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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 C2F7FC43441 for ; Wed, 21 Nov 2018 10:10:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 918F720989 for ; Wed, 21 Nov 2018 10:10:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 918F720989 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729014AbeKUUoR convert rfc822-to-8bit (ORCPT ); Wed, 21 Nov 2018 15:44:17 -0500 Received: from prv1-mh.provo.novell.com ([137.65.248.33]:36036 "EHLO prv1-mh.provo.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726048AbeKUUoR (ORCPT ); Wed, 21 Nov 2018 15:44:17 -0500 Received: from INET-PRV1-MTA by prv1-mh.provo.novell.com with Novell_GroupWise; Wed, 21 Nov 2018 03:10:27 -0700 Message-Id: <5BF52F0E02000078001FE5BE@prv1-mh.provo.novell.com> X-Mailer: Novell GroupWise Internet Agent 18.1.0 Date: Wed, 21 Nov 2018 03:10:22 -0700 From: "Jan Beulich" To: , , Cc: "Andrew Lutomirski" , "xen-devel" , "Boris Ostrovsky" , "Juergen Gross" , Subject: [PATCH v2] x86-64/Xen: fix stack switching References: <5AF03EBD02000078001C1303@prv1-mh.provo.novell.com> <5AF03EBD02000000000F91D6@prv1-mh.provo.novell.com> <5AF03EBD02000078001FE590@prv1-mh.provo.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org While in the native case entry into the kernel happens on the trampoline stack, PV Xen kernels get entered with the current thread stack right away. Hence source and destination stacks are identical in that case, and special care is needed. Other than in sync_regs() the copying done on the INT80 path as well as on the NMI path itself isn't NMI / #MC safe, as either of these events occurring in the middle of the stack copying would clobber data on the (source) stack. (Of course, in the NMI case only #MC could break things.) I'm not altering the similar code in interrupt_entry(), as that code path is unreachable afaict when running PV Xen guests. Fixes: 7f2590a110b837af5679d08fc25c6227c5a8c497 Signed-off-by: Jan Beulich Cc: stable@kernel.org --- v2: Correct placement of .Lint80_keep_stack label. --- arch/x86/entry/entry_64.S | 8 ++++++++ arch/x86/entry/entry_64_compat.S | 10 ++++++++-- 2 files changed, 16 insertions(+), 2 deletions(-) --- 4.20-rc3/arch/x86/entry/entry_64.S +++ 4.20-rc3-x86_64-stack-switch-Xen/arch/x86/entry/entry_64.S @@ -1380,6 +1380,12 @@ ENTRY(nmi) swapgs cld SWITCH_TO_KERNEL_CR3 scratch_reg=%rdx + + movq PER_CPU_VAR(cpu_current_top_of_stack), %rdx + subq $8, %rdx + xorq %rsp, %rdx + shrq $PAGE_SHIFT, %rdx + jz .Lnmi_keep_stack movq %rsp, %rdx movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp UNWIND_HINT_IRET_REGS base=%rdx offset=8 @@ -1389,6 +1395,8 @@ ENTRY(nmi) pushq 2*8(%rdx) /* pt_regs->cs */ pushq 1*8(%rdx) /* pt_regs->rip */ UNWIND_HINT_IRET_REGS +.Lnmi_keep_stack: + pushq $-1 /* pt_regs->orig_ax */ PUSH_AND_CLEAR_REGS rdx=(%rdx) ENCODE_FRAME_POINTER --- 4.20-rc3/arch/x86/entry/entry_64_compat.S +++ 4.20-rc3-x86_64-stack-switch-Xen/arch/x86/entry/entry_64_compat.S @@ -361,17 +361,23 @@ ENTRY(entry_INT80_compat) /* Need to switch before accessing the thread stack. */ SWITCH_TO_KERNEL_CR3 scratch_reg=%rdi + + movq PER_CPU_VAR(cpu_current_top_of_stack), %rdi + subq $8, %rdi + xorq %rsp, %rdi + shrq $PAGE_SHIFT, %rdi + jz .Lint80_keep_stack movq %rsp, %rdi movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp - pushq 6*8(%rdi) /* regs->ss */ pushq 5*8(%rdi) /* regs->rsp */ pushq 4*8(%rdi) /* regs->eflags */ pushq 3*8(%rdi) /* regs->cs */ pushq 2*8(%rdi) /* regs->ip */ pushq 1*8(%rdi) /* regs->orig_ax */ - pushq (%rdi) /* pt_regs->di */ +.Lint80_keep_stack: + pushq %rsi /* pt_regs->si */ xorl %esi, %esi /* nospec si */ pushq %rdx /* pt_regs->dx */