KVM: PPC: Book3S HV: Explicitly disable HPT operations on radix guests

This adds code to make sure that we don't try to access the
non-existent HPT for a radix guest using the htab file for the VM
in debugfs, a file descriptor obtained using the KVM_PPC_GET_HTAB_FD
ioctl, or via the KVM_PPC_RESIZE_HPT_{PREPARE,COMMIT} ioctls.

At present nothing bad happens if userspace does access these
interfaces on a radix guest, mostly because kvmppc_hpt_npte()
gives 0 for a radix guest, which in turn is because 1 << -4
comes out as 0 on POWER processors.  However, that relies on
undefined behaviour, so it is better to be explicit about not
accessing the HPT for a radix guest.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 7df89d58ee91cb0865e794c16f91b8e345942810..624b01175b7930ae67679a61475c69121f1b9c3d 100644 (file)
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -1454,7 +1454,7 @@ long kvm_vm_ioctl_resize_hpt_prepare(struct kvm *kvm,
        struct kvm_resize_hpt *resize;
        int ret;
 
-       if (flags != 0)
+       if (flags != 0 || kvm_is_radix(kvm))
                return -EINVAL;
 
        if (shift && ((shift < 18) || (shift > 46)))
@@ -1520,7 +1520,7 @@ long kvm_vm_ioctl_resize_hpt_commit(struct kvm *kvm,
        struct kvm_resize_hpt *resize;
        long ret;
 
-       if (flags != 0)
+       if (flags != 0 || kvm_is_radix(kvm))
                return -EINVAL;
 
        if (shift && ((shift < 18) || (shift > 46)))
@@ -1706,6 +1706,8 @@ static ssize_t kvm_htab_read(struct file *file, char __user *buf,
 
        if (!access_ok(VERIFY_WRITE, buf, count))
                return -EFAULT;
+       if (kvm_is_radix(kvm))
+               return 0;
 
        first_pass = ctx->first_pass;
        flags = ctx->flags;
@@ -1803,6 +1805,8 @@ static ssize_t kvm_htab_write(struct file *file, const char __user *buf,
 
        if (!access_ok(VERIFY_READ, buf, count))
                return -EFAULT;
+       if (kvm_is_radix(kvm))
+               return -EINVAL;
 
        /* lock out vcpus from running while we're doing this */
        mutex_lock(&kvm->lock);
@@ -2001,6 +2005,10 @@ static ssize_t debugfs_htab_read(struct file *file, char __user *buf,
        struct kvm *kvm;
        __be64 *hptp;
 
+       kvm = p->kvm;
+       if (kvm_is_radix(kvm))
+               return 0;
+
        ret = mutex_lock_interruptible(&p->mutex);
        if (ret)
                return ret;
@@ -2023,7 +2031,6 @@ static ssize_t debugfs_htab_read(struct file *file, char __user *buf,
                }
        }
 
-       kvm = p->kvm;
        i = p->hpt_index;
        hptp = (__be64 *)(kvm->arch.hpt.virt + (i * HPTE_SIZE));
        for (; len != 0 && i < kvmppc_hpt_npte(&kvm->arch.hpt);