From 7dff3364ddbc7705b8e6523f3aba1ff748b6a98f Mon Sep 17 00:00:00 2001 From: "Aneesh Kumar K.V" Date: Mon, 30 Mar 2015 10:39:12 +0530 Subject: [PATCH] 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 Signed-off-by: Michael Ellerman --- arch/powerpc/include/asm/kvm_book3s_64.h | 5 ++++- arch/powerpc/kvm/e500_mmu_host.c | 20 ++++++++++++-------- 2 files changed, 16 insertions(+), 9 deletions(-) diff --git a/arch/powerpc/include/asm/kvm_book3s_64.h b/arch/powerpc/include/asm/kvm_book3s_64.h index 14619a59ec09b..23b724c746e9d 100644 --- a/arch/powerpc/include/asm/kvm_book3s_64.h +++ b/arch/powerpc/include/asm/kvm_book3s_64.h @@ -290,7 +290,10 @@ static inline pte_t kvmppc_read_update_linux_pte(pte_t *ptep, int writing, pte_t old_pte, new_pte = __pte(0); while (1) { - old_pte = *ptep; + /* + * Make sure we don't reload from ptep + */ + old_pte = READ_ONCE(*ptep); /* * wait until _PAGE_BUSY is clear then set it atomically */ diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_host.c index cc536d4a75eff..5840d546aa031 100644 --- a/arch/powerpc/kvm/e500_mmu_host.c +++ b/arch/powerpc/kvm/e500_mmu_host.c @@ -469,14 +469,18 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500, 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); -- 2.39.5