From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A8159C43387 for ; Wed, 9 Jan 2019 09:42:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7890A214C6 for ; Wed, 9 Jan 2019 09:42:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=amazon.de header.i=@amazon.de header.b="pubBVEM9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730429AbfAIJmZ (ORCPT ); Wed, 9 Jan 2019 04:42:25 -0500 Received: from smtp-fw-33001.amazon.com ([207.171.190.10]:7747 "EHLO smtp-fw-33001.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730382AbfAIJmX (ORCPT ); Wed, 9 Jan 2019 04:42:23 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.de; i=@amazon.de; q=dns/txt; s=amazon201209; t=1547026943; x=1578562943; h=from:to:cc:subject:date:message-id:in-reply-to: references; bh=IsQIxzG6cbItOicp55m744yHgpadEsDovfCXfzq+GpQ=; b=pubBVEM9PryNa/OfHHuGh+4Odx1VuqAIrmvMUVf9xxUG6/zhjIMNBgFa K60exyx4AfqYbc1xQ1DxATBSkSfd29RLcyagx0FTPCAXtnXo7HUaol5VU g20CSo81fXJpxiPryLkYc2Lo1OfLODgxc8UhbdKW4HtKM0Cq7Kw17tgv+ 4=; X-IronPort-AV: E=Sophos;i="5.56,253,1539648000"; d="scan'208";a="775449722" Received: from sea3-co-svc-lb6-vlan2.sea.amazon.com (HELO email-inbound-relay-2c-397e131e.us-west-2.amazon.com) ([10.47.22.34]) by smtp-border-fw-out-33001.sea14.amazon.com with ESMTP; 09 Jan 2019 09:42:19 +0000 Received: from u54e1ad5160425a4b64ea.ant.amazon.com (pdx2-ws-svc-lb17-vlan2.amazon.com [10.247.140.66]) by email-inbound-relay-2c-397e131e.us-west-2.amazon.com (Postfix) with ESMTPS id 5B13CA297B; Wed, 9 Jan 2019 09:42:19 +0000 (UTC) Received: from u54e1ad5160425a4b64ea.ant.amazon.com (localhost [127.0.0.1]) by u54e1ad5160425a4b64ea.ant.amazon.com (8.15.2/8.15.2/Debian-3) with ESMTP id x099gHGx031303; Wed, 9 Jan 2019 10:42:17 +0100 Received: (from karahmed@localhost) by u54e1ad5160425a4b64ea.ant.amazon.com (8.15.2/8.15.2/Submit) id x099gHJM031302; Wed, 9 Jan 2019 10:42:17 +0100 From: KarimAllah Ahmed To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, pbonzini@redhat.com, rkrcmar@redhat.com Cc: Filippo Sironi , KarimAllah Ahmed Subject: [PATCH v5 03/13] X86/KVM: Handle PFNs outside of kernel reach when touching GPTEs Date: Wed, 9 Jan 2019 10:42:03 +0100 Message-Id: <1547026933-31226-4-git-send-email-karahmed@amazon.de> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1547026933-31226-1-git-send-email-karahmed@amazon.de> References: <1547026933-31226-1-git-send-email-karahmed@amazon.de> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Filippo Sironi cmpxchg_gpte() calls get_user_pages_fast() to retrieve the number of pages and the respective struct page to map in the kernel virtual address space. This doesn't work if get_user_pages_fast() is invoked with a userspace virtual address that's backed by PFNs outside of kernel reach (e.g., when limiting the kernel memory with mem= in the command line and using /dev/mem to map memory). If get_user_pages_fast() fails, look up the VMA that back the userspace virtual address, compute the PFN and the physical address, and map it in the kernel virtual address space with memremap(). Signed-off-by: Filippo Sironi Signed-off-by: KarimAllah Ahmed --- arch/x86/kvm/paging_tmpl.h | 38 +++++++++++++++++++++++++++++--------- 1 file changed, 29 insertions(+), 9 deletions(-) diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index 6bdca39..c40af67 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -141,15 +141,35 @@ static int FNAME(cmpxchg_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, struct page *page; npages = get_user_pages_fast((unsigned long)ptep_user, 1, 1, &page); - /* Check if the user is doing something meaningless. */ - if (unlikely(npages != 1)) - return -EFAULT; - - table = kmap_atomic(page); - ret = CMPXCHG(&table[index], orig_pte, new_pte); - kunmap_atomic(table); - - kvm_release_page_dirty(page); + if (likely(npages == 1)) { + table = kmap_atomic(page); + ret = CMPXCHG(&table[index], orig_pte, new_pte); + kunmap_atomic(table); + + kvm_release_page_dirty(page); + } else { + struct vm_area_struct *vma; + unsigned long vaddr = (unsigned long)ptep_user & PAGE_MASK; + unsigned long pfn; + unsigned long paddr; + + down_read(¤t->mm->mmap_sem); + vma = find_vma_intersection(current->mm, vaddr, vaddr + PAGE_SIZE); + if (!vma || !(vma->vm_flags & VM_PFNMAP)) { + up_read(¤t->mm->mmap_sem); + return -EFAULT; + } + pfn = ((vaddr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; + paddr = pfn << PAGE_SHIFT; + table = memremap(paddr, PAGE_SIZE, MEMREMAP_WB); + if (!table) { + up_read(¤t->mm->mmap_sem); + return -EFAULT; + } + ret = CMPXCHG(&table[index], orig_pte, new_pte); + memunmap(table); + up_read(¤t->mm->mmap_sem); + } return (ret != orig_pte); } -- 2.7.4