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

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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>
This commit is contained in:
Paul Mackerras 2017-09-13 16:29:22 +10:00
parent 3f2bb76433
commit 891f1ebf65
1 changed files with 10 additions and 3 deletions
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13
arch/powerpc/kvm/book3s_64_mmu_hv.c
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@ -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);