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kvm: x86, powerpc: do not allow clearing largepages debugfs entry

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commit 833b45de69 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>
This commit is contained in:
Paolo Bonzini 2019-10-11 11:59:48 +02:00 committed by Greg Kroah-Hartman
parent 580c79e7e3
commit a991063ce5
3 changed files with 12 additions and 6 deletions
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6
arch/x86/kvm/x86.c
View file

@ -92,8 +92,8 @@ u64 __read_mostly efer_reserved_bits = ~((u64)(EFER_SCE | EFER_LME | EFER_LMA));
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 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
{ "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 }

2
include/linux/kvm_host.h
View file

@ -1034,6 +1034,7 @@ enum kvm_stat_kind {
struct kvm_stat_data {
int offset;
int mode;
struct kvm *kvm;
};
@ -1041,6 +1042,7 @@ struct kvm_stats_debugfs_item {
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;

10
virt/kvm/kvm_main.c
View file

@ -616,8 +616,9 @@ static int kvm_create_vm_debugfs(struct kvm *kvm, int fd)
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 @@ static int kvm_debugfs_open(struct inode *inode, struct file *file,
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 @@ static void kvm_init_debug(void)
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]);
}