From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e23smtp02.au.ibm.com (e23smtp02.au.ibm.com [202.81.31.144]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 8029D1A1A1B for ; Wed, 25 Mar 2015 22:09:17 +1100 (AEDT) Received: from /spool/local by e23smtp02.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 25 Mar 2015 21:09:13 +1000 Received: from d23relay10.au.ibm.com (d23relay10.au.ibm.com [9.190.26.77]) by d23dlp03.au.ibm.com (Postfix) with ESMTP id D07B63578048 for ; Wed, 25 Mar 2015 22:09:10 +1100 (EST) Received: from d23av03.au.ibm.com (d23av03.au.ibm.com [9.190.234.97]) by d23relay10.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id t2PB92GD47251532 for ; Wed, 25 Mar 2015 22:09:10 +1100 Received: from d23av03.au.ibm.com (localhost [127.0.0.1]) by d23av03.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id t2PB8b8X013155 for ; Wed, 25 Mar 2015 22:08:37 +1100 From: "Aneesh Kumar K.V" To: benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au Subject: [PATCH 1/2] KVM: PPC: Use ACCESS_ONCE when dereferencing pte_t pointer Date: Wed, 25 Mar 2015 16:38:05 +0530 Message-Id: <1427281687-11089-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Cc: linuxppc-dev@lists.ozlabs.org, "Aneesh Kumar K.V" List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 --- NOTE: The patch is on top of "[PATCH 4/6] powerpc: Fix compile errors with STRICT_MM_TYPECHECKS enabled" 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 cc073a7ac2b7..f06820c67175 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 cc536d4a75ef..5840d546aa03 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); -- 2.1.0