KVM: PPC: Use READ_ONCE when dereferencing pte_t pointer
pte can get updated from other CPUs as part of multiple activities
like THP split, huge page collapse, unmap. We need to make sure we
don't reload the pte value again and again for different checks.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_host.c
index cc536d4..5840d54 100644
--- a/arch/powerpc/kvm/e500_mmu_host.c
+++ b/arch/powerpc/kvm/e500_mmu_host.c
@@ -469,14 +469,18 @@
pgdir = vcpu_e500->vcpu.arch.pgdir;
ptep = lookup_linux_ptep(pgdir, hva, &tsize_pages);
- if (pte_present(*ptep))
- wimg = (*ptep >> PTE_WIMGE_SHIFT) & MAS2_WIMGE_MASK;
- else {
- if (printk_ratelimit())
- pr_err("%s: pte not present: gfn %lx, pfn %lx\n",
- __func__, (long)gfn, pfn);
- ret = -EINVAL;
- goto out;
+ if (ptep) {
+ pte_t pte = READ_ONCE(*ptep);
+
+ if (pte_present(pte))
+ wimg = (pte_val(pte) >> PTE_WIMGE_SHIFT) &
+ MAS2_WIMGE_MASK;
+ else {
+ pr_err_ratelimited("%s: pte not present: gfn %lx,pfn %lx\n",
+ __func__, (long)gfn, pfn);
+ ret = -EINVAL;
+ goto out;
+ }
}
kvmppc_e500_ref_setup(ref, gtlbe, pfn, wimg);