return 0;
@@ -3714,7 +3715,9 @@
if (!refcount_inc_not_zero(&stat_data->kvm->users_count))
return -ENOENT;
- if (simple_attr_open(inode, file, get, set, fmt)) {
+ if (simple_attr_open(inode, file, get,
+ stat_data->mode & S_IWUGO ? set : NULL,
+ fmt)) {
kvm_put_kvm(stat_data->kvm);
return -ENOMEM;
}
@@ -3962,7 +3965,8 @@
kvm_debugfs_num_entries = 0;
for (p = debugfs_entries; p->name; ++p, kvm_debugfs_num_entries++) {
- debugfs_create_file(p->name, 0644, kvm_debugfs_dir,
+ int mode = p->mode ? p->mode : 0644;
+ debugfs_create_file(p->name, mode, kvm_debugfs_dir,
(void *)(long)p->offset,
stat_fops[p->kind]);
}