From patchwork Wed Sep 27 08:04:21 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexandru Stefan ISAILA X-Patchwork-Id: 9973373 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 1F53E60375 for ; Wed, 27 Sep 2017 08:08:05 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 10D7A28554 for ; Wed, 27 Sep 2017 08:08:05 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 0585529109; Wed, 27 Sep 2017 08:08:05 +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=-4.1 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_MED,T_DKIM_INVALID autolearn=ham version=3.3.1 Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 0188028554 for ; Wed, 27 Sep 2017 08:08:01 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dx7KY-0005A7-D7; Wed, 27 Sep 2017 08:04:30 +0000 Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xenproject.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dx7KX-00059z-8t for xen-devel@lists.xen.org; Wed, 27 Sep 2017 08:04:29 +0000 Received: from [85.158.137.68] by server-6.bemta-3.messagelabs.com id 2C/7F-02225-C8B5BC95; Wed, 27 Sep 2017 08:04:28 +0000 X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFupikeJIrShJLcpLzFFi42KJPp7RqtsdfTr SoHOShsWSj4tZHBg9ju7+zRTAGMWamZeUX5HAmvHoUQN7QZdLxao77YwNjO0mXYycHMwC1hK9 /5oZuxi5OFgEmlkk3l1cA+X8ZJb49aqbrYuRg0NIwEOi66YhSFxIYAGjxJuNM6Di7hJXHluAD BISWMYose+KLojNJmAg8errN0YQW0RAWuLa58uMEMsqJLZP2ssC0ios4CVx40IiSJhFQFVi+Z UdYCW8QBN/P29nAbElBOQkbp7rZJ7AyLeAkWEVo3pxalFZapGuiV5SUWZ6RkluYmaOrqGBsV5 uanFxYnpqTmJSsV5yfu4mRmCIMADBDsbGL06HGCU5mJREeev9T0cK8SXlp1RmJBZnxBeV5qQW H2KU4eBQkuD9EAWUEyxKTU+tSMvMAQYrTFqCg0dJhDcbJM1bXJCYW5yZDpE6xWjMcWzT5T9MH B037/5hEmLJy89LlRLn/QpSKgBSmlGaBzcIFkWXGGWlhHkZgU4T4ilILcrNLEGVf8UozsGoJM y7HWQKT2ZeCdy+V0CnMAGd0jv1BMgpJYkIKakGxuWJk93mB1poXWyRPB7AzbFZXTrsz4ddzFU f+2qYD6+dviv51PlPf9Okeac+uZ1cx/DptbrMps25y3fbcNwqXyapZ25eZ/R3uvbjylt2xrKi SwwYtkpHXSrNLnNT5NfZWduyhnuL4JT6t25CPC3xacz7dsRnH7JferM+kO1b71v9uAkPzT7eV mIpzkg01GIuKk4EAHlnAaGdAgAA X-Env-Sender: aisaila@bitdefender.com X-Msg-Ref: server-4.tower-31.messagelabs.com!1506499467!58631139!1 X-Originating-IP: [91.199.104.133] X-SpamReason: No, hits=0.0 required=7.0 tests= X-StarScan-Received: X-StarScan-Version: 9.4.45; banners=-,-,- X-VirusChecked: Checked Received: (qmail 32030 invoked from network); 27 Sep 2017 08:04:27 -0000 Received: from mx02.bbu.dsd.mx.bitdefender.com (HELO mx02.buh.bitdefender.com) (91.199.104.133) by server-4.tower-31.messagelabs.com with DHE-RSA-AES128-GCM-SHA256 encrypted SMTP; 27 Sep 2017 08:04:27 -0000 Comment: DomainKeys? See http://domainkeys.sourceforge.net/ DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=default; d=bitdefender.com; b=LMvh0YMKwU93O++7JQXoBStrfYuBScm0gcsJP5llgyO0aWmrU0ec8AYIii/FTgwHbJ0GzgQXx5dtgXSyw9LaMXwbbVw5NvFFjVmwcBVPNTeD1ulGfOYyTxBfNkEssVk6DTrESToeKpXD04bkTHyBMWa+rAsWV+sCswyycyWYn8JarDVj+q16t+ueY1YPoiGuDF2unDbh7+YaXADNgdK3PfbozRtMykm82KXSg8bojFRjPVWylaW/Ue7ZQgD9IQa2xjO90w8gesTFWH1UnXZk1IvQj2JDqFyDEvyX9IASP47A01hIb9nvrArT0cpyXGiiAoG1feLm34FHQ5T1VtSWyQ==; h=Received:Received:Received:Received:From:To:Cc:Subject:Date:Message-Id:X-Mailer; DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=bitdefender.com; h=from:to :cc:subject:date:message-id; s=default; bh=/BgXhjHaEh5KIR6fQh9QA cYR9cg=; b=KdUHPRTosa5gdHAId+dpSDVuAxLorjaRQvB70EjQZRqHEVtcRYvV3 zkYfBVlIOlZ3j4GcxkFhNW/35Yj81z6xFeHS1k3IeF4DftTsf29Nc0TWV1Gcjm9i rmhkUoLghrVZ57L4vHx2E/iOMUk+ZrZLTHhLZu7h1pPlOKGZSIcfZi6tB2Wqfj4q VdPguRx18yzntw6HKGV4Z/AZ55rlJIT6A+2SdCt6TmWU+bJRAHPsrpqtYQAussWi YfrAdOMj4Vi+I9xbCtSfLfB010Yg2rslrP0SVloakfwX3YKNnIAGHVsylJhE6Qjv jG1FA0+MV608sEIx3+cdvILwr/pRl0Z7Q== Received: (qmail 25839 invoked from network); 27 Sep 2017 11:04:26 +0300 Received: from mx01robo.bbu.dsd.mx.bitdefender.com (10.17.80.60) by mx02.buh.bitdefender.com with AES128-GCM-SHA256 encrypted SMTP; 27 Sep 2017 11:04:26 +0300 Received: (qmail 6588 invoked from network); 27 Sep 2017 11:04:26 +0300 Received: from unknown (HELO aisaila-Latitude-E5570.dsd.bitdefender.biz) (10.10.195.54) by mx01robo.bbu.dsd.mx.bitdefender.com with SMTP; 27 Sep 2017 11:04:26 +0300 From: Alexandru Isaila To: xen-devel@lists.xen.org Date: Wed, 27 Sep 2017 11:04:21 +0300 Message-Id: <1506499461-15603-1-git-send-email-aisaila@bitdefender.com> X-Mailer: git-send-email 2.7.4 Cc: Alexandru Isaila , andrew.cooper3@citrix.com, paul.durrant@citrix.com, jbeulich@suse.com Subject: [Xen-devel] [PATCH v5] x86/hvm: Implement hvmemul_write() using real mappings X-BeenThere: xen-devel@lists.xen.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: xen-devel-bounces@lists.xen.org Sender: "Xen-devel" X-Virus-Scanned: ClamAV using ClamSMTP From: Andrew Cooper An access which crosses a page boundary is performed atomically by x86 hardware, albeit with a severe performance penalty. An important corner case is when a straddled access hits two pages which differ in whether a translation exists, or in net access rights. The use of hvm_copy*() in hvmemul_write() is problematic, because it performs a translation then completes the partial write, before moving onto the next translation. If an individual emulated write straddles two pages, the first of which is writable, and the second of which is not, the first half of the write will complete before #PF is raised from the second half. This results in guest state corruption as a side effect of emulation, which has been observed to cause windows to crash while under introspection. Introduce the hvmemul_{,un}map_linear_addr() helpers, which translate an entire contents of a linear access, and vmap() the underlying frames to provide a contiguous virtual mapping for the emulator to use. This is the same mechanism as used by the shadow emulation code. This will catch any translation issues and abort the emulation before any modifications occur. Signed-off-by: Andrew Cooper Signed-off-by: Alexandru Isaila --- Changes since V4: - Moved the mfn increment line back - Removed the new line between mfn++ and while Reviewed-by: Paul Durrant --- xen/arch/x86/hvm/emulate.c | 174 ++++++++++++++++++++++++++++++++++---- xen/include/asm-x86/hvm/emulate.h | 7 ++ 2 files changed, 164 insertions(+), 17 deletions(-) diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c index cc874ce..9d8be30 100644 --- a/xen/arch/x86/hvm/emulate.c +++ b/xen/arch/x86/hvm/emulate.c @@ -498,6 +498,156 @@ static int hvmemul_do_mmio_addr(paddr_t mmio_gpa, } /* + * Map the frame(s) covering an individual linear access, for writeable + * access. May return NULL for MMIO, or ERR_PTR(~X86EMUL_*) for other errors + * including ERR_PTR(~X86EMUL_OKAY) for write-discard mappings. + * + * In debug builds, map() checks that each slot in hvmemul_ctxt->mfn[] is + * clean before use, and poisions unused slots with INVALID_MFN. + */ +static void *hvmemul_map_linear_addr( + unsigned long linear, unsigned int bytes, uint32_t pfec, + struct hvm_emulate_ctxt *hvmemul_ctxt) +{ + struct vcpu *curr = current; + void *err, *mapping; + + /* First and final gfns which need mapping. */ + unsigned long frame = linear >> PAGE_SHIFT, first = frame; + unsigned long final = (linear + bytes - !!bytes) >> PAGE_SHIFT; + + /* + * mfn points to the next free slot. All used slots have a page reference + * held on them. + */ + mfn_t *mfn = &hvmemul_ctxt->mfn[0]; + + /* + * The caller has no legitimate reason for trying a zero-byte write, but + * final is calculate to fail safe in release builds. + * + * The maximum write size depends on the number of adjacent mfns[] which + * can be vmap()'d, accouting for possible misalignment within the region. + * The higher level emulation callers are responsible for ensuring that + * mfns[] is large enough for the requested write size. + */ + if ( bytes == 0 || + final - first >= ARRAY_SIZE(hvmemul_ctxt->mfn) ) + { + ASSERT_UNREACHABLE(); + goto unhandleable; + } + + do { + enum hvm_translation_result res; + struct page_info *page; + pagefault_info_t pfinfo; + p2m_type_t p2mt; + + /* Error checking. Confirm that the current slot is clean. */ + ASSERT(mfn_x(*mfn) == 0); + + res = hvm_translate_get_page(curr, frame << PAGE_SHIFT, true, pfec, + &pfinfo, &page, NULL, &p2mt); + + switch ( res ) + { + case HVMTRANS_okay: + break; + + case HVMTRANS_bad_linear_to_gfn: + x86_emul_pagefault(pfinfo.ec, pfinfo.linear, &hvmemul_ctxt->ctxt); + err = ERR_PTR(~X86EMUL_EXCEPTION); + goto out; + + case HVMTRANS_bad_gfn_to_mfn: + err = NULL; + goto out; + + case HVMTRANS_gfn_paged_out: + case HVMTRANS_gfn_shared: + err = ERR_PTR(~X86EMUL_RETRY); + goto out; + + default: + goto unhandleable; + } + + *mfn++ = _mfn(page_to_mfn(page)); + + if ( p2m_is_discard_write(p2mt) ) + { + err = ERR_PTR(~X86EMUL_OKAY); + goto out; + } + + } while ( ++frame < final ); + + /* Entire access within a single frame? */ + if ( first == final ) + mapping = map_domain_page(hvmemul_ctxt->mfn[0]); + /* Multiple frames? Need to vmap(). */ + else if ( (mapping = vmap(hvmemul_ctxt->mfn, + final - first + 1)) == NULL ) + goto unhandleable; + +#ifndef NDEBUG /* Poision unused mfn[]s with INVALID_MFN. */ + while ( mfn < hvmemul_ctxt->mfn + ARRAY_SIZE(hvmemul_ctxt->mfn) ) + { + ASSERT(mfn_x(*mfn) == 0); + *mfn++ = INVALID_MFN; + } +#endif + + return mapping + (linear & ~PAGE_MASK); + + unhandleable: + err = ERR_PTR(~X86EMUL_UNHANDLEABLE); + + out: + /* Drop all held references. */ + while ( mfn-- > hvmemul_ctxt->mfn ) + put_page(mfn_to_page(mfn_x(*mfn))); + + return err; +} + +static void hvmemul_unmap_linear_addr( + void *mapping, unsigned long linear, unsigned int bytes, + struct hvm_emulate_ctxt *hvmemul_ctxt) +{ + struct domain *currd = current->domain; + unsigned long frame = linear >> PAGE_SHIFT; + unsigned long final = (linear + bytes - !!bytes) >> PAGE_SHIFT; + mfn_t *mfn = &hvmemul_ctxt->mfn[0]; + + ASSERT(bytes > 0); + + if ( frame == final ) + unmap_domain_page(mapping); + else + vunmap(mapping); + + do + { + ASSERT(mfn_valid(*mfn)); + paging_mark_dirty(currd, *mfn); + put_page(mfn_to_page(mfn_x(*mfn))); + + *mfn++ = _mfn(0); /* Clean slot for map()'s error checking. */ + } while ( ++frame < final ); + + +#ifndef NDEBUG /* Check (and clean) all unused mfns. */ + while ( mfn < hvmemul_ctxt->mfn + ARRAY_SIZE(hvmemul_ctxt->mfn) ) + { + ASSERT(mfn_eq(*mfn, INVALID_MFN)); + *mfn++ = _mfn(0); + } +#endif +} + +/* * Convert addr from linear to physical form, valid over the range * [addr, addr + *reps * bytes_per_rep]. *reps is adjusted according to * the valid computed range. It is always >0 when X86EMUL_OKAY is returned. @@ -988,11 +1138,11 @@ static int hvmemul_write( struct hvm_emulate_ctxt *hvmemul_ctxt = container_of(ctxt, struct hvm_emulate_ctxt, ctxt); struct vcpu *curr = current; - pagefault_info_t pfinfo; unsigned long addr, reps = 1; uint32_t pfec = PFEC_page_present | PFEC_write_access; struct hvm_vcpu_io *vio = &curr->arch.hvm_vcpu.hvm_io; int rc; + void *mapping; if ( is_x86_system_segment(seg) ) pfec |= PFEC_implicit; @@ -1008,23 +1158,13 @@ static int hvmemul_write( (vio->mmio_gla == (addr & PAGE_MASK)) ) return hvmemul_linear_mmio_write(addr, bytes, p_data, pfec, hvmemul_ctxt, 1); - rc = hvm_copy_to_guest_linear(addr, p_data, bytes, pfec, &pfinfo); + mapping = hvmemul_map_linear_addr(addr, bytes, pfec, hvmemul_ctxt); + if ( IS_ERR(mapping) ) + return ~PTR_ERR(mapping); - switch ( rc ) - { - case HVMTRANS_okay: - break; - case HVMTRANS_bad_linear_to_gfn: - x86_emul_pagefault(pfinfo.ec, pfinfo.linear, &hvmemul_ctxt->ctxt); - return X86EMUL_EXCEPTION; - case HVMTRANS_bad_gfn_to_mfn: - return hvmemul_linear_mmio_write(addr, bytes, p_data, pfec, hvmemul_ctxt, 0); - case HVMTRANS_gfn_paged_out: - case HVMTRANS_gfn_shared: - return X86EMUL_RETRY; - default: - return X86EMUL_UNHANDLEABLE; - } + memcpy(mapping, p_data, bytes); + + hvmemul_unmap_linear_addr(mapping, addr, bytes, hvmemul_ctxt); return X86EMUL_OKAY; } diff --git a/xen/include/asm-x86/hvm/emulate.h b/xen/include/asm-x86/hvm/emulate.h index 8864775..d379a4a 100644 --- a/xen/include/asm-x86/hvm/emulate.h +++ b/xen/include/asm-x86/hvm/emulate.h @@ -37,6 +37,13 @@ struct hvm_emulate_ctxt { unsigned long seg_reg_accessed; unsigned long seg_reg_dirty; + /* + * MFNs behind temporary mappings in the write callback. The length is + * arbitrary, and can be increased if writes longer than PAGE_SIZE+1 are + * needed. + */ + mfn_t mfn[2]; + uint32_t intr_shadow; bool_t set_context;