From patchwork Thu Mar 28 13:36:06 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Marc Zyngier X-Patchwork-Id: 10874981 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D38BC922 for ; Thu, 28 Mar 2019 13:37:36 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B89DC28DBC for ; Thu, 28 Mar 2019 13:37:36 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id AC2FB28DC2; Thu, 28 Mar 2019 13:37:36 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED autolearn=unavailable version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 1AB2828DBC for ; Thu, 28 Mar 2019 13:37:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Kk8I/zOKW83scwOlmVwjAHk5ra6EVwrQ6Rueyy+HRpI=; b=sqCBjlSGjY/JBF gxY5xreIFJf9LjBLgVperJazAzyPDms3Wb3IzDvncD5o0/vDpXcU2npYQbreurIYxERdCrnpgk/Fy Q8f0yXRNNsMeZKFFHqTmuc/u/QduqEiC2n2w07l5srC3bgLVecUO1wEGe5fBr2z57FHnZvx6hC7/C FocDkl9jOrP9H9aoNCZRHcEXOj8UAu3M07MmAv3pjQGOkZSjgZ/gDqkFkJVNS5FTmhZh/VfGklTDW qecaMwqb89xEWvxXCXl/xws5PIPOhu8FDa801BWJPqdnQNW3wdC3GBTOJpF+8gxrt+FMvD1XBLKNR 6HqRczJJUPeTgLtbPjMw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h9VDl-00022K-Pl; Thu, 28 Mar 2019 13:37:29 +0000 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70] helo=foss.arm.com) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h9VDB-0001QY-FU for linux-arm-kernel@lists.infradead.org; Thu, 28 Mar 2019 13:37:01 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 37A1A15AB; Thu, 28 Mar 2019 06:36:52 -0700 (PDT) Received: from filthy-habits.cambridge.arm.com (filthy-habits.cambridge.arm.com [10.1.196.92]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8A9073F59C; Thu, 28 Mar 2019 06:36:49 -0700 (PDT) From: Marc Zyngier To: Paolo Bonzini , =?utf-8?b?UmFkaW0gS3LEjW3DocWZ?= Subject: [PATCH 6/8] KVM: arm/arm64: Fix handling of stage2 huge mappings Date: Thu, 28 Mar 2019 13:36:06 +0000 Message-Id: <20190328133608.110805-7-marc.zyngier@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190328133608.110805-1-marc.zyngier@arm.com> References: <20190328133608.110805-1-marc.zyngier@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190328_063653_938096_12E21C25 X-CRM114-Status: GOOD ( 19.06 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kvm@vger.kernel.org, Suzuki K Poulose , Julien Thierry , YueHaibing , Zheng Xiang , Shameerali Kolothum Thodi , Christoffer Dall , Eric Auger , Julien Grall , James Morse , Nianyao Tang , Zenghui Yu , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP From: Suzuki K Poulose We rely on the mmu_notifier call backs to handle the split/merge of huge pages and thus we are guaranteed that, while creating a block mapping, either the entire block is unmapped at stage2 or it is missing permission. However, we miss a case where the block mapping is split for dirty logging case and then could later be made block mapping, if we cancel the dirty logging. This not only creates inconsistent TLB entries for the pages in the the block, but also leakes the table pages for PMD level. Handle this corner case for the huge mappings at stage2 by unmapping the non-huge mapping for the block. This could potentially release the upper level table. So we need to restart the table walk once we unmap the range. Fixes : ad361f093c1e31d ("KVM: ARM: Support hugetlbfs backed huge pages") Reported-by: Zheng Xiang Cc: Zheng Xiang Cc: Zenghui Yu Cc: Christoffer Dall Signed-off-by: Suzuki K Poulose Signed-off-by: Marc Zyngier --- arch/arm/include/asm/stage2_pgtable.h | 2 + virt/kvm/arm/mmu.c | 59 +++++++++++++++++++-------- 2 files changed, 45 insertions(+), 16 deletions(-) diff --git a/arch/arm/include/asm/stage2_pgtable.h b/arch/arm/include/asm/stage2_pgtable.h index de2089501b8b..9e11dce55e06 100644 --- a/arch/arm/include/asm/stage2_pgtable.h +++ b/arch/arm/include/asm/stage2_pgtable.h @@ -75,6 +75,8 @@ static inline bool kvm_stage2_has_pud(struct kvm *kvm) #define S2_PMD_MASK PMD_MASK #define S2_PMD_SIZE PMD_SIZE +#define S2_PUD_MASK PUD_MASK +#define S2_PUD_SIZE PUD_SIZE static inline bool kvm_stage2_has_pmd(struct kvm *kvm) { diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c index bcdf978c0d1d..f9da2fad9bd6 100644 --- a/virt/kvm/arm/mmu.c +++ b/virt/kvm/arm/mmu.c @@ -1067,25 +1067,43 @@ static int stage2_set_pmd_huge(struct kvm *kvm, struct kvm_mmu_memory_cache { pmd_t *pmd, old_pmd; +retry: pmd = stage2_get_pmd(kvm, cache, addr); VM_BUG_ON(!pmd); old_pmd = *pmd; + /* + * Multiple vcpus faulting on the same PMD entry, can + * lead to them sequentially updating the PMD with the + * same value. Following the break-before-make + * (pmd_clear() followed by tlb_flush()) process can + * hinder forward progress due to refaults generated + * on missing translations. + * + * Skip updating the page table if the entry is + * unchanged. + */ + if (pmd_val(old_pmd) == pmd_val(*new_pmd)) + return 0; + if (pmd_present(old_pmd)) { /* - * Multiple vcpus faulting on the same PMD entry, can - * lead to them sequentially updating the PMD with the - * same value. Following the break-before-make - * (pmd_clear() followed by tlb_flush()) process can - * hinder forward progress due to refaults generated - * on missing translations. + * If we already have PTE level mapping for this block, + * we must unmap it to avoid inconsistent TLB state and + * leaking the table page. We could end up in this situation + * if the memory slot was marked for dirty logging and was + * reverted, leaving PTE level mappings for the pages accessed + * during the period. So, unmap the PTE level mapping for this + * block and retry, as we could have released the upper level + * table in the process. * - * Skip updating the page table if the entry is - * unchanged. + * Normal THP split/merge follows mmu_notifier callbacks and do + * get handled accordingly. */ - if (pmd_val(old_pmd) == pmd_val(*new_pmd)) - return 0; - + if (!pmd_thp_or_huge(old_pmd)) { + unmap_stage2_range(kvm, addr & S2_PMD_MASK, S2_PMD_SIZE); + goto retry; + } /* * Mapping in huge pages should only happen through a * fault. If a page is merged into a transparent huge @@ -1097,8 +1115,7 @@ static int stage2_set_pmd_huge(struct kvm *kvm, struct kvm_mmu_memory_cache * should become splitting first, unmapped, merged, * and mapped back in on-demand. */ - VM_BUG_ON(pmd_pfn(old_pmd) != pmd_pfn(*new_pmd)); - + WARN_ON_ONCE(pmd_pfn(old_pmd) != pmd_pfn(*new_pmd)); pmd_clear(pmd); kvm_tlb_flush_vmid_ipa(kvm, addr); } else { @@ -1114,6 +1131,7 @@ static int stage2_set_pud_huge(struct kvm *kvm, struct kvm_mmu_memory_cache *cac { pud_t *pudp, old_pud; +retry: pudp = stage2_get_pud(kvm, cache, addr); VM_BUG_ON(!pudp); @@ -1121,14 +1139,23 @@ static int stage2_set_pud_huge(struct kvm *kvm, struct kvm_mmu_memory_cache *cac /* * A large number of vcpus faulting on the same stage 2 entry, - * can lead to a refault due to the - * stage2_pud_clear()/tlb_flush(). Skip updating the page - * tables if there is no change. + * can lead to a refault due to the stage2_pud_clear()/tlb_flush(). + * Skip updating the page tables if there is no change. */ if (pud_val(old_pud) == pud_val(*new_pudp)) return 0; if (stage2_pud_present(kvm, old_pud)) { + /* + * If we already have table level mapping for this block, unmap + * the range for this block and retry. + */ + if (!stage2_pud_huge(kvm, old_pud)) { + unmap_stage2_range(kvm, addr & S2_PUD_MASK, S2_PUD_SIZE); + goto retry; + } + + WARN_ON_ONCE(kvm_pud_pfn(old_pud) != kvm_pud_pfn(*new_pudp)); stage2_pud_clear(kvm, pudp); kvm_tlb_flush_vmid_ipa(kvm, addr); } else {