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

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.

Cc: kvm-ppc@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Gbp-Pq: Topic bugfix/x86/itlb_multihit
Gbp-Pq: Name 0001-kvm-x86-powerpc-do-not-allow-clearing-largepages-deb.patch

diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
index d7fcdfa7fee40833a2b3d8fb586d6fa13fa34b3e..ec2547cc5ecbe2096d94df0982a00f324940ff6c 100644 (file)
--- a/arch/powerpc/kvm/book3s.c
+++ b/arch/powerpc/kvm/book3s.c
@@ -36,8 +36,8 @@
 #include "book3s.h"
 #include "trace.h"
 
-#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 EXIT_DEBUG */
 
@@ -69,8 +69,8 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
        { "pthru_all",       VCPU_STAT(pthru_all) },
        { "pthru_host",      VCPU_STAT(pthru_host) },
        { "pthru_bad_aff",   VCPU_STAT(pthru_bad_aff) },
-       { "largepages_2M",    VM_STAT(num_2M_pages) },
-       { "largepages_1G",    VM_STAT(num_1G_pages) },
+       { "largepages_2M",    VM_STAT(num_2M_pages, .mode = 0444) },
+       { "largepages_1G",    VM_STAT(num_1G_pages, .mode = 0444) },
        { NULL }
 };
 

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c3db03112a4118605e0da140a748d21f83d67d22..c4667d91f92d9f24b0dc07e3237a955ac402f3ea 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -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)
@@ -212,7 +212,7 @@ 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 }

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index fcb46b3374c60967993cf6123172c35a7cac4277..719fc3e15ea4e0181f314718951f9ff4fc2505c6 100644 (file)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1090,6 +1090,7 @@ enum kvm_stat_kind {
 
 struct kvm_stat_data {
        int offset;
+       int mode;
        struct kvm *kvm;
 };
 
@@ -1097,6 +1098,7 @@ 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;

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index c6a91b044d8d62d00a259590927b83d58b853394..e15a1c41b60b3bcb22c4895fac7af47cfbec91ec 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -617,8 +617,9 @@ 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;
@@ -3930,7 +3931,9 @@ 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;
        }
@@ -4178,7 +4181,8 @@ 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]);
        }