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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 05517C76190 for ; Mon, 15 Jul 2019 09:07:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CCA3120838 for ; Mon, 15 Jul 2019 09:07:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729600AbfGOJHc (ORCPT ); Mon, 15 Jul 2019 05:07:32 -0400 Received: from mail-wr1-f68.google.com ([209.85.221.68]:36051 "EHLO mail-wr1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729394AbfGOJHc (ORCPT ); Mon, 15 Jul 2019 05:07:32 -0400 Received: by mail-wr1-f68.google.com with SMTP id n4so16233455wrs.3 for ; Mon, 15 Jul 2019 02:07:30 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:openpgp:message-id :date:user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=iIpNhGzg6P5/kknOVL3At51YBOM3pwLE0ZzAOv+ZuqM=; b=hUEG2sYiNOdw0k+VVRJS1sxtxUzdYY4b+GXaSgmVyWgFUGiaNxtSWxUj8ASkPdITq+ NeAPh7v61A5sQBhUTWbC/v7RcNBHtth/Qyh7rVvzOkubbxpZQYLD9YosYwh5qn14vuZR HOWgPEnXsW/v+PYUAllYN64Xic9K6rCrnh98KTHyodGArIxxHV2nAIgCAuDj3IFsGLZa tl0DKvx+WO2BXTOGPX6AsBeK/my8peliv8DGKRc+Jqt7ZFpPA1vgycqxJyBWL+6Oe2Ya E3eAT1rJ3zKm76WQKsnCRFtbSnxDqmNQh+ap6vrhUFZnHFr8TELo7UHTpShDdxwM0rbU IPZg== X-Gm-Message-State: APjAAAXSci9lgBRoZKIVnSmFEgYyqb4nd5TPmOuSpj4pqgtk7awYsX3D niHc5XOs2kBY3e4zDzYYY1wiAg== X-Google-Smtp-Source: APXvYqyaZd+NyYvWPkdjEU1+MpmkHgjx4zJEDQ81Tovwqc2sbwpA8fHg9HbrB24JFIfbbprCMrzmQg== X-Received: by 2002:adf:ea88:: with SMTP id s8mr23565961wrm.68.1563181650201; Mon, 15 Jul 2019 02:07:30 -0700 (PDT) Received: from ?IPv6:2001:b07:6468:f312:e983:8394:d6:a612? ([2001:b07:6468:f312:e983:8394:d6:a612]) by smtp.gmail.com with ESMTPSA id x185sm8422412wmg.46.2019.07.15.02.07.29 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Mon, 15 Jul 2019 02:07:29 -0700 (PDT) Subject: Re: [PATCH 04/22] x86/kvm: Don't call kvm_spurious_fault() from .fixup To: Josh Poimboeuf , x86@kernel.org Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Thomas Gleixner , Nick Desaulniers , Arnd Bergmann , Jann Horn , Randy Dunlap , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= References: <1f37a9e42732c224bc5299dbc827b4101c9deb22.1563150885.git.jpoimboe@redhat.com> From: Paolo Bonzini Openpgp: preference=signencrypt Message-ID: <07b8513a-d8f7-f8cf-daf6-83a80ade987a@redhat.com> Date: Mon, 15 Jul 2019 11:07:28 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <1f37a9e42732c224bc5299dbc827b4101c9deb22.1563150885.git.jpoimboe@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 15/07/19 02:36, Josh Poimboeuf wrote: > After making a change to improve objtool's sibling call detection, it > started showing the following warning: > > arch/x86/kvm/vmx/nested.o: warning: objtool: .fixup+0x15: sibling call from callable instruction with modified stack frame > > The problem is the ____kvm_handle_fault_on_reboot() macro. It does a > fake call by pushing a fake RIP and doing a jump. That tricks the > unwinder into printing the function which triggered the exception, > rather than the .fixup code. > > Instead of the hack to make it look like the original function made the > call, just change the macro so that the original function actually does > make the call. This allows removal of the hack, and also makes objtool > happy. > > I triggered a vmx instruction exception and verified that the stack > trace is still sane: > > kernel BUG at arch/x86/kvm/x86.c:358! > invalid opcode: 0000 [#1] SMP PTI > CPU: 28 PID: 4096 Comm: qemu-kvm Not tainted 5.2.0+ #16 > Hardware name: Lenovo THINKSYSTEM SD530 -[7X2106Z000]-/-[7X2106Z000]-, BIOS -[TEE113Z-1.00]- 07/17/2017 > RIP: 0010:kvm_spurious_fault+0x5/0x10 > Code: 00 00 00 00 00 8b 44 24 10 89 d2 45 89 c9 48 89 44 24 10 8b 44 24 08 48 89 44 24 08 e9 d4 40 22 00 0f 1f 40 00 0f 1f 44 00 00 <0f> 0b 66 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 41 55 49 89 fd 41 > RSP: 0018:ffffbf91c683bd00 EFLAGS: 00010246 > RAX: 000061f040000000 RBX: ffff9e159c77bba0 RCX: ffff9e15a5c87000 > RDX: 0000000665c87000 RSI: ffff9e15a5c87000 RDI: ffff9e159c77bba0 > RBP: 0000000000000000 R08: 0000000000000000 R09: ffff9e15a5c87000 > R10: 0000000000000000 R11: fffff8f2d99721c0 R12: ffff9e159c77bba0 > R13: ffffbf91c671d960 R14: ffff9e159c778000 R15: 0000000000000000 > FS: 00007fa341cbe700(0000) GS:ffff9e15b7400000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007fdd38356804 CR3: 00000006759de003 CR4: 00000000007606e0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > PKRU: 55555554 > Call Trace: > loaded_vmcs_init+0x4f/0xe0 > alloc_loaded_vmcs+0x38/0xd0 > vmx_create_vcpu+0xf7/0x600 > kvm_vm_ioctl+0x5e9/0x980 > ? __switch_to_asm+0x40/0x70 > ? __switch_to_asm+0x34/0x70 > ? __switch_to_asm+0x40/0x70 > ? __switch_to_asm+0x34/0x70 > ? free_one_page+0x13f/0x4e0 > do_vfs_ioctl+0xa4/0x630 > ksys_ioctl+0x60/0x90 > __x64_sys_ioctl+0x16/0x20 > do_syscall_64+0x55/0x1c0 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > RIP: 0033:0x7fa349b1ee5b > > Signed-off-by: Josh Poimboeuf > --- > Cc: Paolo Bonzini > Cc: Radim Krčmář > --- > arch/x86/include/asm/kvm_host.h | 33 ++++++++++++++++++--------------- > 1 file changed, 18 insertions(+), 15 deletions(-) > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index 0cc5b611a113..af7e18c05f98 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -1499,22 +1499,25 @@ enum { > /* > * Hardware virtualization extension instructions may fault if a > * reboot turns off virtualization while processes are running. > - * Trap the fault and ignore the instruction if that happens. > + * If that happens, trap the fault and panic (unless we're rebooting). Not sure the comment is better than before, but apar from that Acked-by: Paolo Bonzini Thanks for the cleanups! Paolo > */ > -asmlinkage void kvm_spurious_fault(void); > - > -#define ____kvm_handle_fault_on_reboot(insn, cleanup_insn) \ > - "666: " insn "\n\t" \ > - "668: \n\t" \ > - ".pushsection .fixup, \"ax\" \n" \ > - "667: \n\t" \ > - cleanup_insn "\n\t" \ > - "cmpb $0, kvm_rebooting \n\t" \ > - "jne 668b \n\t" \ > - __ASM_SIZE(push) " $666b \n\t" \ > - "jmp kvm_spurious_fault \n\t" \ > - ".popsection \n\t" \ > - _ASM_EXTABLE(666b, 667b) > +asmlinkage void __noreturn kvm_spurious_fault(void); > + > +#define ____kvm_handle_fault_on_reboot(insn, cleanup_insn) \ > + "666: \n\t" \ > + insn "\n\t" \ > + "jmp 668f \n\t" \ > + "667: \n\t" \ > + "call kvm_spurious_fault \n\t" \ > + "668: \n\t" \ > + ".pushsection .fixup, \"ax\" \n\t" \ > + "700: \n\t" \ > + cleanup_insn "\n\t" \ > + "cmpb $0, kvm_rebooting\n\t" \ > + "je 667b \n\t" \ > + "jmp 668b \n\t" \ > + ".popsection \n\t" \ > + _ASM_EXTABLE(666b, 700b) > > #define __kvm_handle_fault_on_reboot(insn) \ > ____kvm_handle_fault_on_reboot(insn, "") >